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  • Articles  (8,723)
  • Springer  (8,723)
  • 1995-1999  (8,723)
  • Process Engineering, Biotechnology, Nutrition Technology  (8,723)
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  • Articles  (8,723)
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  • 1
    Electronic Resource
    Electronic Resource
    Bacterial complementation as a means to test enzyme–ligand interactions (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 181-186 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A bacterial complementation assay has been developed for the rapid screening of a large number of compounds to identify those that inhibit an enzyme target for structure-based inhibitor design. The target enzyme is the hypoxanthine phosphoribosyltransferase (HPRT). This enzyme has been proposed as a potential target for inhibitors that may be developed into drugs for the treatment of diseases caused by several parasites. The screening assay utilizes genetically deficient bacteria complemented by active, recombinant enzyme grown in selective medium in microtiter plates. By comparing absorbance measurements of bacteria grown in the presence and absence of test compounds, the effect of the compounds on bacterial growth can be rapidly assayed. IC50 values for inhibition of bacterial growth are a reflection of the ability of the compounds to bind and/or inhibit the recombinant enzyme. We have tested this bacterial complementation screening assay using recombinant HPRT from the parasites Plasmodium falciparum and Trypanosoma cruzi, as well as the human enzyme. The results of these studies demonstrate that a screening assay using bacterial complement selection can be used to identify compounds that target enzymes and can become an important part of structure-based drug design efforts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051274
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  • 2
    Electronic Resource
    Electronic Resource
    Photolimitation and photoinhibition as factors determining optimal dilution rate to produce eicosapentaenoic acid from cultures of the microalga Isochrysis galbana (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 199-205 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Eicosapentaenoic acid (EPA) productivity from continuous cultures of the marine microalga Isochrysis galbana was studied, taking into account the irradiance on the reactor surface, that is, the photolimitation/photoinhibition regime to which the cells are exposed. Experiments were conducted under a wide variety of operating conditions. The dilution rate ranged from 0.005 h−1 to 0.040 h−1 at five external irradiances (820, 1620, 2050, 2450 and 3270 μmol photons m−2 s−1) covering photolimited to photoinhibited growth. Under these conditions, the specific growth rate (μ) was found to be the main factor influencing EPA content (ranging from 2.35% to 5.23% dryweight) and productivity (up to 0.88 mg l−1 h−1). The fatty acid content was not significantly affected by the external irradiance, but was influenced by the state of growth of the microalga, depending on whether the light regime was photolimiting or photoinhibiting. It might be suggested that light should no longer be considered an isolated factor affecting EPA synthesis, but an indirect influence through the photolimitation/photoinhibition regime and growth rate. At a given dilution rate, EPA content and biomass concentration are lower under photoinhibiting external irradiances than those corresponding to photolimiting conditions, and consequently EPA productivity decays. Since the effect of photoinhibition is less marked at high biomass concentration, a strategy to optimize EPA productivity from microalgal cultures could consist of reducing the dilution rate when the external irradiance increases above the phoinhibition threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051277
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  • 3
    Electronic Resource
    Electronic Resource
    Biochemical basis for carbon monoxide tolerance and butanol production by Butyribacterium methylotrophicum (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 827-832 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The biochemical mechanisms for growth tolerance to a 100% CO headspace in cultures, and butanol plus ethanol production from CO by Butyribacterium methylotrophicum were assessed in the wild-type and CO-adapted strains. The CO-adapted strain grew on glucose or CO under a 100% CO headspace, whereas, the growth of the wild-type strain was severely inhibited by 100% CO. The CO-adapted strain, unlike the wild-type, also produced butyrate, from either pyruvate or CO. The CO-adapted strain was a metabolic mutant having higher levels of ferredoxin–NAD oxidoreductase activity, which was not inhibited by NADH. Consequently, only the CO-adapted strain can grow on CO because CO oxidation generates reduced ferredoxin which, via the mutated ferredoxin–NAD reductase activity, forms reduced NADH required for catabolism. When the CO-adapted strain was grown at pH 6.0 it produced butanol (0.33 g/l) and ethanol (0.5 g/l) from CO and the cells contained the following NAD-linked enzyme activities (μmol min−1 mg protein−1): butyraldehyde dehydrogenase (227), butanol dehydrogenase (686), acetaldehyde dehydrogenase (82) and ethanol dehydrogenase (129).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051469
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of optically active ethyl 4-chloro-3-hydroxybutanoate by microbial reduction (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 847-851 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A total of 400 yeast strains were examined for the ability to reduce ethyl 4-chloroacetoacetate (COBE) to ethyl 4-chloro-3-hydroxybutyrate (CHBE) by using acetone-dried cells in the presence of a coenzyme-recycling system in water/n-butyl acetate. We discovered some yeast strains that reduced COBE to (S)-CHBE. Heating of acetone-dried cells of the selected yeast strains increased the optical purity of the product. There may be several enzymes that can reduce COBE stereoselectively in the same yeast cells. The cultured broth of Candida magnoliae accumulated 90 g/l (S)-CHBE (96.6% enantiomeric excess, e.e.) in the presence of glucose, NADP and glucose dehydrogenase in n-butyl acetate. When these cells were heated, the stereoselectivity of the reduction increased to 99% e.e. (S)-CHBE is one of the useful chiral building blocks applicable to the synthesis of some pharmaceuticals. We expect that the cheap and industrial production of this important chiral compound will follow the discovery of this yeast strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051472
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  • 5
    Electronic Resource
    Electronic Resource
    Subcellular location of enzymes involved in oxidation of n-alkane by Cladosporium resinae (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 860-864 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract More than 70% of n-hexadecane-grown cells of Cladosporium resinae ATCC 22711 were converted to spheroplasts when they were treated with chitinase and lytic enzyme from Trichoderma harziamum. The light mitochondrial fraction, containing microbodies, mitochondria and vacuoles, was isolated from spheroplasts. Vacuoles in cells were demonstrated by the inability of acridine orange to stain organelles previously treated with 2.5 μM Bafilomycin A1, a vacuolar ATPase inhibitor. Microbodies, mitochondria and vacuoles were separated from the light mitochondrial fraction by self-generated density-gradient ultracentrifugation using iodixanol as gradient medium. NADH-dependent n-alkane monooxygenase activity and fatty alcohol oxidase activity were located in the cytoplasm and mitochondrial fractions respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051474
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  • 6
    Electronic Resource
    Electronic Resource
    Duplicated Clostridium thermocellum cellobiohydrolase gene encoding cellulosomal subunits S3 and S5 (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 852-859 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The upstream region of the cellobiohydrolase gene cbhA of Clostridium thermocellum F7 was sequenced. It was found that this region contains the previously sequenced gene celK encoding an enzyme closely related to CbhA (cellulosomal subunit S3). The presence of a putative transcription terminator in the 524-bp intergenic region indicates that celK and cbhA are not cotranscribed as an operon. Sequence comparison between the two cellobiohydrolases revealed high sequence conservation in the catalytic domain and in the N-terminal cellulose-binding domain (CBD) homologous to CBD family IV, which binds specifically to amorphous cellulose and soluble cellooligosaccharides. In contrast to CbhA, CelK lacks a family III CBD capable of binding to crystalline cellulose. By partial amino acid sequence determination CelK was shown to be identical to cellulosomal subunit S5. CelK and CbhA were found to be members of subfamily E1 of cellulase family E (glycosylhydrolase family 9). Sequence comparison of catalytic domains of family E1 cellulases with C. thermocellum CelD, a family E1 endoglucanase of known three-dimensional structure, revealed a significant variation in the lengths of substrate-binding loops connecting the helices of the (α/α)6 barrel fold. The extended loops of CelK and CbhA might form an active-site tunnel, as found in the catalytic domains of fungal cellobiohydrolases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051473
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  • 7
    Electronic Resource
    Electronic Resource
    Biodegradation of azo dyes in cocultures of anaerobic granular sludge with aerobic aromatic amine degrading enrichment cultures (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 865-871 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A prerequisite for the mineralization (complete biodegradation) of many azo dyes is a combination of reductive and oxidative steps. In this study, the biodegradation of two azo dyes, 4-phenylazophenol (4-PAP) and Mordant Yellow 10 (4-sulfophenylazo-salicylic acid; MY10), was evaluated in batch experiments where anaerobic and aerobic conditions were integrated by exposing anaerobic granular sludge to oxygen. Under these conditions, the azo dyes were reduced, resulting in a temporal accumulation of aromatic amines. 4-Aminophenol (4-AP) and aniline were detected from the reduction of 4-PAP. 5-Aminosalicylic acid (5-ASA) and sulfanilic acid (SA) were detected from the reduction of MY10. Subsequently, aniline was degraded further in the presence of oxygen by the facultative aerobic bacteria present in the anaerobic granular sludge. 5-ASA and SA were also degraded, if inocula from aerobic enrichment cultures were added to the batch experiments. Due to rapid autoxidation of 4-AP, no enrichment culture could be established for this compound. The results of this study indicate that aerobic enrichment cultures developed on aromatic amines combined with oxygen-tolerant anaerobic granular sludge can potentially be used to completely biodegrade azo dyes under integrated anaerobic/aerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051475
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  • 8
    Electronic Resource
    Electronic Resource
    Degradation of phosphonates by streptomycete isolates (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 872-876 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Wild-type Streptomyces sp. strains, able to utilise both naturally occurring and synthetic organophosphonates, were isolated. High levels of inorganic phosphate were necessary for their growth in complete medium as well as in medium, supplemented with phosphonates as the sole carbon or nitrogen source. Isolate StA expressed detectable enzymatic activity against 2-aminoethylphosphonate in vivo. Streptomycete StC had a surprising ability to degrade N-phosphonomethylglycine (glyphosate) in a phosphate-independent manner via C–P bond cleavage accompanied by sarcosine formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051476
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  • 9
    Electronic Resource
    Electronic Resource
    Bioremediation of atrazine-contaminated soil by repeated applications of atrazine-degrading bacteria (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 877-882 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Bioaugmentation has previously been unreliable for the in situ clean-up of contaminated soils because of problems with poor survival and the rapid decline in activity of the bacterial inoculum. In an attempt to solve these problems, a 500-l batch fermenter was investigated for its ability to deliver inoculum repeatedly to contaminated soils via irrigation lines. In a field experiment, mesocosms were filled with 350 kg soil containing 100 mg kg−1 atrazine, and inoculated one, four or eight times with an atrazine-degrading bacterial consortium that was produced in the fermenter. After 12 weeks, no significant degradation of atrazine had occurred in soil that was inoculated only once; whereas, mesocosms inoculated four and eight times mineralized 38% and 72% of the atrazine respectively. Similar results were obtained in a laboratory experiment using soil contaminated with 100 mg kg−1 [14C]atrazine. After 35 days, soil that was inoculated once with 108 cfu ml−1 of the consortium or with the atrazine-degrading bacterium, Pseudomonas sp. strain ADP, mineralized 17% and 35% of the atrazine respectively. In comparison, microcosms inoculated every 3 days with the consortium or with Pseudomonas sp. (ADP) mineralized 64% or 90% of the atrazine over this same period. Results of these experiments suggest that repeated inoculation from an automated fermenter may provide a strategy for bioaugmentation of contaminated soil with xenobiotic-degrading bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051477
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  • 10
    Electronic Resource
    Electronic Resource
    Solid matrix characterization of immobilized Pseudomonas putida MTCC 1194 used for phenol degradation (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 891-895 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Characterization studies of calcium alginate beads with encapsulated Pseudomonas putida MTCC 1194, used for the biodegradation of phenol, were carried out to investigate the reactivity, reusability and structural strength of the solid matrix. Various techniques were employed to improve the structural stability of the immobilized solid necessary for its use in commercial reactors like packed bed flow reactor, fluidized bed and CSTR systems. Experiments were performed to establish the optimum conditions for durability, strength and steady biochemical reactivity. During a batch run of 40 h a gradual decline in the rate of phenol degradation was observed with the immobilized system. The calcium alginate beads with high structural strength yielded decreased activity. Treatment with a hardening agent like glutaraldehyde for different concentrations and treatment times led to variations in structural stability, reusability and the extent of phenol degradation. Scanning electron microscope studies of the immobilized solid indicated the internal distribution pattern of the cells encapsulated in a calcium alginate bead.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051479
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  • 11
    Electronic Resource
    Electronic Resource
    Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 883-890 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth on lysates). Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability. Gentle treatment conditions produced the best results. Complete cell deactivation was obtained for temperatures higher than 55 °C. The release kinetics were similar for temperatures varying from 60 °C to 100 °C. A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon. In thermal-chemical hydrolysis, NaOH was the most efficient for inducing cell lysis. Carbon release was a two-step process. First an immediate release occurred, which was of the same order of magnitude for A. eutrophus and sludge [100–200 mg dissolved organic C (DOC) g total suspended solids (TSS)−1], followed by a post-treatment release. The second step was virtually equivalent to the first for sludge, and weaker for A. eutrophus (〈50 mg DOC g TSS−1). The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated. The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h. The most consistent lysis and biodegradation results occurred at pH 10 and 60 °C after a 20-min incubation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051478
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  • 12
    Electronic Resource
    Electronic Resource
    EDITORIAL (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 1-1 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051480
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  • 13
    Electronic Resource
    Electronic Resource
    Fungal biosolubilization of Rhenish brown coal monitored by Curie-point pyrolysis/gas chromatography/mass spectrometry using tetraethylammonium hydroxide (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 41-48 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Residues and coal fractions that remained after the biosolubilization of Rhenish brown coal by strains of Lentinula edodes and Trametes versicolor have been studied by Curie-point pyrolysis/gas chromatography/mass spectrometry using tetraethylammonium hydroxide (NEt4OH) at 610 °C. To differentiate methyl derivatives of esters and ethers from free or bound hydroxyl and carboxyl groups NEt4OH was used in the thermochemolysis experiments instead the commonly used tetramethylammonium hydroxide. A comparison of humic acid fractions before and after fungal attack shows considerable alteration of the soluble macromolecules of coal. Depending on the coal fraction studied and the fungi used, the assortment of fatty acid esters released during the pyrolysis varies significantly. Furthermore, dicarbonic acid ethyl diesters as well as ethyl derivatives of aromatic ethers and acids yield information about humic acid structure and the biosolubilization of brown coal. Variations in the mixture produced are possibly caused by differences in the pattern of extracellular enzymes secreted that attack the macromolecular structural elements of brown coal. Therefore pyrolysis of native and microbiologically altered geomacromolecules using NEt4OH allows one to differentiate between free hydroxyl groups as well as substances that are attached to humic substances via ester or ether bridges, and their methylated counterparts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051484
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  • 14
    Electronic Resource
    Electronic Resource
    Biological processing of fossil fuels (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 2-15 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051481
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  • 15
    Electronic Resource
    Electronic Resource
    Biological processing of coal (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 16-24 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The irregular chemical structure of coal makes it an improbable substrate for bioconversion. Nevertheless, work completed in the last 20 years makes likely the development of practicable biological processes for beneficiation of low-rank coal and the conversion of low-rank coal to specific low-molecular-mass organic molecules and novel fluid fuels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051482
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  • 16
    Electronic Resource
    Electronic Resource
    Biotechnology and microbiology of coal degradation (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 25-40 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract For several years it has been known that fungi and bacteria can attack and even liquefy low rank coals. This review covers the progress in coal biotechnology and microbiology, mainly during the last decade, from describing the first effects to elucidating the mechanisms used by the microorganisms. More than one mechanism is responsible for microbial coal degradation/liquefaction: oxidative enzymes (peroxidases, laccases), hydrolytic enzymes (esterases), alkaline metabolites and natural chelators. Due to the heterogeneous structure of coal, which is described in one section, and for economic reasons the review focuses on the enzymatic depolymerization of brown coal. Approaches which seem not so promising are discussed (anaerobic, reductive pathways, chemical pretreatment). Finally the possible applications and products in this field are summarized, as lignite with a worldwide production of about 940 million tons a year will continue to play an important economic role in the future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051483
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  • 17
    Electronic Resource
    Electronic Resource
    Processes of liquefaction/solubilization of Spanish coals by microorganisms (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 49-56 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Several fundamental aspects of microbial coal liquefaction/solubilization were studied. The liquefied/solubilized products from coal by microorganisms were analysed. The liquid products analysed by IR titration and UV/visible spectrometry showed some alterations with regard to the original coal. Humic acids extracted from the liquefied lignite showed a reduction in the average molecular weight and a increase in the condensation index, probably due to depolymerization caused by microorganisms. The mechanisms implicated in coal biosolubilization by two fungal strains, M2 (Trichoderma sp.) and M4 (Penicillium sp.) were also studied. Extracellular peroxidase, esterase and phenoloxidase enzymes appear to be involved in coal solubilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051485
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  • 18
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    Mechanisms of coal solubilization by the deuteromycetes Trichoderma atroviride and Fusarium oxysporum (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 57-59 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Three different mechanisms can be envisaged that are used by fungi to solubilize coal: the production of alkaline substances, the extrusion of chelators and, of special interest in the scope of biotechnology, the action of enzymes. Whether these mechanisms are operating separately or in various combinations has not yet been finally assessed. The two deuteromycetes Fusarium oxysporum and Trichoderma atroviride solubilize coal by synergistic effects of various different mechanisms depending on the cell metabolism. F. oxysporum seems to solubilize coal by increasing the pH of the mycelial surroundings and by the action of chelators induced during growth in glutamate-containing media (without involvement of enzymes). T. atroviride, on the other hand, appears to use, in addition to an alkaline pH and a high chelator activity, at least two classes of enzyme activity to attack coal: hydrolytic activity for coal solubilization and ligninolytic activity for degradation of humic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051486
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  • 19
    Electronic Resource
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    In vivo-decolorization of coal-derived humic acids by laccase-excreting fungus Trametes versicolor (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 60-65 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Lignite (brown coal) can be liquefied/solubilized with several fungi by different mechanisms. When applied industrially, only catalytic mechanisms can compete with chemical methods. The well-known fungal ligninolytic peroxidases are at a disadvantage, in that the relatively expensive hydrogen peroxide must be used as a cofactor. Comparing several fungal strains, we observed that the fungus Trametes versicolor is able to decolorize coal-derived humic acids, producing a considerable amount of laccase in the process. During this reaction the amount of humic acids decreases whilst that of fulvic acids increases; this was verified by optical density measurement and GPC after the two substance classes had been separated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051487
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  • 20
    Electronic Resource
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    Evidence for and expression of a laccase gene in three basidiomycetes degrading humic acids (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 66-69 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The majority of lignin-degrading basidiomycetes are able to depolymerize humic acids. In this presentation the relationship and possible similarities between enzymes involved in lignin degradation and humic acid depolymerization were examined on the genetic level. We have cloned fragments of the gene encoding the extracellular ligninolytic enzyme laccase from Clitocybula dusenii, Nematoloma frowardii and a fungal strain designated i63-2, and compared the three sequences with those of several other published laccase genes. The sequenced fragments displayed a high homology both on the DNA (97%–77%) and amino acid (100%–85%) level. Furthermore, the expression of this gene in the above-mentioned fungi was demonstrated by a nested polymerase chain reaction with cDNA as template.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051488
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  • 21
    Electronic Resource
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    Transformation of macromolecules from a brown coal by lignin peroxidase (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 70-77 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Indirect evidence has suggested that lignin peroxidase (LiP) of the white-rot fungus Phanerochaete chrysosporium catalyses oxidative decolourisation and depolymerisation of macromolecules from brown coal in vivo. In this study we show that LiP catalyses these transformations in vitro. Unmethylated (USC45 coal) and methylated (MWSC6 coal) fractions of solubilised macromolecules (M r 〉 30 000) from a brown coal were treated with a semi-purified preparation of LiP isozymes from P. chrysosporium. Both coal fractions were decolourised, losing between 26% and 39% of their absorbance at both 280 nm and 400 nm, in reactions that had an absolute requirement for H2O2 and veratryl alcohol. Neither coal fraction was transformed when the enzyme was heat-inactivated or in the presence of the LiP inhibitor metavanadate. Gel-permeation chromatography showed that MWSC6 coal but not USC45 was depolymerised and yielded low-molecular-mass (M r 〈 30 000) fragments. Nine monomeric products were identified by GC-MS.
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    URL: http://dx.doi.org/10.1007/s002530051489
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  • 22
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    Degradation of alicyclic molecules by Rhodococcus ruber CD4 (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 85-90 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The present work describes investigations on the bacterial degradation of the alicyclic molecule cyclododecane. It represents a structure where the initial degradative steps have to be similar to a “subterminal” attack as there is no “terminal” part of the molecule. We were able to show that the gram-positive bacterium Rhodococcus ruber CD4 DSM 44394 oxidizes cyclododecane to the corresponding alcohol and ketone, the latter being subject to ring fission by a Baeyer-Villiger oxygenase. This key enzyme is an NADPH- and O2-dependent flavoprotein with a substrate specificity for bigger rings. The further metabolism of the resulting lactone gives rise to an ω-hydroxyalkanoic acid that is susceptible to common β-oxidation. Due to its alicyclic character and its ring size, cyclododecane is comparable to aliphatic bridge components that are an important element in the coal texture. They contribute to the three-dimensional coal structure and thus could serve as a valuable target for the oxidative abilities of R. ruber CD4 to reduce the molecular mass of coal.
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    Degradation of lignite (low-rank coal) by ligninolytic basidiomycetes and their manganese peroxidase system (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 78-84 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Ligninolytic basidiomycetes (wood and leaf-litter-decaying fungi) have the ability to degrade low-rank coal (lignite). Extracellular manganese peroxidase is the crucial enzyme in the depolymerization process of both coal-derived humic substances and native coal. The depolymerization of coal by Mn peroxidase is catalysed via chelated Mn(III) acting as a diffusible mediator with a high redox potential and can be enhanced in the presence of additional mediating agents (e.g. glutathione). The depolymerization process results in the formation of a complex mixture of lower-molecular-mass fulvic-acid-like compounds. Experiments using a synthetic 14C-labeled humic acid demonstrated that the Mn peroxidase-catalyzed depolymerization of humic substances was accompanied by a substantial release of carbon dioxide (17%–50% of the initially added radioactivity was released as 14CO2). Mn peroxidase was found to be a highly stable enzyme that remained active for several weeks under reaction conditions in a liquid reaction mixture and even persisted in sterile and native soil from an opencast mining area for some days.
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    Biosynthesis of polyhydroxyalkanoates from low-rank coal liquefaction products by Pseudomonas oleovorans and Rhodococcus ruber (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 91-95 
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    ISSN: 1432-0614
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A screening identified several bacteria that were able to use chemically heterogeneous low-rank coal liquefaction products as complex carbon sources for growth. Pseudomonas oleovorans and Rhodococcus ruber accumulated polyhydroxyalkanoic acids (PHA) amounting to 2%–8% of the cell dry weight when the cells were cultivated on these liquefaction products in the absence of any other carbon source. R. ruber accumulated, in addition to PHA, small amounts of triacylglycerols. The accumulated PHA consisted of 3-hydroxyhexanoate, 3-hydroxydecanoate, and 3-hydroxydodecanoate (P. oleovorans) or 3-hydroxybutyric acid and 3-hydroxyvaleric acid (R. ruber). Low-rank coal liquefaction products obtained from Trichoderma atroviride were better substrates for P. oleovorans than chemically produced fulvic acids.
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    EPR study and structural aspects of ferredoxins obtained from Thiobacillus ferrooxidans (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 96-98 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A comparison of iron-sulfur proteins obtained from Thiobacillus ferrooxidans was carried out. The microorganisms were grown on iron(II)- or sulfur-containing nutrients. In both cases different, broad elctron paramagnetic resonance (EPR) lines, originating from an iron(III) compound, were detected. Additional EPR lines of tetrahedral iron(III) and free radicals were observed. The UV spectra of these compounds also differ.
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    Effect of enclosing rocks and aeration on methanogenesis from coals (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 99-103 
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    Notes: Abstract Two coals of different rank, mined in Russia, were treated by an anaerobic methanogenic enrichment culture. The addition of alkaline enclosing rock to the lower-rank coal increased the pH of the incubation medium and methane production above that of the higher-rank coal with addition of its enclosing rock. This effect was accompanied by the leaching of cations from the incubation medium. The coal was processed without a preliminary chemical treatment in a two-stage aerobic/anaerobic bioreactor containing an anaerobic methanogenic granulated enrichment culture.
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    Intermediary sulfur compounds in pyrite oxidation: implications for bioleaching and biodepyritization of coal (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 104-110 
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    ISSN: 1432-0614
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    Notes: Abstract Accumulation of elemental sulfur during pyrite oxidation lowers the efficiency of coal desulfurization and bioleaching. In the case of pyrite bioleaching by Leptospirillum ferrooxidans, an iron(II)-ion-oxidizing organism without sulfur-oxidizing capacity, from the pyritic sulfur moiety about 10% elemental sulfur, 2% pentathionate, and 1% tetrathionate accumulated by a recently described cyclic pyrite oxidation mechanism. In the case of pure cultures of Thiobacillus ferrooxidans and mixed cultures of L. ferrooxidans and T. thiooxidans, pyrite was nearly completely oxidized to sulfate because of the capacity of these cultures to oxidize both iron(II) ions and sulfur compounds. Pyrite oxidation in acidic solutions, mediated chemically by iron(III) ion, resulted in an accumulation of similar amounts of sulfur compounds as obtained with L. ferrooxidans. Changes of pH to values below 2 or in the iron ion concentration are not decisive for diverting the flux of sulfur compounds. The literature on pyrite bioleaching is in agreement with the findings indicating that the chemistry of direct and indirect pyrite leaching is identical.
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    Developments in destructive and non-destructive pathways for selective desulfurizations in oil-biorefining processes (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 111-117 
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    ISSN: 1432-0614
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biocatalytic desulfurization is still not a commercial technology, but conceptual engineering and sensitivity analyses have shown that the approach is very promising. The purpose of this paper is to investigate further some aspects of the biodesulphurization pathways, discussing the non-destructive pathway with the well-known Rhodococcus rhodochrous IGTS8. Findings revealed byproducts, such as 2′-hydroxybiphenyl (HBP), sulfite and sulfate, obtained by the desulfurization of dibenzothiophene (DBT), to exert an inhibiting effect. The results suggest that IGTS8 may follow two different metabolic pathways in stationary-growth-phase cells or under growing conditions. The first pathway is characterized by oxidative steps, which convert DBT to DBT sulfoxide and to DBT sulfone. The sulfone is transformed to 2-(2′-hydroxyphenyl)benzene sulfinate and then to HBP and sulfite by a sulfinic acid hydrolase. In the second pathway the sulfone is further oxidized to 2-(2′-hydroxyphenyl)benzene sulfonate and then to HBP and sulfate by a sulfonic acid hydrolase. Experiments using benzene sulfonic acid suggest that the sulfonic acid hydrolase is an induced enzyme.
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    Bioremoval of organic and inorganic sulphur from coal samples (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 118-121 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The microbial ecology of different Spanish coal samples has been studied. Several bacteria have been isolated from enrichment cultures and characterised and their biodesulphurization abilities evaluated. Using morphological and physiological properties, different isolates have been related to species of the Xanthomonas, Pseudomonas, Chryseomonas and Moraxella genera. Some of the isolates, B(30)15 and T(30)10, gave important levels of organic desulphurization, close to 70%. Other isolates, B(30)7 and B(30)8, were able to remove inorganic sulphur with high efficiencies, over 67%. One of the isolates, B(30)10, metabolically related to Xanthomonas maltophila, was able to remove both organic and inorganic sulphur at neutral pH, with efficiencies of 69% and 68% respectively. The results obtained underline the potential use of some of these strains for industrial coal desulphurization processes.
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    Manipulation of the DNA coding for the desulphurizing activity in a new isolate of Arthrobacter sp. (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 122-126 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new bacterial strain able to cleave CS bonds from organosulphur heterocyclic compounds through the 4-S pathway and tentatively classified as Arthrobacter sp. was recently isolated. In the present short article we describe the cloning and the characterization of the DNA encoding the enzymes responsible for desulphurization in this microorganism, referred to as Arthrobacter sp. DS7. The desulphurization operon was found to be located in a large plasmid that also bears the genes conferring cadmium and arsenic resistance. By shortening this plasmid, a new cloning vector was prepared and used to obtain a recombinant derivative strain that desulphurizes dibenzothiophene despite of the presence of inorganic sulphur in the growth medium.
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    Acetate enhances solvent production and prevents degeneration in Clostridium beijerinckii BA101 (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 170-173 
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    Notes: Abstract Addition of sodium acetate to chemically defined MP2 medium was found to increase and stabilize solvent production by Clostridium beijerinckii BA101, a solvent-hyperproducing mutant derived from C. beijerinckii NCIMB 8052. C. beijerinckii BA101 demonstrated a greater increase in solvent production than C. beijerinckii NCIMB 8052 when sodium acetate was added to MP2 medium. In 1-l batch fermentations, C. beijerinckii BA101 produced 32.6 g/l total solvents, with butanol at 20.9 g/l, when grown in MP2 medium containing 60 mM sodium acetate and 8% glucose. To our knowledge, these values represent the highest solvent and butanol concentrations produced by a solventogenic Clostridium strain when grown in batch culture.
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    l-Glutamate and l-lysine: traditional products with impetuous developments (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 146-153 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Amino acids have been produced with the aid of microorganisms for nearly 40 years now. The economic importance of these cellular building blocks is enormous. Demand for them is rising continuously and currently more than 106 tonnes/year are required. Continual efforts to increase production performance are directed towards the microorganisms themselves, as well as towards technical improvements of the respective processes. A special position within the amino-acid-producing microorganisms is traditionally occupied by Corynebacterium glutamicum. Molecular research in conjunction with NMR studies of flux has revealed fascinating new properties of this particular organism, including the existence of a new type of exporter and reverse fluxes within the anaplerosis. The knowledge gained will enable the further improvement of production strains and furthermore extend fundamental insights into metabolite flux management within bacteria in general.
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    Simultaneous enzymatic wheat starch saccharification and fermentation to lactic acid by Lactococcus lactis (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 163-169 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Simultaneous saccharification of starch from whole-wheat flour and fermentation to lactic acid (SSF) was investigated. For saccharification the commercial enzyme mixture SAN Super 240 L, having α-amylase, amyloglucosidase and protease activity, was used, and Lactococcus lactis ssp. lactis ATCC 19435 was used for the fermentation. SSF was studied at flour concentrations corresponding to starch concentrations of 90 g/l and 180 g/l and SAN Super concentrations between 3 μl/g and 8 μl/g starch. Kinetic models, developed for the saccharification and fermentation, respectively, were used for simulation and data from SSF experiments were used for model verification. The model simulated SSF when sufficient amounts of nutrients were available during fermentation. This was achieved with high wheat flour concentrations or with addition of yeast extract or amino acids. Nutrient release was dependent on the level of enzyme activity.
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    Mechanism of l-methionine overproduction by Escherichia coli: the replacement of Ser-54 by Asn in the MetJ protein causes the derepression of l-methionine biosynthetic enzymes (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 179-185 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We derived l-methionine-analogue-resistant mutants from Escherichia coli JM109 strain by mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine and selected the potent l-methionine-overproducing strains by microbioassay using lactic acid bacteria. One of the mutants, strain TN1, produced approximately 910 mg l-methionine/l following the addition of 0.1% yeast extract to fundamental medium containing glucose and ammonium sulfate. The l-methionine biosynthetic enzymes, cystathionine γ-synthase and cystathionine β-lyase, of the l-methionine-overproducing mutants were little repressed by l-methionine. To analyse the mechanism of l-methionine overproduction in the mutant strains, the metJ gene coding for the E. colimet repressor, MetJ protein, was cloned and sequenced by the polymerase chain reaction. The same single-amino-acid subsitution (wild-type Ser → Asn) at position 54 was observed in four independent l-methionine-producing mutants. When the wild-type metJ gene was then introduced into strain TN1 having the mutant metJ gene, the level of enzyme synthesis and the l-methionine productivity in the transformants were found to revert to those of the wild-type. It was therefore considered that only one point mutation in the metJ gene occurred in the l-methionine-producing mutants. These results demonstrate the important role of residue 54 of the MetJ protein in l-methionine overproduction, probably because of the derepression of l-methionine biosynthetic enzymes.
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    Modulation of gene expression by (CA)n microsatellites in the filamentous ascomycete Podospora anserina (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 191-195 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A microsatellite consisting of the alternating pyrimidine-purine sequence (CA)n.(TG)n is found to occur in very conserved form in the genome of various races of the filamentous ascomycete Podospora anserina. Screening of a cDNA library revealed that this sequence is frequently transcribed. In this study, we focused our attention on a short (CA)5 microsatellite located in the 5′ untranslated sequence of the glyceraldehyde-3-phosphate dehydrogenase (gpd) gene of P. anserina. Specifically, we investigated whether or not the number of repeat units present in the microsatellite affects the expression of the β-d-glucuronidase (gusA) reporter gene introduced on an autonomously replicating plasmid into fungal protoplasts. The results show that an increase in the number of microsatellite repeat units positively affects reporter gene expression.
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    Expression of a catalytic domain of a Neocallimastix frontalis endoxylanase gene (xyn3) in Kluyveromyces lactis and Penicillium roqueforti (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 208-214 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A cDNA fragment encoding the A catalytic domain of the Neocallimastix frontalis endoxylanase XYN3 was amplified and cloned by the polymerase chain reaction technique. The xyn3A DNA fragment was inserted between the Saccharomyces cerevisiae phosphoglycerate kinase gene promoter and terminator sequences on a multicopy episomal plasmid for Kluyveromyces lactis. The XYN3A domain was successfully expressed in K. lactis and functional endoxylanase was secreted by the yeast cells with the K. lactis killer toxin secretion signal. The XYN3A domain was also expressed in a strain of Penicillium roqueforti as a fusion protein (ShBLE::XYN3A) of the phleomycin-resistance gene product and the endoxylanase. Active endoxylanase was efficiently secreted from the fungal cells with the Trichoderma viride cellobiohydrolase (CBH1) secretion signal and processed by a related KEX2 endoprotease of the secretion pathway. Several differently glycosylated forms of the recombinant enzymes were secreted by the yeast and the filamentous fungus.
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    An acetylxylan esterase and a xylanase expressed from genes cloned from the ruminal fungus Neocallimastix patriciarum act synergistically to degrade acetylated xylans (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 221-225 
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    Notes: Abstract A Neocallimastix patriciarum acetylxylan esterase (BnaA) was expressed from the cloned gene in Escherichia coli. Purified recombinant BnaA efficiently released acetate from soluble acetylated birchwood xylan (ABX), with a specific activity of 76 U mg−1. In contrast, release of acetate was very inefficient from the insoluble substrates, spear grass and delignified spear grass. Addition of a recombinant xylanase, XynA, also expressed from a cloned N. patriciarum gene, had no effect on the release of acetate from ABX. However, the combination of recombinant BnaA and XynA released more acetate from spear grass and delignified spear grass than did BnaA alone. Significantly more reducing sugar was also released from all three substrates by the combination of recombinant XynA and BnaA than by XynA alone. Thus the extent of digestion of acetylated xylans by XynA appears to be limited by the acetylation. In this system BnaA does not appear to increase the rate of cleavage of insoluble substrates by XynA, but probably allows the release of shorter xylose oligomers from already solubilised acetylated xylan polymers.
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    A polymerase chain reaction-based test for the identification of Trichoderma harzianum biotypes 2 and 4, responsible for the worldwide green mold epidemic in cultivated Agaricus bisporus (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 246-250 
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    ISSN: 1432-0614
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We describe a polymerase chain reaction (PCR)-based test that is specific for the pathogenic European biotype 2 (Th2) and North American biotype 4 (Th4) of Trichoderma harzianum, responsible for the green mold epidemic in the cultivated mushroom, Agaricus bisporus. A PCR primer pair was designed that targets a 444-bp arbitrary sequence in the genome of Th4. The primers also amplified the same product with Th2, but showed no reactivity with other biotypes of T. harzianum, several biocontrol Trichoderma, or with 31 other genera and species of fungi. The PCR-based test should have application in disease management programs, and in the evaluation of biocontrol Trichoderma for potential pathogenicity on mushrooms.
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    Biodegradation of methyl violet by Pseudomonas mendocina MCM B-402 (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 251-254 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pseudomonas mendocina MCM B-402 was found to utilize a triphenylmethane dye, methyl violet as the sole source of carbon when incorporated in synthetic medium. Almost complete decolorization of methyl violet by P. mendocina was observed within 48 h of incubation at ambient temperature (28 ± 2 °C) under aerated culture conditions, when the bacteria were inoculated into Davis Mingioli's synthetic medium at a concentration of 100 mg/l medium. Methyl violet was mineralized to CO2 through three unknown intermediate metabolites and phenol. The decolorization of the dye involved demethylation.
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    Properties of free and immobilised lipase from Burkholderia cepacia in organic media (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 276-280 
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The purified lipase from Burkholderia cepacia was immobilised on a porous polypropylene support and its biocatalytic properties were compared with those of the free enzyme in organic media. For both lipase preparations, the rate of p-nitrophenyl ester hydrolysis in n-heptane was not restricted by mass transfer limitations. The immobilisation changed neither the temperature at which the reaction rate was maximal, nor the activation energy of the reaction. The enzyme stability was slightly decreased (1.3-fold) upon immobilisation. Moreover, the immobilised enzyme displayed fewer variations of activity with fatty acid chain length. Interestingly, for all the different p-nitrophenyl esters used, the immobilised enzyme was more active (from 5.8- to 18.9-fold) than the free enzyme. Therefore, it would be very useful to use B. cepacia lipase immobilised onto porous polypropylene for applications in organic media, as it displayed high activities on a larger range of substrates.
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    Inhibiting sulfate-reducing bacteria in biofilms on steel with antimicrobial peptides generated in situ (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 267-275 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In batch and continuous fermentations, the reduction in corrosion of SAE 1018 mild steel and 304 stainless steel caused by inhibition of the reference sulfate-reducing bacterium (SRB) Desulfovibrio vulgaris by a protective, antimicrobial-producing Bacillus brevis biofilm was investigated. The presence of D. vulgaris produced a thick black precipitate on mild steel and a higher corrosion rate in batch cultures than that seen in a mono-culture of non-antimicrobial-producing Pseudomonas fragi K upon the addition of SRB to the aerobic P. fragi K biofilm. In continuous reactors, the polarization resistance R p decreased for stainless steel and increased for mild steel upon the addition of SRB to a P. fragi K biofilm. Addition of either 200 μg/ml ampicillin, chloramphenicol, or ammonium molybdate to batch and continuous reactors after SRB had colonized the metal was ineffective in killing SRB, as inferred from the lack of change in both R p and the impedance spectra. However, when ampicillin was added prior to SRB colonization, the growth of SRB was completely inhibited on stainless steel in continuous reactors. Prior addition of ampicillin was only able to delay the growth of SRB on mild steel in continuous reactors. External addition of the purified peptide antimicrobial agent gramicidin S prior to the addition of SRB also inhibited the growth of SRB on stainless steel in continuous reactors, and the SRB were also inhibited on stainless steel in both batch and continuous reactors by producing gramicidin S in situ in a protective biofilm when the gramicidin-S-overproducing strain Bacillus brevis 18 was used.
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    Production of (R)-3-pentyn-2-ol through stereoinversion of racemic 3-pentyn-2-ol by Nocardia fusca AKU 2123 (1999)
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    Applied microbiology and biotechnology 52 (1999), S. 327-331 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Wet cells of Nocardia fusca AKU 2123 are good catalysts for the production of (R)-3-pentyn-2-ol (PYOH) from (RS)-PYOH through a stereoinversion reaction. Under optimal conditions (350 mM potassium phosphate buffer, pH 8.0, 30% (w/v) wet cells, 0.12% NADPH, 10% glucose, and 30 U/ml glucose dehydrogenase) (R)-PYOH of high optical purity (98.7% e.e.) was produced from 2% (v/v) (RS)-PYOH with a yield of 70.4% by 140 h incubation.
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    Biosynthesis of gibberellins in Gibberella fujikuroi: biomolecular aspects (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 298-310 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Gibberellins (GAs) are a large family of isoprenoid plant hormones, some of which are bioactive growth regulators, controlling seed germination, stem elongation, and flowering. The rice pathogen Gibberella fujikuroi (mating population C) is able to produce large amounts of GAs, especially the bioactive compounds gibberellic acid (GA3) and its precursors, GA4 and GA7. The main steps of the biosynthetic pathway have long been established from the identification of intermediates in wild-type G. fujikuroi and mutant strains. However, the genetics of the fungus have been rather under-developed, and molecular genetic studies of the GA pathway started just recently. The progress in researching GA biosynthesis in the last 2 years resulted primarily from development of the molecular tools, e.g. transformation systems for the fungus, and cloning the genes encoding GA biosynthesis enzymes, such as the bifunctional ent-copalyl diphosphate/kaurene synthase and several cytochrome P450 monooxygenases. The availability of these genes opened new horizons both for detailed study of the pathway and the regulation mechanisms at the molecular level, and for modern strain improvement programs. This review gives a short overview of the well-known physiological and biochemical studies and concentrates mainly on the new molecular genetic data from GA research, including new information on the regulation of GA biosynthesis.
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    URL: http://dx.doi.org/10.1007/s002530051524
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    Yeast cells as tools for target-oriented screening (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 311-320 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Information about biomolecular interaction networks is crucial for understanding cellular functions and the development of disease processes. Many diseases are known to be based on aberrations of DNA sequences encoding proteins with key functions in the cellular metabolism. Alterations in the respective proteins often lead to disturbances in biomolecular interactions caused by unbalanced stoichiometries, and thus result in alterations of molecule fluxes, cell architecture and signalling pathways. Drug discovery programmes have been designed to find promising chemical lead structures with the help of target-oriented bioassay systems. These are, in most cases, based upon the interaction of small molecules to specific macromolecular targets in vivo or in vitro, as exemplified by enzyme assays or small-ligand-based receptor systems. In addition, interactions between large biomolecules, such as proteins or nucleic acids, offer a huge arsenal of potential drug targets that can be addressed by small chemical compounds. This latter approach is gaining considerable attention because many potential target structures are becoming available through genomic research. Funnelling these new targets into high-throughput screening programs represents a major challenge for today's pharmaceutical research. An important outcome of the ongoing genome projects is the fact that the basic cellular structures, pathways and signalling principles show a high degree of conservation. Model organisms that are easily approachable by genetic, biochemical and physiological means can thus play an important role in the design of target-oriented screening systems. They offer the possibility to express individual proteins, nucleic acids or even more complex aggregates of biomolecules such as protein-interaction networks or transcription-initiation complexes, which can be addressed by small effector molecules in vivo. Combining these targets with biological signalling systems is an attractive way of creating robust cellular assay systems.
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    URL: http://dx.doi.org/10.1007/s002530051525
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    Improved process for production of recombinant yeast-derived monomeric human G-CSF (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 338-344 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The human granulocyte colony-stimulating factor (hG-CSF) was efficiently secreted at high levels in fed-batch cultures of recombinant Saccharomyces cerevisiae. However, the secreted recombinant hG-CSF (rhG-CSF) was shown to exist as large multimers in the culture broth due to strong hydrophobic interaction. It was hardly monomerized even by urea at high concentration. This multimer has been reported to diminish specific receptor-binding activity of hG-CSF and causes undesirable problems in the downstream process. When the rhG-CSF was secreted to extracellular broth in the presence of a non-ionic surfactant (Tween 80) in the culture media, the multimerization of the secreted rhG-CSF was efficiently prevented in the fed-batch cultures. Also, the monomer fraction and secretion efficiency of rhG-CSF were significantly increased at the higher culture pH (6.5). Without using any denaturing agents, the secreted rhG-CSF monomer was easily purified with high recovery yield and purity via a simple purification process under acidic conditions, consisting of diafiltration, cation exchange, and gel filtration chromatography. A lyophilization process devoid of intermonomer aggregation was also designed using effective stabilizing agents.
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    URL: http://dx.doi.org/10.1007/s002530051529
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    An integrated strategy for the process development of a recombinant antibody-cytokine fusion protein expressed in BHK cells (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 345-353 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Recombinant fusion proteins offer important new therapeutic approaches for the future. This report describes the use of three different genetic strategies (i.e. “mono-”, “bi-” and “tri-cistronic” vectors) to achieve stable secretion from BHK cells of a glycosylated antibody-cytokine fusion protein designed for use in anti-tumour therapy. It describes selection of a robust and effective production cell line based on stability of secretion of the product, quality of mRNA and protein products and performance in in vitro bioassays for potency. The data obtained at this stage were utilised in the selection of a suitable candidate production cell line. The relative productivity and general performance of the cells in stirred tank and fixed bed culture systems indicated that a variety of cell culture technologies provided robust tools for production of a highly selected cell clone. Consistency of the product glycosylation was determined by analysis of released oligosaccharides using matrix-assisted laser desorption ionisation – time of flight mass spectrometry and high-performance anion exchange chromatography. These investigations showed consistent expression of three glycoforms of the fusion protein which varied in their relative proportions in different culture systems and at different time points in a fixed bed reactor with continuous perfusion. In conclusion, this study dealt with a range of important scientific and technical issues which are essential for regulatory approval and commercial success of a recombinant protein and elucidates some useful markers for process development for similar recombinant biologicals.
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    URL: http://dx.doi.org/10.1007/s002530051530
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    Comparative assessment of chelated spent mushroom substrates as casing material for the production of Agaricus bisporus (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 366-372 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Spent mushroom substrate (SMS) leached with water or treated with chelating agents to remove metal cations, pasteurised to remove any harmful micro-organisms and mixed with peat has potential as a casing material for mushroom production. The microbial and chemical changes in SMS after treatment with citric acid, ethylene diaminetetraacetic acid (EDTA) and water were compared; treatment with the chelating agents resulted in lower ash content, conductivity and minerals, higher fibre fractions, carbon, hydrogen and nitrogen. The microbial and chemical changes in the materials after treatment with the two chelators and water were compared. Blending peat with the heat-treated materials at a ratio of 1:1 resulted in improved physical properties. The casings prepared from the test materials and the control, consisting of 100% peat, were compared after neutralising with lime for their productivity in a mushroom yield trial. As expected, the compost bags cased with the control were the most productive compared to the other casings. Of the three treated materials, casing prepared from SMS treated with EDTA blended with peat was the most productive. Dry matter of harvested mushrooms from chelated-SMS casings was significantly higher than the control casing. Comparison of the main components of peat and chelated SMS revealed that the major differences were in the proportions of ash, lipid, lignin and fibre fractions. The stability of some of these components, when complexed with metal cations present in lime may play an important role in determining the composition of the cell wall in fruiting bodies leading to high dry matter content.
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    URL: http://dx.doi.org/10.1007/s002530051533
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    Substrate specificity and stereospecificity of limonene-1,2-epoxide hydrolase from Rhodococcus erythropolis DCL14; an enzyme showing sequential and enantioconvergent substrate conversion (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 380-385 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Limonene-1,2-epoxide hydrolase (LEH) from Rhodococcus erythropolis DCL14, an enzyme involved in the limonene degradation pathway of this microlorganism, has a narrow substrate specificity. Of the compounds tested, the natural substrate, limonene-1,2-epoxide, and several alicyclic and 2-methyl-1,2-epoxides (e.g. 1-methylcyclohexene oxide and indene oxide), were substrates for the enzyme. When LEH was incubated with a diastereomeric mixture of limonene-1,2-epoxide, the sequential hydrolysis of first the (1R,2S)- and then the (1S,2R)-isomer was observed. The hydrolysis of (4R)- and (4S)-limonene-1,2-epoxide resulted in, respectively, (1S,2S,4R)- and (1R,2R,4S)-limonene-1,2-diol as the sole product with a diastereomeric excess of over 98%. With all other substrates, LEH showed moderate to low enantioselectivities (E ratios between 34 and 3).
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    Enhanced production of penicillin V acylase from Streptomyces lavendulae (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 81-84 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract At 28 °C, Streptomyces lavendulae produced high levels of penicillin V acylase (178 IU/l of culture) when grown on skim milk as the sole nutrient source for 275 h. The enzyme showed catabolite repression by glucose and was produced in the stationary phase of growth. Penicillin V was a good inducer of penicillin V acylase formation, while phenoxyacetic acid, the side-chain moiety of penicillin V, did not alter enzyme production significantly. The enzyme was stable between pH 6 and 11 and at temperatures from 20 °C to 55 °C. This extracellular enzyme was able to hydrolyse natural penicillins and unable to hydrolyse penicillin G.
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    Metabolism of 2,4,6-trinitrotoluene by the white-rot fungus Bjerkandera adusta DSM 3375 depends on cytochrome P-450 (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 75-80 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Degradation of 2,4,6-trinitrotoluene (TNT) by the white-rot fungus Bjerkandera adusta DSM 3375 was studied in relation to extracellular ligninolytic activities. The Mn(II)-dependent peroxidase, the only ligninolytic enzyme detectable, reached a maximum activity of 600 ± 159 U/l after incubation in mineral medium with a sufficient nitrogen source. In contrast, the highest extent of [14C]TNT mineralization was detected in malt extract broth, so that the ability of B. adusta to mineralize TNT did not parallel ligninolytic activity. The microsomal fraction of cells grown in the presence of TNT was found to contain 11 pmol cytochrome P-450/mg protein. In cells grown without TNT, no microsomal cytochrome P-450 could be found. Instead, 14 pmol P-450/mg protein was present in the cytosolic fraction of these cells. Cytochrome P-450 apparently affected the TNT metabolism, as shown by inhibitory studies. Addition of the cytochrome P-450 inhibitor piperonyl butoxide diminished the 14CO2 release from 21% to 0.9%, as determined after 23 days of incubation, while 1-aminobenzotriazole and metyrapone decreased the mineralization to 8.6% and 6.3% respectively. Mass-balance analysis of TNT degradation in liquid cultures revealed that, by inhibition of cytochrome P-450, the TNT-derived radioactivity associated with biomass and with polar, water-soluble metabolites decreased from 93.9% to 15.0% and the fraction of radiolabelled metabolites extractable with organic solvents fell to 92.6%. The TNT metabolites of this fraction were identified as aminodinitrotoluenes, indicating that this initial transformation product of TNT may function as a substrate for cytochrome-P-450-dependent reactions in B. adusta.
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    Bioavailability of polycyclic aromatic hydrocarbons and formation of humic acid-like residues during bacterial PAH degradation (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 85-91 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The degradation of single polycyclic aromatic hydrocarbons (PAHs: naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) and a mixture of all seven PAHs by a bacterial culture enriched from contaminated soil resulted in the formation of a dark-coloured residual fraction of dissolved (DOM) and particulate organic matter (POM). This fraction was highly resistant to bacterial degradation. Analysis of the DOM revealed a molecular-size-distribution similar to that of natural humic acids. A complete degradation of PAHs was apparently prevented by an irreversible incorporation of about 10% of the carbon from single PAHs or 20% of the carbon from the mixture of seven PAHs into the DOM- and POM- fraction. Some metabolites excreted during bacterial PAH-degradation were identified as known precursors for humification.
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    Oxygen-dependent xylitol metabolism in Pichia stipitis (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 92-97 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pichia stipitis CBS 6054 was cultivated in chemostat cultures under aerobic and oxygen-limited conditions with xylitol alone, a mixture of xylitol and glucose and a mixture of xylitol and xylose. Xylitol metabolism was strictly respiratory and no ethanol was formed. Simultaneous feeding of xylitol and glucose and xylitol and xylose to oxygen-limited xylitol-pregrown cells resulted in ethanol formation. In vitro both pyruvate decarboxylase activity and alcohol dehydrogenase activity were present in cells metabolising xylitol under oxygen-limited conditions; however, this did not result in ethanol formation. Glucose, xylose and xylitol utilisation, respectively, were compared under anaerobic conditions with regard to growth rate, carbon source and oxygenation level during pre-cultivation. Irrespective of pre-growth conditions, xylitol was not metabolised under anaerobic conditions, whereas ethanol was formed from both xylose and glucose. Anaerobic xylose utilisation required induction of a xylose-utilising metabolic pathway during pre-cultivation.
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    URL: http://dx.doi.org/10.1007/s002530051620
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    Functionality of biphenyl 2,3-dioxygenase components in naphthalene 1,2-dioxygenase (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 592-597 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Naphthalene 1,2-dioxygenase (Nap dox) and biphenyl 2,3-dioxygenase (Bph dox) are related enzymes that have differentiated during evolution as their specificity has changed. Although their component arrangement is similar, the structure of each component has been modified quite extensively. The purpose of this work was to determine the catalytic capacity of purified Nap dox toward chlorobiphenyls and to investigate the functionality of Bph dox components in the Nap dox system. Both enzyme systems were purified by affinity chromatography as histidine-tagged fused proteins. Data show for the first time that Nap dox can catalyze the oxygenation of all three monochlorobiphenyl isomers, but it is unable to hydroxylate 2,5-, 2,2′-, 3,3′-, 4,4′-di- and 2,2′,5,5′-tetrachlorobiphenyl. The rates of cytochrome c reduction by the ferredoxin components of the two enzymes were identical when the Bph dox reductase component was used in the assay, showing an efficient electron transfer between the Bph dox reductase component and the Nap dox ferredoxin. However, when the Bph dox ferredoxin was used to reconstitute a hybrid Nap dox, the enzyme was only 22% as active as the parental enzyme. These data are discussed in terms of the potential use of Nap dox for the development of enhanced chlorobiphenyl-degrading dioxygenases.
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    Substrate specificities of the chloromuconate cycloisomerases from Pseudomonas sp. B13, Ralstonia eutropha JMP134 and Pseudomonas sp. P51 (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 598-605 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The chloromuconate cycloisomerase of Pseudomonas sp. B13 was purified from 3-chlorobenzoate-grown wild-type cells while the chloromuconate cycloisomerases of Ralstonia eutropha JMP134 (pJP4) and Pseudomonas sp. P51 (pP51) were purified from Escherichia coli strains expressing the corresponding gene. Kinetic studies were performed with various chloro-, fluoro-, and methylsubstituted cis,cis-muconates. 2,4-Dichloro-cis,cis-muconate proved to be the best substrate for all three chloromuconate cycloisomerases. Of the three enzymes, TfdD of Ralstonia eutropha JMP134 (pJP4) was most specific, since its specificity constant for 2,4-dichloro-cis,cis-muconate was the highest, while the constants for cis,cis-muconate, 2-chloro- and 2,5-dichloro-cis,cis-muconate were especially poor. The sequence of ClcB of the 3-chlorobenzoate-utilizing strain Pseudomonas sp. B13 was determined and turned out to be identical to that of the corresponding enzyme of pAC27 (though slightly different from the published sequences). Corresponding to 2-chloro-cis,cis-muconate being a major metabolite of 3-chlorobenzoate degradation, the k cat/K m with 2-chloro-cis,cis-muconate was relatively high, while that with the still preferred substrate 2,4-dichloro-cis,cis-muconate was relatively low. This enzyme was thus the least specific and the least active among the three compared enzymes. TcbD of Pseudomonas sp. P51 (pP51) took an intermediate position with respect to both the degree of specificity and the activity with the preferred substrate.
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    Purification and mode of action of two different arabinoxylan arabinofuranohydrolases from Bifidobacterium adolescentis DSM 20083 (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 606-613 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two novel arabinofuranohydrolases (AXH-d3 and AXH-m23) were purified from Bifidobacterium adolescentis DSM 20083. Both enzymes were induced upon growth of Bi. adolescentis on xylose and arabinoxylan-derived oligosaccharides. They were only active with arabinoxylans and therefore denoted as arabinoxylan arabinofuranohydrolases. Their optimal activity was at pH 6 and 30–40 °C. They were very specific in their mode of action and were clearly different from AXH-m from Aspergillus awamori. AXH-m23 released only arabinosyl groups, which were linked to the C-2 or C-3 position of singly substituted xylose residues in arabinoxylan oligomers. AXH-d3 hydrolysed C-3-linked arabinofuranosyl residues of doubly substituted xylopyranosyl residues of arabinoxylans and arab- inoxylan-derived oligosaccharides. No activity was observed with C-2-linked arabinofuranosyl residues of these doubly substituted xylopyranosyl residues, or against C-2- and C-3-linked arabinofuranosyl residues of singly substituted xylopyranosyl residues. The combination of AXH-d3 and AXH-m showed low debranching activity with highly substituted glucurono-arabinoxylans. However, arabinoxylan from wheat flour was debranched almost completely.
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    Development of a bioconversion process for production of cis-1S,2R-indandiol from indene by recombinant Escherichia coli constructs (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 614-620 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Recombinant Escherichia coli cells expressing the toluene dioxygenase (TDO) genes from Pseudomonas putida convert indene to cis-1S,2R-indandiol, a potentially important intermediate for the chemical synthesis of the HIV-1 protease inhibitor, Crixivan. A bioconversion process was developed through optimization of medium composition and reaction conditions at the shake-flask and 23-l fermentor scales. A cis-1,2-indandiol productivity of approx. 1000 mg/l was achieved with construct TDO123, which represents a 50-fold increase over the initial titer. Varying the bioconversion conditions did not change the enantiomeric excess (e.e.) for the 1S,2R enantiomer from about 30%, suggesting that toluene dioxygenase intrinsically converts indene to 1S,2R- and 1R,2S-indandiols at a ratio of 2:1. Further inclusion of the Pseudomonas dehydrogenase gene in construct D160-1 led to the production of chirally pure cis-1S,2R-indandiol (e.e. 〉 99%) as a result of the selective degradation of the 1R,2S enantiomer, with the overall yield (650 mg/l) proportionally reduced. A single stage process was developed for D160-1 and scaled up to the 23-l fermentor, achieving a cis-1S,2R-indandiol titer of 1200 mg/l.
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    Construction of a flocculent Saccharomyces cerevisiae fermenting lactose (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 621-626 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A flocculent Saccharomyces cerevisiae strain with the ability to express both the LAC4 (coding for β-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus was constructed. This recombinant strain is not only able to grow on lactose, but it can also ferment this substrate. To our knowledge this is the first time that a recombinant S. cervisiae has been found to ferment lactose in a way comparable to that of the existing lactose-fermenting yeast strains. Moreover, the flocculating capacity of the strain used in this work gives the process several advantages. On the one hand, it allows for operation in a continuous mode at high cell concentration, thus increasing the system's overall productivity; on the other hand, the biomass concentration in the effluent is reduced, thus decreasing product separation/purification costs.
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    High-level expression of a recombinant protein in Klebsiella planticola owing to induced secretion into the culture medium (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 627-632 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Tn5-based transposon Tn5-KIL3 (Miksch et al. 1997c) bearing the kil gene of the ColE1 plasmid of Escherichia coli, which mediates controlled export of periplasmic proteins into the culture medium, was stably integrated into the chromosome of Klebsiella planticola with high transposition frequency. A Bacillus hybrid β-glucanase located on an RSF1010-derived plasmid was mobilized from E.coli to K. planticola and used as a reporter protein to select strains with high expression and secretion competence. During fermentation experiments it was shown that the production of β-glucanase in K. planticola was improved to an unexpectedly high level when the enzyme was secreted into the medium. Due to the stationary-phase promoter used for the expression of the kil gene the secretion of β-glucanase into the medium started at the transition from the exponential to the stationary phase, as in E. coli, and the fraction of secreted protein reached 90%. The results showed that K. planticola may represent an interesting organism for the production of heterologous proteins.
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    The role of the alternative respiratory pathway in the stimulation of cephalosporin C formation by soybean oil in Acremonium chrysogenum (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 633-638 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Addition of soybean oil to Acremonium chrysogenum cultures growing on sugars doubled the specific production of cephalosporin C during the idiophase of growth. While the addition of soybean oil had no effect on the total rate of respiration, the respiration that proceeded via the alternative, cyanide-insensitive pathway exhibited a more than twofold increase. Addition of soybean oil also stimulated the formation of isocitrate lyase activities. Inhibition of oxidative metabolism of one of the products of isocitrate lyase (succinate) by thenoyltrifluoroacetone completely inhibited the alternative respiratory pathway. The role of soybean-oil-stimulated alternative respiration in the stimulation of cephalosporin C production and the role of isocitrate lyase are discussed.
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    Effects of culture conditions on β-poly(l-malate) production by Physarum polycephalum (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 647-652 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Culture conditions for the fermentative production of β-poly(l-malate) (PMLA) by microplasmodia of Physarum polycephalum were investigated and optimized. Optimal production was achieved in the presence of CaCO3. For 1.5% (w/v) d-glucose, 1% bactotryptone and 1% CaCO3, a maximum of 1.7 g PMLA/l was secreted in 3 days. For 4.5% glucose and otherwise the same conditions, 2.7 g PMLA/l was produced in 6 days. The contribution of carbonate was inhibited by avidin. PMLA and biomass production were not strictly coupled: PMLA was also synthesized at the beginning of the stationary phase. At pH 5.5 PMLA production was twice that at pH 4.0, while biomass was not changed. Optimal temperatures were 24–28 °C.
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    Polyphosphate formation by Acinetobacter johnsonii 210A: effect of cellular energy status and phosphate-specific transport system (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 639-646 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In acetate-limited chemostat cultures of Acinetobacter johnsonii 210A at a dilution rate of 0.1 h−1 the polyphosphate content of the cells increased from 13% to 24% of the biomass dry weight by glucose (100 mM), which was only oxidized to gluconic acid. At this dilution rate, only about 17% of the energy from glucose oxidation was calculated to be used for polyphosphate synthesis, the remaining 83% being used for biomass formation. Suspensions of non-growing, phosphate-deficient cells had a six- to tenfold increased uptake rate of phosphate and accumulated polyphosphate aerobically up to 53% of the biomass dry weight when supplied with only orthophosphate and Mg2+. The initial polyphosphate synthesis rate was 98 ± 17 nmol phosphate min−1 mg protein−1. Intracellular poly-β-hydroxybutyrate and lipids served as energy sources for the active uptake of phosphate and its subsequent sequestration to polyphosphate. The H+-ATPase inhibitor N,N′-dicyclohexylcarbodiimide caused low ATP levels and a severe inhibition of polyphosphate formation, suggesting the involvement of polyphosphate kinase in polyphosphate synthesis. It is concluded that, in A. johnsonii 210A, (i) polyphosphate is accumulated as the energy supply is in excess of that required for biosynthesis, (ii) not only intracellular poly-β-hydroxybutyrate but also neutral lipids can serve as an energy source for polyphosphate-kinase-mediated polyphosphate formation, (iii) phosphate-deficient cells may accumulate as much polyphosphate as activated sludges and recombinants of Escherichia coli designed for polyphosphate accumulation.
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    An image analysis method for determination of spatial colonization patterns of bacteria in plant rhizosphere (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 653-658 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A method that allows the rapid visualization of bacterial spatial colonization patterns on roots for the determination of general colonization trends was developed. This method, which analyzes images of roots, and bioluminescence-enhanced images of bacterial colonization patterns on these roots, was used to study the colonization patterns of seed-applied Enterobacter cloacae strain E6 on 3-day-old cucumber plants. Conventional dilution-plating methods indicated that E6 colonized cucumber tap roots in high populations and that these populations significantly decreased as the distance from the seed increased. In addition to confirming these observations, image analysis indicated that colonization by E6 significantly decreased on lateral roots as the distance increased horizontally away from the tap root, and that this bacterium did not evenly cover the most densely colonized regions of the cucumber root system. Results from these experiments indicate that the majority of E6 populations on cucumber roots after seed application are limited to the upper regions of the tap root and that E6 does not effectively colonize other regions of the root system.
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    Characterization of Lactobacillus collinoides response to heat, acid and ethanol treatments (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 659-663 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Tolerance to stress and cross-protection in Lactobacillus collinoides were examined after exposure to ethanol, acid or heat shock. Ethanol and heat-adapted cells demonstrate induced homologous␣tolerance and cross-resistance to acid stress. No cross-protection of acid-adapted cells against ethanol and heat stresses was observed. Heat was the only pretreatment leading to cross-protection against the two other stresses. Whole-cell protein extract analysis revealed that each treatment induced a battery of stress proteins; the synthesis of some of these polypeptides being induced by more than one condition. The greatest overlap was observed between ethanol and heat treatments. Ten proteins were found to be common to these stresses.
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    Effect of temperature and pH on growth and product formation of Lactococcus lactis ssp. lactis ATCC 19435 growing on maltose (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 669-672 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Lactococcus lactis ssp. lactis ATCC 19435 is known to produce mixed acids when grown on maltose. A change in fermentation conditions only, elevated temperatures (up to 37 °C) and reduced pH values (down to 5.0) resulted in a shift towards homolactic product formation. This was accompanied by decreased growth rate and cell yield. The results are discussed in terms of redox balance and maintenance, and the regulation of lactate dehydrogenase and pyruvate formate-lyase.
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    An electrochemical method for the measurements of substrate-oxidizing activity of acetic acid bacteria using a carbon-paste electrode modified with immobilized bacteria (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 664-668 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In order to measure the substrate-oxidizing activity of intact cells of Acetobacter pasteurianus no. 2, a given amount of the bacterial cells was immobilized on a carbon-paste electrode, and the current at the electrode was measured in a buffer solution. When Fe(CN)3− 6 was added to the buffer solution, an anodic current was observed at 0.5 V (against Ag/AgCl). Further, when ethanol was added to the solution, the current started to increase to reach a steady-state within 3 min. The electrode had a good response to acetaldehyde and lactic acid as well as ethanol. Culture conditions affected the current response to various substances; the response of the electrode modified with the cells grown in static culture was much higher than that of the electrode with the cells grown in shaking culture, and the electrode with ethanol-grown cells had a high response to ethanol and acetaldehyde compared with that of the electrode with glucose-grown cells. The increase in the amount of the current after the addition of ethanol (ΔI EtOH) was linearly proportional to the total number of immobilized cells per electrode in the range 1.0 × 104–1.0 × 108 cells. The ΔI EtOH values were measured with the electrode prepared with a fixed volume of the cell suspensions taken from the culture at 6-h intervals; the dependence of the ΔI EtOH value on time agreed well with the cell growth measured by colony counting and turbidity in the lag and logarithmic phase. After the logarithmic phase, the value of ΔI EtOH sharply decreased, resembling to the growth measured by colony counting, rather than by turbidity.
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    High-density Escherichia coli cultures for continuous l(−)-carnitine production (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 760-764 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The use of a biological procedure for l-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction system. Continuous l-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst. This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g l-carnitine l−1 h−1). This process showed its feasibility for industrial l-carnitine production. In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this particular method of cultivation was used.
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    Tetrachloroethene dechlorination kinetics by Dehalospirillum multivorans immobilized in upflow anaerobic sludge blanket reactors (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 694-699 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Tetrachloroethene (C2Cl4) dechlorination kinetics in upflow anaerobic sludge blanket (UASB) reactors was determined after introducing de novo activities into the granular sludge. These activities were introduced by immobilizing Dehalospirillum multivorans in a test reactor containing unsterile granular sludge, and in a reference reactor, R1, containing sterile granular sludge. A second reference reactor, R2, contained only unsterile granular sludge and served as a control. The kinetic experiments were performed by pulsing the reactors with C2Cl4 in a recirculating batch mode. Formate and acetate were added as electron donor and carbon source. Both reactors inoculated with D. multivorans dechlorinated C2Cl4 to an equimolar amount of C2H2Cl2 with only traces of C2HCl3 in the effluent. In the control reactor, C2HCl3 accumulated before C2H2Cl2 was produced. A computer simulation program (AQUASIM) was used to estimate the kinetic parameters. The half-saturation constants (K s) for C2Cl4 and C2HCl3 were almost equal in the reactors containing D.␣multivorans (17 μM and 18 μM for C2Cl4; 26 μM and 28 μM for C2HCl3), indicating no influence of sludge bacteria on the affinity of D. multivorans for C2Cl4 and C2HCl3. The maximum dechlorination rates (k m X B) were about twice as high in the reactor containing D.␣multivorans immobilized in sterile sludge (11 mmol C2Cl4 l sludge−1 day−1 and 27 mmol C2HCl3 l sludge−1 day−1) than in the test reactor (4.4 mmol C2Cl4 l sludge−1 day−1 and 15 mmol C2HCl3 l sludge−1 day−1). Compared to other C2Cl4-degrading systems, the dechlorination rates of the inoculated reactors and their affinities for C2Cl4 and C2HCl3 were high. Therefore, introduction of de novo activity is promising for the use of anaerobic reactors to bioremediate C2Cl4-polluted water.
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    Artificial redox coenzymes: biomimetic analogues of NAD+ (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 703-710 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A range of biomimetic analogues of the nicotinamide nucleotide coenzymes NAD(P)(H) have been developed based on the structure of a triazine dye template. These biomimetic redox coenzymes are relatively straightforward and inexpensive to synthesise and display NAD+-like activity with different dehydrogenases, despite their apparently minimal structural similarity to the native coenzyme NAD+. Horse liver alcohol dehydrogenase oxidises butan-1-ol, using the most active biomimetic coenzyme (Nap 1), with a k cat value an order of magnitude lower and a K m for the coenzyme two orders of magnitude higher than those using native NAD+. The enzymatically reduced biomimetic coenzymes may be reoxidised by phenazine methosulfate. We believe that these coenzymes may find applications in biotransformations and biosensors, and in the development of biomimetic catalysts where the redox enzyme itself is replaced by a synthetic binding site.
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    Quantification of bacterial polyhydroxyalkanoic acids by Nile red staining (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 765-772 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The fluorescence properties of one chemically and seven biologically produced polyhydroxyalkanoic acids were investigated as film castings and in living cells respectively after staining with Nile red. All these polyesters show a similar fluorescence behaviour, revealing a clear fluorescence maximum at an excitation wavelength between 540 nm and 560 nm and an emission wavelength between 570 nm and 605 nm. This could be shown by the use of two-dimensional fluorescence spectroscopy and flow cytometry. The examination of native poly(3-hydroxybutyric acid), poly(3HB), granules isolated from cells of Ralstonia eutropha H16 showed that the addition of 6.0 μg Nile red is necessary for total staining of 1.0 mg granules. The fluorescence intensity at an excitation wavelength of 550 nm and an emission wavelength of 600 nm showed high correlation to the poly(3HB) concentration of grana suspensions at different grana concentrations. These results and the staining of cell suspensions during cultivation experiments revealed that Nile red has a high potential for the quantitative determination of hydrophobic bacterial polyhydroxyalkanoic acids.
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    Improvement of mechanical and biological properties of freeze-dried denitrifying alginate beads by using starch as a filler and carbon source (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 773-779 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Freeze-dried, alginate-based beads, used for the immobilization of a denitrifying bacterium (Pseudomonas sp.), were filled with different concentrations (10%, 20%, 30% and 40%, w/w) of granular starch. The beads were incubated under denitrifying conditions in laboratory-scale, flow-through columns and monitored for changes in their physical and denitrifying properties. Freeze-dried beads containing high concentrations of starch were found to have better mechanical and denitrifying properties than beads containing low concentrations of this filler. Nitrate removal by the beads was found to be correlated with their starch content. Nitrite accumulation, as a result of incomplete denitrification, increased with the decrease in starch content of the beads. Nitrite in the outlet of the columns was measured in all types of beads during the initial phase of incubation but was undetectable, with the exception of beads with the lowest starch content, at later stages of incubation.
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    Isolation and characterization of indene bioconversion genes from Rhodococcus strain I24 (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 786-793 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rhodococcus strain I24 is able to convert indene into indandiol via the actions of at least two dioxygenase systems and a putative monooxygenase system. We have identified a cosmid clone from I24 genomic DNA that is able to confer the ability to convert indene to indandiol upon Rhodococcus erythropolis SQ1, a strain that normally can not convert or metabolize indene. HPLC analysis reveals that the transformed SQ1 strain produces cis-(1R,2S)-indandiol, suggesting that the cosmid clone encodes a naphthalene-type dioxygenase. DNA sequence analysis of a portion of this clone confirmed the presence of genes for the dioxygenase as well as genes encoding a dehydrogenase and putative aldolase. These genes will be useful for manipulating indene bioconversion in Rhodococcus strain I24.
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    Oxygen starvation induces cell death in Candida shehatae fermentations of d-xylose, but not d-glucose (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 780-785 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Candida shehatae cells, cultivated on d-glucose and d-xylose, were subjected to a shift from fully aerobic to anaerobic fermentative conditions. After anaerobic conditions were imposed, growth was limited to approximately one doubling or less as C. shehatae rapidly entered a stationary phase of growth. Following the shift to anoxia, cell viability rapidly declined and the total cell volume declined in the d-xylose fermentations. Moreover, the cell volume distribution shifted to smaller volumes. Cell viability, measured by plate counts, declined nine times faster for d-xylose fermentations than for d-glucose fermentations. Anaerobic growth did not occur on either d-glucose or d-xylose. Selected vitamins and amino acids did not stimulate anaerobic growth in C. shehatae, but did enhance anaerobic growth on d-glucose in S. cerevisiae. The decline in cell viability and lack of anaerobic growth by C. shehatae were attributed to oxygen deficiency and not to ethanol inhibition. The results shed light on why C. shehatae anaerobic fermentations are not currently practical and suggest that research directed towards a biochemical understanding of why C. shehatae can not grow anaerobically will yield significant improvements in ethanol fermentations from d-xylose.
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    Degradation of dioxin-like compounds by microorganisms (1998)
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    Applied microbiology and biotechnology 49 (1998), S. 489-499 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF; PCDD/F, dioxins) have not been commercially produced in bulk amounts, as were polychlorinated biphenyls and other haloaromatic organics. Within the past two decades a lot␣of information has accumulated on the biodegradation of PCDD/F and other dioxin-like compounds because of their toxicity and because of significant environmental concern about many congeners of this class of chemicals. PCDD/F are subjected to reductive dehalogenations leading to less halogenated congeners, which can be attacked efficiently by fungal and bacterial oxidases and dioxygenases. In several cases these compounds can be utilized as carbon and energy sources. Pathways for their enzymatic degradation and the organisation of the corresponding degradative genes have been elucidated. Consequently, biotechnological applications will exploit the degradative potential of such microorganisms for bioremediation of contaminated sites.
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    Energy uncoupling in microbial growth under substrate-sufficient conditions (1998)
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    Applied microbiology and biotechnology 49 (1998), S. 500-505 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract It has been observed that the correlation between ATP and biomass formation is very poor, and the observed growth yield is lowered under substrate-sufficient conditions. This indicates that the excess substrate causes uncoupling between anabolism and catabolism, which leads to the dissipation of non-growth energy. However, a quantitative description of such uncoupling remains elusive. Based on a balanced substrate reaction, a growth-yield model in relation to residual substrate concentration for substrate-sufficient continuous cultures was developed. On the basis of this yield model, a coefficient governing the uncoupling of anabolism and catabolism was defined. A model describing the effect of the residual substrate concentration on this uncoupling coefficient was further proposed. These models agree with experimental data very well. It is clearly shown that, under substrate-sufficient conditions, the variation in growth efficiency is mainly due to energy uncoupling rather than to maintenance energy expenditure.
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    Ethanol production using nuclear petite yeast mutants (1998)
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    Applied microbiology and biotechnology 49 (1998), S. 511-516 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two respiratory-deficient nuclear petites, FY23Δpet191 and FY23Δcox5a, of the yeast Saccharomyces cerevisiae were generated using polymerase-chain-reaction-mediated gene disruption, and their respective ethanol tolerance and productivity assessed and compared to those of the parental grande, FY23WT, and a mitochondrial petite, FY23ρ0. Batch culture studies demonstrated that the parental strain was the most tolerant to exogenously added ethanol with an inhibition constant. K i, of 2.3% (w/v) and a specific rate of ethanol production, q p, of 0.90 g ethanol g dry cells−1 h−1. FY23ρ0 was the most sensitive to ethanol, exhibiting a K i of 1.71% (w/v) and q p of 0.87 g ethanol g dry cells−1 h−1. Analyses of the ethanol tolerance of the nuclear petites demonstrate that functional mitochondria are essential for maintaining tolerance to the toxin with the 100% respiratory-deficient nuclear petite, FY23Δpet191, having a K i of 2.14% (w/v) and the 85% respiratory-deficient FY23Δcox5a, having a K i of 1.94% (w/v). The retention of ethanol tolerance in the nuclear petites as compared to that of FY23ρ0 is mirrored by the ethanol productivities of these nuclear mutants, being respectively 43% and 30% higher than that of the respiratory-sufficient parent strain. This demonstrates that, because of their respiratory deficiency, the nuclear petites are not subject to the Pasteur effect and so exhibit higher rates of fermentation.
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    Fungal pretreatment by Phanerochaete chrysosporium to reduce the inhibition of methanogenesis by dehydroabietic acid (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 538-544 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The white-rot basidiomycete Phanerochaete chrysosporium BKM-F-1767 was tested for its capacity to degrade dehydroabietic acid (DHA). In anaerobic treatment, this molecule is the most recalcitrant member of the resin acid group, which is known to cause operational problems to anaerobic reactors treating pulp and paper industry wastewaters. In this study the effect of DHA on different parameters, such as growth, ligninolytic enzyme activity, extracellular protein production as well as both glycerol and ammonium consumption by the fungus, was determined. Although the above parameters were affected by the addition of DHA, the results show that the fungus could still produce significant titres of ligninolytic enzymes. The fungus removed 47% of the DHA initially present in the static culture, after 10 days of incubation. Anaerobic toxicity assays showed that the treatment of DHA with P. chrysosporium reduced the methanogenesis and acetogenesis inhibition caused by DHA and allowed improved methane production by the anaerobic bacteria.
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    Recombinant bioprocess optimization for heterologous protein production using two-stage, cyclic fed-batch culture (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 531-537 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A two-stage, cyclic fed-batch bioprocess was designed, and its performance evaluated to improve rice α-amylase productivity by the yeast Yarrowia lipolytica SMY2 (MatA, ade1, ura3, xpr2), ATCC 201847, containing a replicative plasmid coding for a rice α-amlyase. Transcription of the recombinant gene is controlled by the XPR2 promoter. The first stage (or growth stage) was operated in the fed-batch mode, and the growth medium, designed to maintain a constant high cell density (i.e., 60 g/l), was fed according to a predetermined and preprogrammed optimal feed rate which, in turn, maintained the specific cell growth rate at an optimal value (i.e., 0.1 h−1). Typically, when the volume in the first stage reached a preset value, a portion of culture broth (i.e., 55%) was transferred to the second stage (or production stage). The remaining cells in the growth stage were then fed with fresh growth medium according to the bioprocess control strategy developed, while induction of α-amylase expression and its production was taking place in the second stage. The second stage was also operated in the fed-batch mode, and the production medium designed to maintain a constant high cell density and high productivity of heterologous protein was fed at a predetermined and preprogrammed rate, which maintained the specific cell growth rate at an optimal level. The volumetric α-amylase productivity achieved (1835 units l−1 h−1) from the two-stage, cyclic fed-batch culture process was twofold higher than that of the fed-batch culture process. The genetic stability of the recombinant strain and the design of optimal media for growth and production stages are also critically important to a successful implementation of the two-stage, cyclic fed-batch process for production of heterologous protein.
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    Laccase from the white-rot fungus Trametes trogii (1998)
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    Applied microbiology and biotechnology 49 (1998), S. 545-551 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The white-rot fungus Trametes trogii excretes a main laccase showing a molecular mass of 70 kDa, acidic isoelectric point and N-terminal sequence homol-ogous to that of several phenol oxidases. The purified enzyme oxidizes a number of phenolic and non-phenolic compounds; recalcitrant molecules may be converted into substrates by introducing, in the correct position, o-␣or p-orienting ring-activating groups.
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    Production of a new DNA vehicle for gene transfer using site-specific recombination (1998)
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    Applied microbiology and biotechnology 49 (1998), S. 560-567 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Supercoiled DNA molecules, minicircles, were produced by in vivo site-specific recombination. They contained exclusively the desired excisable fragment. Recombination was driven by bacteriophage λ integrase from a plasmid substrate containing the attP and attB recombination sites in the same orientation. Conditions for minicircle production within the lysogen Escherichia coli D1210HP were optimised. Up to 1.5 mg minicircles could be produced per litre bacterial culture, and the remaining, unrecombined plasmid comprised less than about 15% of the minicircle produced. However minicircle multimers were also produced, and comprised up to 30% of all minicircles synthesised. The parABCDE′ locus from plasmid RK2 was introduced into the minicircle fragment, resulting in minicircle dimers being reduced to less than 2% of all minicircles. The parA gene encodes a resolvase that catalyses recombination at the multimer resolution site in the parABCDE′ locus. Minicircle multimers were also resolved when parA was introduced downstream from the integrase gene of the λp L transcript in D1210HP together with a multimer resolution site carried by the minicircle fragment.
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    Overexpression of high-molecular-mass nitrile hydratase from Rhodococcus rhodochrous J1 in recombinant Rhodococcus cells (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 568-572 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract High-molecular-mass nitrile hydratase (H-NHase, 530 kDa) is a cobalt-containing enzyme produced by Rhodococcus rhodochrous J1. For efficient production of H-NHase in R. rhodochrous ATCC12674, several plasmids were constructed. The enzyme was produced in the recombinant Rhodococcus cells only in the presence of an upstream region (approximately 4 kb) of the H-NHase gene under the control of the promoter for the amidase-NHase gene cluster from Rhodococcus sp. N-774. Although H-NHase was produced as a soluble protein in the cells, the protein did not show NHase activity. However, when the recombinant R. rhodochrous ATCC12674 cells were cultured in the presence of amide compounds, such as crotonamide and methacrylamide, markedly high NHase activity was detected. Gel-filtration chromatography revealed that the NHases produced by the cells grown in the presence and absence of the amide compounds had a molecular mass of more than 500 kDa and 50–80 kDa respectively. These results suggest that the amide compounds are essential for subunit assembly to form an enzymatically active multimer. By the use of the recombinant expression system, NHase activity 1.7 times higher than that of the original strain, R. rhodochrous J1, was achieved.
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    The effects of space flight on the production of monorden by Humicola fuscoatra WC5157 in solid-state fermentation (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 579-583 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of space flight on the production of the antibiotic monorden on two types of agar media, T8 and PG, by Humicola fuscoatra WC5157 was examined on board the US Space Shuttle mission STS-77 in May 1996. Paired space-flight and ground control samples were prepared using identical hardware, protocol, media, and inoculum. Inoculation occurred simultaneously for both groups 2.5 h after launch. The flight and ground samples were allowed to grow for the entire 10-day mission in a dark, thermally controlled (22 °C) environment. Post-flight HPLC analysis of the flight and ground sample extracts indicated that the production of monorden by H. fuscoatra WC5157 in the flight samples was higher than in the ground samples in both agar media. In the T8 medium, the production of monorden in the flight and ground samples was 11.6 ± 3.5 μg and 8.9 ± 1.1 μg respectively (30% increase). In the PG medium, the production of monorden in the flight and ground samples was 23.8 ± 3.3 μg and 8.2 ± 2.2 μg respectively (190% increase). The production of monorden in the flight and ground control samples was confirmed by HPLC-MS analysis.
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    URL: http://dx.doi.org/10.1007/s002530051216
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    Production of d-hydantoinase by halophilic Pseudomonas sp. NCIM 5109 (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 594-599 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract About 1000 bacterial colonies isolated from sea water were screened for their ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine as a criterion for the determination of hydantoinase activity. The strain M-1, out of 11 hydantoinase-producing strains, exhibited the maximum ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine. The strain M-1 appeared to be a halophilic Pseudomonas sp. according to morphological and physiological characteristics. Optimization of the growth parameters revealed that nutrient broth with 2% NaCl was the preferred medium for both biomass and enzyme production. d-Hydantoinase of strain M-1 was not found to be inducible by the addition of uracil, dihydrouracil, β-alanine etc. The optimum temperature for enzyme production was about 25 °C and the organism showed a broad pH optimum (pH 6.5–9.0) for both biomass and hydantoinase production. The organism seems to have a strict requirement of NaCl for both growth and enzyme production. The optimum pH and temperature of enzyme activity were 9–9.5 and 30 °C respectively. The biotransformation under the alkaline conditions allowed the conversion of 80 g l−1 dl-5-phenylhydantoin to 82 g l−1 d(−)N-carbamoylphenylglycine within 24 h with a molar yield of 93%.
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    URL: http://dx.doi.org/10.1007/s002530051219
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    Isolation and characterization of two bacteriocins of Lactobacillus acidophilus LF221 (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 606-612 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Lactobacillus acidophilus LF221 produced bacteriocin-like activity against different bacteria including some pathogenic and food-spoilage species. Besides some lactic acid bacteria, the following species were inhibited: Bacillus cereus, Clostridium sp., Listeria innocua, Staphylococcus aureus, Streptococcus D. L. acidophilus LF221 produced at least two bacteriocins, acidocin LF221 A and acidocin LF221 B, which were purified by ammonium sulphate precipitation, ion-exchange chromatography, hydrophobic interaction and reverse-phase FPLC. The antibacterial substances were heat-stable, sensitive to proteolytic enzymes (trypsin, pepsin, pronase, proteinase K) and migrated as 3500- to 5000-Da proteins on sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The sequences of 46 amino-terminal amino acid residues of peptide A and 35 of peptide B were determined. Among the residues identified, no modified amino acids were found. No significant homology was found between the amino acid sequences of acidocin LF221 A and other bacteriocins of lactic acid bacteria and 26% homology was found between acidocin LF221 B and brevicin 27. L. acidophilus LF221 may be of interest as a probiotic strain because of its human origin and inhibition of pathogenic bacteria, especially Clostridium difficile.
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    URL: http://dx.doi.org/10.1007/s002530051221
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    Bacterial growth in space flight: logistic growth curve parameters for Escherichia coli and Bacillus subtilis (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 229-234 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Previous investigations have reported that bacterial suspension cultures grow to higher stationary concentrations in space flight than on Earth; however, none of these investigations included extensive ground controls under varied inertial conditions. This study includes extensive controls and cell-growth data taken at several times during lag phase, log phase, and stationary phase of Escherichia coli and Bacillus subtilis. The Marquardt-Levenberg, least-squares fitting algorithm was used to calculate kinetic growth parameters from the logistic bacterial growth equations for space-flight and control growth curves. Space-flight cultures grew to higher stationary-phase concentrations and had shorter lag-phase durations. Also, evidence was found for increased exponential growth rate in space.
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    URL: http://dx.doi.org/10.1007/s002530051386
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    Effects of yeast extract on the production and the quality of the exopolysaccharide, zooglan, produced by Zoogloea ramigera 115SLR (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 235-240 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Although many studies have examined the influence of culture conditions on the production and composition of polysaccharides, little is known about the factors influencing the quality of exopolysaccharides (EPS). In this work we studied the effect of yeast extract on the production, composition and molecular weight of the EPS zooglan produced by Zoogloea ramigera 115SLR. This bacterium was grown on a new completely defined synthetic medium and on a medium containing yeast extract. Growth and polysaccharide production performances were comparable on the two media with a glucose to exopolysaccharide conversion yield of 35% (g/g). The polysaccharides produced on these two media have an identical composition but a different molecular weight and molecular weight distribution. The yeast extract medium leads to a more homogeneous polysaccharide solution.
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    URL: http://dx.doi.org/10.1007/s002530051387
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  • 86
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    Hydroxylamine oxidation and subsequent nitrous oxide production by the heterotrophic ammonia oxidizer Alcaligenes faecalis (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 255-261 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Nitrous oxide (N2O), a greenhouse gas, is emitted during autotrophic and heterotrophic ammonia oxidation. This emission may result from either coupling to aerobic denitrification, or it may be formed in the oxidation of hydroxylamine (NH2OH) to nitrite (NO2 −). Therefore, the N2O production during NH2OH oxidation was studied with Alcaligenes faecalis strain TUD. Continuous cultures of A. faecalis showed increased N2O production when supplemented with increasing NH2OH concentrations. 15N-labeling experiments showed that this N2O production was not due to aerobic denitrification of NO2 −. Addition of 15N-labeled NH2OH indicated that N2O was a direct by-product of NH2OH oxidation, which was subsequently reduced to N2. These observations are sustained by the fact that NO2 − production was low (0.23 mM maximum) and did not increase significantly with increasing NH2OH concentration in the feed. The NH2OH-oxidizing capacity increased with increasing NH2OH concentrations. The apparent V max and K m were 31 nmol min−1 mg dry weight−1 and 1.5 mM respectively. The culture did not increase its growth yield and was not able to use NH2OH as the sole N source. A non-haem hydroxylamine oxidoreductase was partially purified from A. faecalis strain TUD. The enzyme could only use K3Fe(CN)6 as an electron acceptor and reacted with antibodies raised against the hydroxylamine oxidoreductase of Thiosphaera pantotropha.
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    Oxidation of aromatic alcohols by laccase from Trametes versicolor mediated by the 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) cation radical and dication (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 267-276 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Oxidation of aromatic alcohols, such as non-phenolic lignin model compounds, by oxidised species of 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) has been investigated. The cation radical and dication formed from ABTS were both capable of oxidising aromatic alcohols to aldehydes. The reactions terminated at the level of the aldehyde and no acids were formed. The cation radical and dication worked in a cycle as an electron-transfer compound between an oxidant and alcohol. In addition to the oxidation of the primary benzyl-hydroxyl group, an oxidation of the secondary α-hydroxyl group to the ketone by the dication was possible. All distinguishing features of these reactions corresponded to the results of the oxidation performed by the laccase of Trametes versicolor in the presence of ABTS. The decomposition products from the dication alone and ABTS with laccase confirmed the supposition that the dication was involved in the laccase mediator system. A reaction mechanism based on deprotonation of the alcohol cation radical was predicted to play a key role in the irreversible followup reaction and to be the driving force of the process.
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    URL: http://dx.doi.org/10.1007/s002530051392
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    Complete transformation of 1,1,1-trichloroethane to chloroethane by a methanogenic mixed population (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 277-283 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A methanogenic mixed population in a packed-bed reactor completely transformed 1,1,1-trichloroethane (10 μM) to chloroethane by a cometabolic process. Chloroethane was not further transformed. Acetate and methanol served as electron donors. Complete transformation of 1,1,1-trichloroethane to chloroethane only occurred when sufficient electron donor was fed into the reactor. Otherwise, besides chloroethane, 1,1-dichloroethane was also found as a product. The products of 1,1,1-trichloroethane transformation also depended on the type of electron donor present. With acetate, the degree of dechlorination was higher, i.e. more 1,1,1-trichloroethane was transformed to chloroethane than with methanol. In an enrichment culture obtained from the reactor contents, 1,1,1-trichloroethane was only transformed to 1,1-dichloroethane and was not further metabolized. Methanol, acetate, formate, ethanol, 2-propanol, trimethylamine and H2, but not dimethylamine and methylamine, served as electron donors for 1,1,1-trichloroethane transformation by this enrichment culture. Both nitrate and nitrite inhibited 1,1,1-trichloroethane transformation; while nitrate completely inhibited 1,1,1-trichloroethane dechlorination, some conversion did occur in the presence of nitrite. The product(s) of this conversion remain unknown, since no chlorinated hydrocarbons were detected.
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    Aerobic 4-nitrophenol degradation by microorganisms fixed in a continuously working aerated solid-bed reactor (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 284-290 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Studies of microbial purification of a model waste water containing 4-nitrophenol were carried out in a continuously working aerobic solid-bed reactor. The main emphasis was on the dynamic behaviour of the system after a sudden change in cultivation conditions and on the steady-state performance of the reactor as a function of the pollution load. A change from ammonium-free to ammonium-containing medium hardly influenced the nitrophenol degradation. The reactor responded differently to an increase in pollutant load, which was brought about by increasing either the 4-nitrophenol content or the flow of the waste water. Up to a load of 270 mg l−1 h−1 the pollutant was stably and almost completely degraded. At a higher load, only a partial 4-nitrophenol degradation took place. A mathematical model was derived to describe the processes that occurred in the reactor. By segregation into two compartments – the aqueous phase and the biofilm – account was taken of the fact that the pollutant is carried into the biofilm by diffusion and is degraded there. The observed relations between the pollutant load, the pollutant concentration in the outlet of the reactor and the reactor performance agreed with the simulated process behaviour. As the model simulation showed, the incomplete pollutant degradation at a higher reactor load was caused by oxygen limitation.
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    URL: http://dx.doi.org/10.1007/s002530051394
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    Influence of microbial concentration on the rheology of non-Newtonian fermentation broths (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 310-315 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The objective of this study was to quantify the effect of fungal biomass concentration on the rheology of non-Newtonian fermentation systems. Batch fermentations of Penicillium chrysogenum were carried out with glucose as the sole carbon source. The flow behavior of the system was characterized at various fermentation times and was adequately described by the power-law model. The apparent viscosity of the fermentation broth was significantly affected by biomass concentrations in the fermenter. Fermentation broths containing 17.71 g/l biomass as dry weight were characterized by an apparent viscosity of 0.25 Pa s at a shear rate of 50 s−1. Microbial concentration also affected the power-law flow-behavior index and the consistency index. The value of the consistency index ranged from 0.002 Pa s n at a biomass concentration of 0.1 g/l to 6.14 Pa s n at a biomass concentration of 17.71 g/l. The flow-behavior index decreased from an initial value of 1 to a final value of 0.17. Simple empirical correlations have been proposed to quantify the dependence of the power-law parameters on fungal biomass concentration. Experimental data obtained in this study were accurately described by these correlations. The general applicability of these relationships was tested, using previously published rheological data on Aspergillus awamori and Aspergillus niger fermentation broths, and good agreement was seen between experimental data and the predictions from the empirical correlations.
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    Microbial production, purification, and characterization of (S)-specific N-acetyl-2-amino-1-phenyl-4-pentene amidohydrolase from Rhodococcus globerulus K1/1 (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 12-18 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rhodococcus globerulus K1/1 was found to express an inducible (S)-specific N-acetyl-2-amino-1-phenyl-4-pentene amidohydrolase. Optimal bacterial growth and amidohydrolase expression were both observed at about pH 6.5. Purification of the enzyme to a single band in a Coomassie blue-stained SDS-PAGE gel was achieved by nucleic acid and ammonium sulfate precipitation of Rhodococcus globerulus K1/1 crude extract and column chromatography on TSK Butyl-650(S) Fractogel and Superose 12HR. The amidohydrolase was purified to a homogeneity leading to a tenfold increase of the specific activity with a recovery rate of 65%. At pH 7.0 and 23 °C the enzyme showed no loss of activity after 30 days incubation. The amidohydrolase was stable up to 55 °C. The enzyme was inhibited strongly only by 10 mM Zn2+ among the tested metal cations and was inhibited 100% by 0.01 mM phenylmethanesulfonyl fluoride. The molecular weight of the native enzyme was estimated to be 92 kDa by gel filtration and 55 kDa by SDS-PAGE, suggesting a homodimeric structure.
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    URL: http://dx.doi.org/10.1007/s002530051607
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    Metabolic approaches for the optimisation of recombinant fermentation processes (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 43-50 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The aim of this work was the establishment of a novel method to determine the metabolic load on host-cell metabolism resulting from recombinant protein production in Escherichia coli. This tool can be used to develop strategies to optimise recombinant fermentation processes through adjustment of recombinant-protein expression to the biosynthetic capacity of the host-cell. The signal molecule of the stringent-response network, guanosine tetraphosphate (ppGpp), and its precursor nucleotides were selected for the estimation of the metabolic load relating to recombinant-protein production. An improved analytical method for the quantification of nucleotides by ion-pair, high-performance liquid chromatography was established. The host-cell response upon overexpression of recombinant protein in fed-batch fermentations was investigated using the production of human superoxide dismutase (rhSOD) as a model system. E. coli strains with different recombinant systems (the T7 and pKK promoter system) exerting different loads on host-cell metabolism were analysed with regard to intracellular nucleotide concentration, rate of product formation and plasmid copy number.
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    Isolation and characterisation of a ropy Lactobacillus strain producing the exopolysaccharide kefiran (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 69-74 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A capsular-polysaccharide-producing strain, LM-17, was isolated from kefir grains and was identified as a slime-forming, rod-shaped Lactobacillus. According to 1H- and 13C-NMR spectral data, the exopolysaccharide produced by the isolated bacterial strain is identical to the glucogalactan extracted from kefir grains and therefore known as kefiran. The kefiran produced was characterised by means of viscosity, optical rotatory power, circular dichroism and IR spectral measurements. A batch procedure was set up for the culture and extraction of the exopolysaccharide in laboratory conditions, resulting in a yield of 2 g/l purified kefiran from the culture supernatant of the LM-17 strain.
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    Lactobacillus sanfranciscensis CB1: manganese, oxygen, superoxide dismutase and metabolism (1999)
    Springer
    Applied microbiology and biotechnology 51 (1999), S. 358-363 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The latency phase, growth rate, cell yield and end-products of Lactobacillus sanfranciscensis CB1 were affected by oxygen and the supply of 225 μM Mn2+. Mn2+ was especially related to the highest substrate consumption. Aerobiosis and Mn2+ supply were responsible for the highest superoxide dismutase activity. An auto-inhibitory accumulation of H2O2 meant that the survival of air-grown cells supplied with Mn2+ rapidly decreased during the stationary phase. As shown by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, Mn2+ supply influenced protein expression. As shown by non-denaturating zymograms, Lb. sanfranciscensis CB1 expressed an approximately 12.5-kDa superoxide dismutase, which is probably Mn-dependent. The enzyme was insensitive to H2O2 treatment, was not induced by the presence of paraquat under aerobic conditions and was relatively stable at pH 4.0. Sourdoughs that contained high levels of oxygen enhanced cell growth, acidification and acetic acid production by Lb. sanfranciscensis CB1.
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    Bioassays for risk assessment of coal conversion products (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 127-130 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Traditional as well as biotechnological processing of coal leads to complex mixtures of products. Besides chemical and physical characterization, which provides the information for product application, there is a need for bioassays to monitor properties that are probably toxic, mutagenic or cancerogenic. Investigations carried out focused on the selection, adaptation and validation of bioassays for the sensitive estimation of toxic effects. Organisms like bacteria, Daphnia magna and Scenedesmus subspicatus, representing different complexities in the biosphere, were selected as test systems for ecotoxicological and mutagenicity studies. The results obtained indicate that bioassays are, in principle, suitable tools for characterization and evaluation of coal-derived substances and bioconversion products. Using coal products, coal-relevant model compounds and bioconversion products, data for risk assessment are presented.
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    Chemicals from biotechnology: molecular plant genetics will challenge the chemical and the fermentation industry (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 135-145 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Industrial biotechnology has evolved as a significant manufacturing tool for products like fuel-grade ethanol, organic acids and bulk amino acids, but most items are still speciality products for food and pharmaceutical applications. Current development projects within the chemical industry, including lactic acid and 1,3-propanediol based polymers and plastics, indicate that new biotechnological processes and products may soon approach the market place, clearly targeted at the leading petrochemical bulk outlets. This is flanked by a strategic shift by the major chemical companies in to “life sciences”–pharmaceuticals, agrochemicals and the seed business as well as biotech fine chemicals. The recent tremendous achievements in molecular plant genetics and transgenic crop breeding will boost agro-biotechnology, agriculture and renewable raw materials as compelling projects for chemistry and biotechnology. New plant-based production routes may challenge established chemical and biochemical domains, but at the same time open new horizons to valuable feedstocks, intermediates and end-products.
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    High- and low-molecular-mass microbial surfactants (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 154-162 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Microorganisms synthesize a wide variety of high- and low-molecular-mass bioemulsifiers. The low-molecular-mass bioemulsifiers are generally glycolipids, such as trehalose lipids, sophorolipids and rhamnolipids, or lipopeptides, such as surfactin, gramicidin S and polymyxin. The high-molecular-mass bioemulsifiers are amphipathic polysaccharides, proteins, lipopolysaccharides, lipoproteins or complex mixtures of these biopolymers. The low-molecular-mass bioemulsifiers lower surface and interfacial tensions, whereas the higher-molecular-mass bioemulsifiers are more effective at stabilizing oil-in-water emulsions. Three natural roles for bioemulsifiers have been proposed: (i) increasing the surface area of hydrophobic water-insoluble growth substrates; (ii) increasing the bioavailability of hydrophobic substrates by increasing their apparent solubility or desorbing them from surfaces; (iii) regulating the attachment and detachment of microorganisms to and from surfaces. Bioemulsifiers have several important advantages over chemical surfactants, which should allow them to become prominent in industrial and environmental applications. The potential commercial applications of bioemulsifiers include bioremediation of oil-polluted soil and water, enhanced oil recovery, replacement of chlorinated solvents used in cleaning-up oil-contaminated pipes, vessels and machinery, use in the detergent industry, formulations of herbicides and pesticides and formation of stable oil-in-water emulsions for the food and cosmetic industries.
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    A novel method for characterisation of microbial growth kinetics on volatile organic compounds (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 174-178 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A novel method for the determination of microbial growth kinetics on hydrophobic volatile organic compounds (VOC) has been developed. A stirred tank reactor was operated as a fed-batch system to which the VOC was continuously fed via the gas phase, assuring a constant VOC concentration in the mineral medium. A flow of air was saturated with the VOC, and then mixed with a further flow of air, to obtain a predetermined VOC concentration. Thus, different VOC concentrations in the mineral medium could be obtained by altering the VOC concentration in the feed gas. The growth kinetics of Xanthobacter autotrophicus GJ10 on 1,2-dichloroethane (DCE) and of Pseudomonas sp. strain JS150 on MonoChloroBenzene (MCB) were assessed using this method. The growth of strain JS150 was strongly inhibited at MCB concentrations higher than 160 mg l−1, and the results were fitted using a piecewise function. The growth kinetics of strain GJ10 were described by the Luong model where maximum growth rate μmax = 0.12 h−1, substrate saturation constant K S = 7.8 mg l−1, and maximum substrate concentration S m (above which growth is completely inhibited) = 1080 mg l−1. Varying nitrogen and oxygen flows enabled the effect of oxygen concentration on the growth kinetics of Pseudomonas JS150 to be determined.
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    URL: http://dx.doi.org/10.1007/s002530051505
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  • 99
    Electronic Resource
    Electronic Resource
    Viability and thermal stability of a strain of Saccharomyces cerevisiae freeze-dried in different sugar and polymer matrices (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 215-220 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The viability and thermal stability of a freeze-dried yeast strain were studied in relation to some physical properties of the matrices in which the cells were freeze-dried. Samples of inoculum with solutions of the matrix components [polyvinylpyrrolidone (PVP), maltose, trehalose, maltodextrins, or mixtures of maltodextrin and trehalose] and controls without matrices were freeze-dried and then equilibrated at several relative humidities. Viability was determined before and after freeze-drying and after heat treatment (100 min at 70 °C). Freeze-drying with trehalose, PVP, maltose or 1.8-kDa maltodextrin, and mixtures of maltodextrin/trehalose increased viability in comparison with controls. The 3.6-kDa maltodextrin was ineffective at protecting the cells during freeze-drying. The glass transition temperature (T g), which depends on moisture content, was indicated as a possible factor to determine the stability of labile materials. Protective effects of the excipients during thermal treatment were analysed in relation to the physical changes (collapse or structural shrinkage) which were dependent on the T g of the systems. The presence of a certain amount of amorphous disaccharides during freeze-drying and heating was found to be a critical factor for ensuring cell viability, which was protected even in rubbery (above T g) matrices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051511
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  • 100
    Electronic Resource
    Electronic Resource
    A β-1,4-endoglucanase-encoding gene from Cellulomonas pachnodae (1999)
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 232-239 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A gene library of Cellulomonas pachnodae was constructed in Escherichia coli and was screened for endoglucanase activity. Five endoglucanase-positive clones were isolated that carried identical DNA fragments. The gene, designated cel6A, encoding an endoglucanase enzyme, belongs to the glycosyl hydrolase family 6 (cellulase family B). The recombinant Cel6A had a molecular mass of 53 kDa, a pH optimum of 5.5, and a temperature optimum of 50–55 °C. The recombinant endoglucanase Cel6A bound to crystalline cellulose and beech litter. Based on amino acid sequence similarity, a clear cellulose-binding domain was not distinguished. However, the regions in the Cel6A amino acid sequence at the positions 262–319 and 448–473, which did not show similarity to any of the known family-6 glycosyl hydrolases, may be involved in substrate binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051514
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