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  • Articles  (34,973)
  • American Chemical Society  (23,696)
  • Springer  (11,277)
  • 1995-1999  (34,973)
  • 1998  (34,973)
  • Chemistry and Pharmacology  (33,143)
  • Process Engineering, Biotechnology, Nutrition Technology  (5,475)
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  • Articles  (34,973)
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  • 1995-1999  (34,973)
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  • 1
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    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 20 (1998), S. 328-332 
    ISSN: 1476-5535
    Keywords: Keywords: lipase; enzymatic synthesis; aromatic polyester; diacid; diol; polyesterification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic synthesis of aromatic polyesters by direct polyesterification between a diacid and a diol is described. The effects of the type of substrate, type and quantities of lipase, temperature, vacuum, and reaction time on the synthesis of aromatic polyesters were studied in detail. Among three lipases investigated, only Novozym 435 worked well for aromatic polyester synthesis. Temperature and vacuum played an important role in obtaining a high molar mass of the aromatic polyesters. Furthermore, with isophthalic acid and 1,6-hexanediol as substrates, the mass average molar mass of the polyester obtained increased with an increase in the lipase quantity up to 0.375 g (11.7%, w/w of total reactor contents). The mass average molar mass of the polyester was as high as 50000 g mol−1 in 168 h, with a polydispersity of PD ≈ 1.4.
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  • 2
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 344-353 
    ISSN: 1476-5535
    Keywords: Keywords: Acremonium chrysogenum; cephalosporin C; deacetoxycephalosporin C; 7-ACA; 7-ADCA; expandase/ hydroxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deacetoxycephalosporin C (DAOC) is produced by Acremonium chrysogenum as an intermediate compound in the cephalosporin C biosynthetic pathway, and is present in small quantities in cephalosporin C fermentation broth. This compound forms an undesirable impurity, 7-aminodeacetoxycephalosporanic acid (7-ADCA), when the cephalosporin C is converted chemically or enzymatically to 7-aminocephalosporanic acid (7-ACA). In the cephalosporin C biosynthetic pathway of A. chrysogenum, the bifunctional expandase/hydroxylase enzyme catalyzes the conversion of penicillin N to DAOC and subsequently deacetylcephalosporin C (DAC). By genetically engineering strains for increased copy number of the expandase/hydroxylase gene, we were able to reduce the level of DAOC present in the fermentation broth to 50% of the control. CHEF gel electrophoresis and Southern analysis of DNA from two of the transformants revealed that one copy of the transforming plasmid had integrated into chromosome VIII (ie a heterologous site from the host expandase/hydroxylase gene situated on chromosome II). Northern analysis indicated that the amount of transcribed expandase/hydroxylase mRNA in one of the transformants is increased approximately two-fold over that in the untransformed host.
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  • 3
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 323-327 
    ISSN: 1476-5535
    Keywords: Keywords: thermotolerance; process development; novel yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fermentation characteristics of the novel, thermotolerant, isolate Kluyveromyces marxianus var marxianus were determined to evaluate its aptitude for use in an ethanol production process. Sustainable growth was not observed under anaerobic conditions, even in the presence of unsaturated fatty acid and sterol. A maximum ethanol concentration of 40 g L−1 was produced at 45°C, with an initial specific ethanol production rate of 1.7 g g−1 h−1. This was observed at ethanol concentrations below 8 g L−1 and under oxygen-limited conditions. The low ethanol tolerance and low growth under oxygen-limited conditions required for ethanol production implied that a simple continuous process was not feasible with this yeast strain. Improved productivity was achieved through recycling biomass into the fermenter, indicating that utilising an effective cell retention method such as cell recycle or immobilisation, could lead to the development of a viable industrial process using this novel yeast strain.
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  • 4
    ISSN: 1476-5535
    Keywords: Keywords: carbon concentration; Colletotrichum coccodes; conidiation; C:N ratio; mycoherbicide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of carbon concentration and carbon-to-nitrogen ratio (C:N) as well as their interaction on Colletotrichum coccodes growth and sporulation in submerged flask culture were evaluated. When C:N ratios were held constant, both mycelial dry biomass and spore yield increased with increasing carbon concentration. The specific spore yields (spore yield g−1 carbon), however, were not significantly different for the same C:N ratio in most cases. The highest spore yields (1.3 × 108 spores per ml) were obtained from media containing 20 g per liter carbon with C:N ratios ranging from 5:1 to 10:1. When the C:N ratio was greater than 15:1, spore yields were significantly decreased with increasing C:N ratios. High carbon concentration (20 g L−1) combined with high C:N ratios (above 15:1) reduced both mycelial growth and sporulation, and increased spore matrix production. Spores produced in medium containing 10 g L−1 carbon with C:N ratios from 10:1 to 15:1 had 90% germination on potato dextrose agar after 12 h and caused extensive shoot dry weight reduction on the target weed, velvetleaf. These results suggest that C:N ratios from 10:1 to 15:1 are optimal for C. coccodes spore production.
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  • 5
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 275-280 
    ISSN: 1476-5535
    Keywords: Keywords: microbial biofilms; modified Robbins device (MRD); antifouling paint; tributyltin (TBT); copper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of biofilms of Pseudomonas aeruginosa PAO-1 was studied using modified Robbins devices. Biofilm development was measured using viable counts, acridine orange direct counts (AODC), and a colorimetric method for exopolysaccharide (EPS). Biofilms reached their maximum population 24–72 h after inoculation on coupons with no paint or on coupons coated with marine paint VC-18 without additives. Biofilms on stainless steel contained higher numbers of total cells and of viable cells than biofilms on fiberglass or aluminum. Coating the surfaces with marine paint VC-18 resulted in decreased numbers of cells on stainless steel but had little effect on numbers of cells on fiberglass or aluminum. Addition to the paint of Cu or tributyltin (TBT), the active components in two types of antifouling paints, inhibited the initial development of biofilms. However, by 72–96 h, most biofilms contained the same number of cells as surfaces without additives as shown by both viable counts and AODC. Biofilms that formed on surfaces coated with Cu- or TBT-containing paint did not synthesize more EPS, suggesting that P. aeruginosa PAO-1 does not respond to these compounds by synthesizing more EPS, which could bind the metal and protect the cells. Rather, these biofilms may contain Cu- or TBT-resistant cells. TBT-resistant cells made up 1–10% of the viable counts in biofilms on uncoated stainless steel, but in biofilms on stainless steel coated with marine paint containing TBT, TBT-resistant cells made up as much as 50% of the population. For non-coated stainless steel surfaces, Cu-resistant cells initially made up the majority of the population, but after 48 h they made up less than 1% of the population. On Cu-coated stainless steel, Cu-resistant cells predominated through 48 h, but after 48 h they comprised less than 10% of the population. These results suggest that the growth of TBT-resistant and Cu-resistant cells contributes to biofilms of P. aeruginosa PAO-1 at early stages of development but not at later stages.
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  • 6
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 339-343 
    ISSN: 1476-5535
    Keywords: Keywords: chemostat; Candida shehatae; mixed sugars; D-xylose; Monod kinetics; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of biomass formation, D-xylose utilization, and mixed substrate utilization were determined in a chemostat using the yeast Candida shehatae. The maximum growth rate of C. shehatae grown aerobically on D-xylose was 0.42 h−1 and the Monod constant, K s, was 0.06 g L−1. The biomass yield, Y {X/S}, ranged from 0.40 to 0.50 g g−1 over a dilution rate range of 0.2–0.3 h−1, when C. shehatae was grown on pure D-xylose. Mixtures of D-xylose and glucose (∼1 : 1) were simultaneously utilized over a dilution rate from 0.15 to 0.35 h−1 at pH 3.5 and 4.5, but pH 3.5 reduced μmax and reduced the dilution rate range over which D-xylose was utilized in the presence of glucose. At pH 4.5, μmax was not reduced with the mixed sugar feed and the overall or lumped K s value was not significantly increased (0.058 g L−1 vs 0.06 g L−1), when compared to a pure D-xylose feed. Kinetic data indicate that C. shehatae is an excellent candidate for chemostat production of value added products from renewable carbon sources, since simultaneous mixed substrate utilization was observed over a wide range of growth rates on a 1 : 1 mixture of glucose and D-xylose.
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  • 7
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 373-375 
    ISSN: 1476-5535
    Keywords: Keywords: Actinomadura; compactin; hydroxylase; microbial transformation; pravastatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydroxylase in cell-free extracts of Actinomadura sp strain 2966 converts compactin to pravastatin. It requires NADPH as coenzyme and Mg2+ as cofactor; Mn2+ can partially replace Mg2+. In contrast with the inducible cytochrome P-450 system of Streptomyces carbophilus which catalyzes the same overall reaction, this constitutive hydroxylase is stimulated by ATP and ascorbic acid and is not inactivated by CO.
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  • 8
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 377-378 
    ISSN: 1476-5535
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 9
    ISSN: 1476-5535
    Keywords: Keywords: hirudin; Hansenula polymorpha; methylotrophic yeast; methanol oxidase; autonomously replicating sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various recombinant Hansenula polymorpha strains were developed and compared for their level of expression of the anticoagulant hirudin. H. polymorpha DL1-57 harboring an autonomously replicating sequence, HARS36, efficiently expressed the gene for recombinant hirudin. The effect of methanol oxidase (MOX) on the expression of the hirudin gene in H. polymorpha DL1-57 was studied, and the fermentation strategies coupled with the MOX activity and an antioxidant, tocopherol, were also examined.
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  • 10
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 19-21 
    ISSN: 1476-5535
    Keywords: Keywords: yogurt; Lactobacillus bulgaricus; Streptococcus thermophilus; Lactobacillus acidophilus; Bifidobacterium spp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The microbiological quality of four brands of natural yogurts and two probiotic yogurts available in the Portuguese market, was evaluated during the shelf-life period. Although the specific flora decreased during storage it was always within the range of recommended values. No coliforms and an insignificant number of fungi were detected.
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  • 11
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 6-10 
    ISSN: 1476-5535
    Keywords: Keywords: cytoplasmic membrane; biocides; potassium leakage; Escherichia coli; Pseudomonas aeruginosa; Pseudomonas-gap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many antimicrobial compounds exhibit bacterial cell membrane activity as either potassium ion leakage and/or leakage of material that absorbs at 260 nm from the cell. In this experiment a potassium ion selective electrode and spectophotometric observation of 260-nm leakage were used in order to examine cell membrane effects in a selection of common biocides upon both Escherichia coli NCIMB 10000 and Pseudomonas aeruginosa NCIMB 10548. The observation of potassium ion leakage for pyrithione biocides yielded results which were initially difficult to interpret, but are thought to suggest a species-dependent combination of potassium ion leakage from affected membranes and chelation of those leaked ions in the bathing suspension. Such a result is not, however, supported by the 260-nm material leakage results, which indicate very similar levels of membrane active effects for both species of bacteria.
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  • 12
    ISSN: 1476-5535
    Keywords: Keywords: Alcaligenes eutrophus; biodegradable plastics; poly(β-hydroxybutyrate); vegetable oil; Vernonia galamensis; vernolic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Saponified vernonia oil was converted exclusively to poly(β-hydroxybutyrate) (PHB) by Alcaligenes eutrophus in a single-stage batch culture. After harvesting, centrifugation followed by lyophilization, the resulting dried cells contained up to 42.8 wt% PHB having a peak molecular mass of 381 863 Da, weight-average molecular mass of 308 390 Da, and a polydispersity of 1.1. The PHB had a melting point (Tm) range of 163–174°C with a maximum at 172°C (lit. Tm, 175°C), and heat of fusion of 18.43 cal g−1. Fermentation performed under varying conditions of nitrogen limitation indicated that there was no significant effect of nitrogen concentration on the molecular mass of PHB produced from vernonia oil by A. eutrophus.
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  • 13
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 37-45 
    ISSN: 1476-5535
    Keywords: Keywords: glucosyltransferase; dextransucrase; alternansucrase; Leuconostoc mesenteroides; mutant; glucan; dextran; polysaccharide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mutant strain (R1510) of Leuconostoc mesenteroides B-1355 was isolated which synthesized primarily an insoluble polysaccharide and little soluble polysaccharide when grown in sucrose-containing medium. Glucose or sucrose cultures of this strain produced a single intense band of GTF-1 activity of 240 kDa on SDS gels, and a number of faint, smaller bands. Oligosaccharides synthesized by strain R1510 from methyl-α-D-glucoside and sucrose included a trisaccharide whose structure contained an α(1→2) glucosidic linkage. This type of linkage has not been seen before in any products from strain B-1355 or its mutant derivatives. The structure of the purified trisaccharide was confirmed by 13C-nuclear magnetic resonance. The insoluble polysaccharide also contained α(1→2) branch linkages, as determined by methylation analysis, showing that synthesis of the linkages was not peculiar to methyl-α-D-glucoside. GTF-1, which had been excised with a razor blade from an SDS gel of a culture of the parent strain B-1355, produced the same trisaccharides as strain R1510, showing that GTF-1 from the wild-type strain was the same as GTF-1 from strain R1510. Mutant strains resembling strain R1510, but producing a single intense band of alternansucrase (200 kDa) instead of GTF-1 were also isolated, suggesting that mutations may be generated which diminished the activities for any two of the three GTFs of strain B1355 relative to the third. Strain R1554 produced a soluble form of alternansucrase, while strain R1588 produced a cell-associated form. The mechanism(s) by which specific GTFs become associated with the cells of L. mesenteroides was not explored.
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  • 14
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 75-80 
    ISSN: 1476-5535
    Keywords: Keywords: lipase; Pseudomonas aeruginosa; wastewater treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipase from Pseudomonas aeruginosa LP602, a bacterial strain isolated from a domestic wastewater sample, was preliminarily characterized. The enzyme exhibited maximum lipolytic activity at pH 8.0 where it was also stably maintained. At 55°C, the lipase had the highest activity but not stability. The enzyme was insensitive to EDTA and to many ions tested except Zn2+. It was sensitive to SDS but not to Tween-20, Tween-80 or Triton X-100. The enzyme was active towards a number of commercial food grade fats and oils. A suitable medium formula for lipase production was MMP containing 6.25% whey as a carbon source, 1% soybean oil as inducer and 0.5% yeast extract supplement. The culture was fed with glucose to a final concentration of 0.1% at the 15th hour of incubation. Lipase production under this condition was 3.5 U ml−1. Both P. aeruginosa LP602 cells and the lipase were shown to be usable for lipid-rich wastewater treatment.
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  • 15
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 92-98 
    ISSN: 1476-5535
    Keywords: Keywords: immunomagnetic separation; bovine feces; carcass wash water; apple cider; ground beef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Contamination of foods with pathogens such as Escherichia coli O157:H7 and Salmonella is a major concern worldwide and rapid, sensitive, and reliable methods are needed for detection of these organisms. Since these pathogens can contaminate similar foods and other types of samples, a multiplex polymerase chain reduction (PCR) was designed to allow simultaneous detection of both E. coli O157:H7 and Salmonella spp directly from enrichment cultures. Samples of apple cider, beef carcass wash water, ground beef, and bovine feces were inoculated with both E. coli O157:H7 and S. typhimurium at various bacterial levels. Following enrichment culturing for 20–24 h at 37°C in modified EC broth or buffered peptone water both containing novobiocin, the samples were subjected to a DNA extraction technique or to immunomagnetic separation then tested by the multiplex PCR assay. Four pairs of primers were employed in the PCR: primers for amplification of E. coli O157:H7 eaeA, stx 1/2 and plasmid sequences and for amplification of a portion of the Salmonella invA gene. Four fragments of the expected sizes were amplified in a single reaction and visualized following agarose gel electrophoresis in all the samples inoculated with ≤ 1 CFU g−1 or ml−1. Results can be obtained in approximately 30 h. The multiplex PCR is a potentially powerful technique for rapid and sensitive co-detection of both pathogens in foods and other types of samples.
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  • 16
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 150-166 
    ISSN: 1476-5535
    Keywords: Keywords: Cryptosporidium parvum; detection; PCR; environmental samples; water; food
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Since 1991 more than 30 PCR protocols have been published, which show a potential to replace the current microscopic detection method for Cryptosporidium parvum in environmental samples and food. This review provides a synoptic comparison of these protocols with respect to the following features: isolation and purification of oocysts from tested matrices, elimination of free DNA, viability and infectivity assessment, release of nucleic acids, nucleic acid extraction, type of PCR (PCR, RT-PCR, internal-standard-PCR, in situ PCR, TaqMan-PCR), primary product detection, additional specificity control, secondary product detection, reported sensitivity, cross-reaction with other Cryptosporidium species, and target and sequence information such as amplicon length, primer sequences, multiple copy target, presence of strain-specific differences in the amplicon, GenBank accession numbers and gene function. The results demonstrate that problems like PCR inhibition, viability assessment, and the requirement of an extreme sensitivity have been solved. PCR assays would be most valuable to control presence-absence standards in defined matrix volumes, and the setup of such standards would very much contribute to a rapid introduction of this awaited technology into routine monitoring of environmental, water and food samples, and to a further standardization of the various protocols. It can be expected that satisfactory solutions for quantification will be found for a growing number of PCR-based assays. Systematic field evaluation and interlaboratory studies will complement our present knowledge of these methods in the near future.
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  • 17
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 141-144 
    ISSN: 1476-5535
    Keywords: Keywords: Salmonella; pigs; ERIC PCR; epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purpose of this study was to test a protocol for a standardized ERIC PCR for its capability of genotyping Salmonella, isolated from pigs and their environment, in an epidemiologic approach. To test repeatability, four different Salmonella isolates were subjected to PCR three times. Furthermore, it was tested if the profiles on gel differed when a higher annealing temperature was used. Four Salmonella isolates were subjected to four different annealing temperatures (36, 40, 48 and 55°C). Moreover it was tested if the differentiation of Salmonella isolates, based on the genotypes, differed when a higher annealing temperature was used. Eight Salmonella isolates were tested at normal (36°C) and high (55°C) annealing temperatures. The results showed that this standardized ERIC PCR protocol was an efficient tool for typing many Salmonella isolates within a short period of time. The profiles were repeatable within one PCR reaction, but some profiles differed when they were compared between reactions. A higher annealing temperature resulted in profiles that contained more or fewer bands. The differentiation between isolates, when comparing profiles, remained the same. It was concluded that the standardized ERIC PCR protocol is useful for genotyping Salmonella.
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  • 18
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 175-177 
    ISSN: 1476-5535
    Keywords: Keywords: plasminogen activator inhibitor-2; baculovirus; expression vector; secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using pSXIVVI+X3 as an expressing vector, an occluded recombinant Trichoplusia ni nuclear polyhedrosis virus carrying the cDNA encoding plasminogen activators inhibitor-2 (PAI-2) under the control of the Syn and XIV promoters, has been constructed. SDS-PAGE and immunoblot analysis revealed that the virus-mediated PAI-2, with a molecular weight of ∼45 kDa, was synthesized in the Sf cells at a level of ∼16% of total intracellular protein and in the supernatant phase at a level of ∼64% of total extracellular protein secreted into the hemolymph of infected larvae. The expressed protein was similar to its authentic counterpart in terms of immunoreactivity and bioactivity.
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  • 19
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 187-191 
    ISSN: 1476-5535
    Keywords: Keywords: Clostridium beijerinckii; butanol; solvent production; corn steep water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Corn steep water (CSW) medium (1.6% solids plus 6% glucose) was evaluated for growth and butanol production by Clostridium beijerinckii NCIMB 8052 wild-type and hyper-amylolytic, hyper-butanol-producing mutant strain BA101. CSW alone was not a suitable substrate, whereas addition of glucose supported growth and butanol production by both strains. In a batch-scale fermentation using an optimized 6% glucose-1.6% solids CSW medium, C. beijerinckii NCIMB 8052 and strain BA101 produced 10.7 g L−1 and 14.5 g L−1 of butanol, respectively. The total solvents (acetone, butanol, and ethanol) produced by C. beijerinckii NCIMB 8052 and strain BA101 were 14 g L−1 and 20 g L−1, respectively. Initial fermentation in small-scale flasks containing 6% maltodextrin-1.6% solids concentration CSW medium resulted in 6 g L−1 and 12.6 g L−1 of butanol production by C. beijerinckii NCIMB 8052 and strain BA101, respectively. CSW can serve as an economic source of nitrogen, vitamins, amino acids, minerals, and other nutrients. Thus, it is feasible to use 6% glucose-1.6% solids CSW medium in place of semi-defined P2 medium.
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  • 20
    ISSN: 1476-5535
    Keywords: Keywords: human epidermal growth factor; Bacillus brevis recombinants; expanded bed adsorption; fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant Bacillus brevis which carried an expression plasmid encoding the human epidermal growth factor (EGF) gene on a cryptic high-copy number plasmid, pHT926, extracellularly produced EGF in its biologically active form at a concentration of over 1.5 g L−1 in the culture broth in a 30-L jar fermenter. The culture broth also contained some other EGF compounds, which mainly consisted of oligomeric and polymeric forms with disulfide bonds. We developed a simple purification method for EGF, without prior cell removal from the culture broth, comprising cation exchange expanded bed adsorption followed by ultrafiltration with UF 10 000 and 3000 membranes. The EGF compounds were efficiently separated from the EGF in its native form in the expanded bed adsorption step. With this purification method, only EGF in its native form was recovered from the culture broth, with a yield of nearly 80%, and 90% purity. This efficient and economic system has made it possible to use EGF as a pharmaceutical in the livestock industry.
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  • 21
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 225-227 
    ISSN: 1476-5535
    Keywords: Keywords: azaarenes; biotransformation; fungi; heterocyclic compounds; N-oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cultures of the fungi Cunninghamella elegans and Aspergillus niger were grown in fluid Sabouraud medium at 28°C for 3 days and then dosed with cinnoline (1,2-diazanaphthalene). After 3 more days, metabolites were extracted from the cultures with ethyl acetate, separated by high-performance liquid chromatography, and identified by mass spectrometry and proton nuclear magnetic resonance spectroscopy. Both fungi oxidized 2–10% of the added cinnoline to mixtures of cinnoline 2-oxide and cinnoline 1-oxide.
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  • 22
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 242-246 
    ISSN: 1476-5535
    Keywords: Keywords: xanthan; agricultural wastes; Xanthomonas campestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Four different acid-hydrolyzed wastes, from melon, watermelon, cucumber and tomato were compared for xanthan production. Growth of Xanthomonas campestris, xanthan biosynthesis, kinetics and chemical composition were investigated. Both growth and xanthan production were dependent on the acid hydrolysate concentrations and available nitrogen. Melon acid hydrolyzed waste was the best substrate for xanthan production. Exopolysaccharide obtained throughout this study was compared to commercial xanthan, showing a very similar chemical composition. Acid hydrolyzed wastes are proposed as a new carbon source for xanthan production.
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  • 23
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 289-291 
    ISSN: 1476-5535
    Keywords: Keywords: hNGF; Luc; PCR; baculovirus system; transfer vector; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Human nerve growth factor (hNGF) gene was proliferated with human leucocyte DNA as template by PCR. Then a fusion gene coding hNGF and luciferase (Luc) cDNAs was inserted into transfer vector pSXIVVI+X3/3 with the control of Syn XIV promoter. Luc and hNGF were simultaneously synthesized in Spodoptera larvae upon infection with a recombinant baculovirus, TnNPV-Luc-NGF-OCC+. Densitometric scanning of SDS-PAGE revealed that ∼18% of the total Coomassie blue-stainable protein of the infected larvae was represented by Luc protein, while the hNGF level was ∼8%. Both proteins were similar to their authentic counterparts in terms of immunoreactivity.
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  • 24
    ISSN: 1476-5535
    Keywords: Keywords: Fab antibody expression; E. coli fermentation; immobilized metal affinity chromatography (IMAC); proteases; botulinum toxin; temperature sensitivity
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant E. coli clones expressing a 50-kDa poly-histidine tail tagged antibody fragment against botulinum toxin (bt-Fab) were initially screened for yield and binding affinity. One clone was selected for bioprocess development. The selected bt-Fab vector was induced by addition of IPTG and the protein was targeted to the periplasm by inclusion of a pelB leader sequence. A histidine6 affinity ligand at the heavy chain C-terminus facilitated single-step purification by immobilized metal-affinity chromatography (IMAC). Notably, the effects of post-induction temperature on bt-Fab expression and downstream purification were evaluated. Our results demonstrated that fermentation conditions interfered with purification on the IMAC column at 37°C. Protease analysis by gelatin polyacrylamide gel electrophoresis (GPAGE) indicated the presence of a membrane-bound ∼39 kDa protease activity shortly after induction. The appearance of the protease activity was inversely correlated with the bt-Fab yield. The protease was purified and was shown to degrade bt-Fab. A simple kinetic model was developed describing temporal regulation of protease and bt-Fab degradation. Partially degraded bt-Fab was unrecoverable by IMAC, presumably due to the loss of the His6 affinity ligand. The amount of purified bt-Fab obtained per liter of fermentation broth was typically ∼1 mg.
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  • 25
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 261-274 
    ISSN: 1476-5535
    Keywords: Keywords: biofilms; stainless steel; Baltic Sea; ennoblement; CLSM; in situ hybridization; fluorescent beads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: ca 400 mV), the biofilm on the steel surface was characterized using confocal laser scanning microscopy (CLSM) in combination with functional and phylogenetic stains. The biofilm consisted of microbial cell clusters covering 10–20% of the surface. The clusters were loaf-formed, with a basal diameter of 20–150 μm, 5–20 per mm−2, each holding 〉104 cells in a density of 1–5 × 107 cells mm−3. The typical cluster contained mainly small Gram-negative bacteria (binding the EUB338 probe when hybridized in situ on the steel surface), and often carried one to three spherical colonies, either homogeneously composed of large Gram-negative cocci or more often small bacterial rods in high density, 108–109 cells mm−3. The clusters in live biofilms contained no pores, and clusters over 25 μm in diameter had a core nonpenetrable to fluorescent nucleic acid stains and ConA lectin stain. Fluorescently-tagged ConA stained cells at a depth of 〈5 μm, indicating the presence of cells with α-d-mannosyl and α-d-glucosyl residues on surfaces. ethidium bromide (log K ow −0.38) penetrated deeper (17 μm in 15 min, corresponding to 〉10 cells in a stack) into the cluster than did the less polar dyes SYTO 16 (log K ow 1.48) and acridine orange (log K ow 1.24), which stained five cells in a stack. Fluorescent hydrophobic and hydrophilic latex beads (diameter 0.02, 0.1 or 1.0 μm) coated patchwise the cluster surface facing the water, but penetrated only to depths of ⩽2 μm indicating a permeability barrier. About 1/3 of the stainable cells hybridized in situ with Alf1b, while fewer than 1/7 hybridized to GAM42, probes targeted towards α- and γ-Proteobacteria, respectively. Our results represent a microscopic description of an ennobling biofilm, where the ennoblement could follow the sequence of redox events as suggested by the model of Dickinson and Lewandowski (1996) for the structure of corrosive biofilms on a steel surface.
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  • 26
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 331-331 
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  • 27
    ISSN: 1476-5535
    Keywords: Keywords: bacterial inoculum; consortium; crude oil biodegradation; oil spill bioremediation agents; petroleum
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    Notes: Six crude oil-degrading bacterial strains isolated from different soil and water environments were combined to create a defined consortium for use in standardized efficacy testing of commercial oil spill bioremediation agents (OSBA). The isolates were cryopreserved in individual aliquots at pre-determined cell densities, stored at −70°C, and thawed for use as standardized inocula as needed. Aliquots were prepared with precision (typically within 10% of the mean) ensuring reproducible inoculation. Five of the six strains displayed no appreciable loss of viability during cryopreservation exceeding 2.5 years, and five isolates demonstrated stable hydrocarbon-degrading phenotypes during inoculum preparation and storage. When resuscitated, the defined consortium reproducibly biodegraded Alberta Sweet Mixed Blend crude oil (typically ± 7% of the mean of triplicate cultures), as determined by quantitative gas chromatography–mass spectrometry of various analyte classes. Reproducible biodegradation was observed within a batch of inoculum in trials spanning 2.5 years, and among three batches of inoculum prepared more than 2 years apart. Biodegradation was comparable after incubation for 28 days at 10°C or 14 days at 22°C, illustrating the temperature tolerance of the bacterial consortium. The results support the use of the synthetic consortium as a reproducible, predictable inoculum to achieve standardized efficacy tests for evaluating commercial OSBA.
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  • 28
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 121-127 
    ISSN: 1476-5535
    Keywords: Keywords: species identification; animal tissues; PCR; DNA fingerprinting
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most DNA methods for species identification of animal tissues test the presence/absence of one species per assay, requiring several tests for a complete analysis and prior knowledge of the species that are potentially present in the sample. Here we demonstrate that PCR with fluorescently labeled MIR (mammalian-wide interspersed repeat) primers generate fingerprints that are suitable for rapid identification of known and unknown species on an automatic sequencing apparatus and with computer-assisted data processing. The method allows the analysis of processed meat samples and offers a convenient alternative to sequencing of mitochondrial DNA.
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  • 29
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 128-140 
    ISSN: 1476-5535
    Keywords: Keywords: quantitative PCR; competitive PCR; MPN-PCR; low template; bias; polymerase chain reaction; environmental microbiology
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The application of PCR techniques in environmental and industrial microbiology is complicated by innumerable organic and inorganic contaminants and enzyme inhibitors that copurify with nucleic acids. These complications are compounded in quantitative PCR (qPCR) methods, which are predicated upon subtle yet significant assumptions of amplification efficiency and the representativeness of the sample with respect to the environment or industrial process from which it was obtained. In low-biomass and/or low-template situations, additional concerns related to target gene spatial heterogeneity in the sample, differential DNA (or RNA) extraction efficiency, molecular sampling error, attenuation of PCR inhibitors and amplification bias can quickly undermine fundamental assumptions of conventional competitive PCR (cPCR) and most-probable-number PCR (MPN-PCR) formats. A critical evaluation of cPCR and MPN-PCR assumptions is therefore presented within the context of environmental microbiology and low-template enumerations. Fundamental conclusions from the analysis of qPCR assumptions are that: (a) environmental qPCR enumerations are invariably estimates, not absolute enumerations, which are relative to the PCR standard; (b) traditional cPCR assays are ill-suited for environmental applications, especially in low-biomass situations; and (c) both cPCR and traditional MPN-PCR practices insufficiently account for field-scale, process-level or experimental variations that arise and become amplified in PCR enumerations. Thus, sample representativeness and errors related to sample replication are frequently more important than errors related to the qPCR assay itself. Based upon this critique of qPCR assumptions, an alternate qPCR method for routine environmental application is described which is based upon replicative limiting dilution analysis and the pragmatic tradeoffs between analytical sensitivity and practical utility.
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  • 30
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 233-236 
    ISSN: 1476-5535
    Keywords: Keywords: Agrobacterium rhizogenes; Agrobacterium tumefaciens; capsule; calcofluor; exopolysaccharide; optical tweezers; rheometry
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    Notes: Comparison of the optical trapping efficiency of Agrobacterium rhizogenes and A. tumefaciens strains indicates the A. rhizogenes strain, ATCC 11325, is significantly less efficiently trapped than A. rhizogenes A4, ATCC 15834, and the A. tumefaciens strain LBA4404. Differences were also found in capsule generation, growth media viscosity, and transmission electron microscopy negative staining. These observations imply a difference in surface structure exists. Calcofluor fluorescence suggests the difference involves an exopolysaccharide.
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  • 31
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 254-259 
    ISSN: 1476-5535
    Keywords: Keywords: atrazine; Biolog; community; biodegradation
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fifteen atrazine-degrading microbial communities obtained from different sources were able to degrade atrazine in a liquid mineral medium as the main organic substrate at high rates (atrazine half-lives ranging from 20 to 164 h). Hydroxyatrazine was the sole metabolite detected. This metabolite was always transient but its maximum level varied from 4 to 67% of the parent compound. Communities originating from subsurface sediments degraded atrazine at similar rates (half-lives between 56 and 62 h). A Biolog characterisation revealed a wide diversity of substrate utilisation by the communities originating either from the surface or the subsurface environments. Twenty-four Biolog carbon sources were degraded by the fifteen communities. A multiple regression analysis established a statistically significant relationship between the atrazine DT50 values of thirteen communities and their responses to four Biolog carbon sources.
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  • 32
    ISSN: 1476-5535
    Keywords: Keywords: yeast growth; sterols; unsaturated fatty acids; oxygen; anaerobiosis; amino acids; purine and pyrimidine bases; Saccharomyces cerevisiae
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    Notes: Nine out of ten industrially important strains of Saccharomyces cerevisiae did not grow in minimal media under anaerobic conditions even when ergosterol and unsaturated fatty acids were provided. Anaerobiosis was maintained either by flushing the culture flasks with prepurified nitrogen or by incubating the flasks in an anaerobic chamber. Traces of oxygen present in ‘prepurified nitrogen gas’ were sufficient to initiate yeast growth and on removal of the oxygen by catalytic means the yeasts failed to grow. The yeast grew very well anaerobically if the medium was supplemented with a mixture of amino acids or with a mixture of purines and pyrimidines. The growth initiated by including a mixture of amino acids was further enhanced when the medium was supplemented with ergosterol and an unsaturated fatty acid. Since no oxygen requirement for the synthesis of amino acids or purines and pyrimidines has been demonstrated, growth promotion by these compounds under anaerobic conditions is most likely not by eliminating the need for oxygen for their synthesis. We suggest that the amino acids and the nucleic acid bases yielded, through some hitherto unknown reactions, small amounts of a molecular or usable form of oxygen which allowed key reactions essential for ‘anaerobic’ growth to proceed.
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  • 33
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 292-295 
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    Keywords: Keywords: castor oil; hydrolysis; lipase; metal ions; Pseudomonas aeruginosa
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    Notes: The ability of an extracellular lipase from Pseudomonas aeruginosa KKA-5 to commence hydrolysis of castor oil in the presence of various metal chlorides, was investigated. Apart from CaCl2 (commonly used for castor oil hydrolysis), AlCl3 (group IIIB), CrCl3 (group VIA) and MgCl2 (group IIA) displayed enhanced hydrolysis capability. Specifically, our statistics show that with respect to time, when Cr3+ was used, hydrolysis of castor oil was four times faster than that of calcium, and 1.6 times faster with regards to Al3+. The chlorides of group VIII and alkali metals had no effect on hydrolysis. Group IV metal chlorides did not enhance lipase activity and inhibited castor oil hydrolysis. The effect of metal ions from other groups on lipase activity is also reported.
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  • 34
    ISSN: 1476-5535
    Keywords: Keywords: activated sludge; biological phosphate removal; polyphosphate; Acinetobacter
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    Notes: The bacterial community of a biological phosphate removal (BPR) activated sludge process was studied and compared to that of a non-BPR process treating the same municipal waste water. Bacterial isolates from the BPR process, as characterized by whole cell fatty acids, belonged to more than twenty genera, with Micrococcus, Staphylococcus and Acidovorax scoring highest. Acinetobacter spp represented 4% of cultured bacteria, ≤3% as estimated by fluorescence in situ hybridization, and well under 10% on the basis of the proportion of ubiquinone Q9 in the sludge. The mole proportions of ubiquinones, Q8 : Q10 : Q9 in the sludge were maintained fairly stable at approximately 9:4:1. The spectra of the isolated strains and the proportions of ubiquinones in the processes (BPR vs non-BPR) were otherwise similar, but a significant number of isolates related to actinomycetes were obtained from the BPR sludge only. The BPR process did not enrich Acinetobacter. Pure cultures of Acinetobacter isolated from the sludge stained for polyphosphate, but Acinetobacter cells responding to the ACA probe in native sludge from the BPR process did not. Instead, the bulk of the polyphosphate in the BPR sludge was located in a distinct morphotype of large, coccoid, highly clustered cells.
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  • 35
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 307-310 
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    Keywords: Keywords: yeast; cane molasses; ethanol; tamarind
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Tamarind wastes such as tamarind husk, pulp, seeds, fruit and the effluent generated during tartaric acid extraction were used as supplements to evaluate their effects on alcohol production from cane molasses using yeast cultures. Small amounts of these additives enhanced the rate of ethanol production in batch fermentations. Tamarind fruit increased ethanol production (9.7%, w/v) from 22.5% reducing sugars of molasses as compared to 6.5% (w/v) in control experiments lacking supplements after 72 h of fermentation. In general, the addition of tamarind supplements to the fermentation medium showed more than 40% improvement in ethanol production using higher cane molasses sugar concentrations. The direct fermentation of aqueous tamarind effluent also yielded 3.25% (w/v) ethanol, suggesting its possible use as a diluent in molasses fermentations. This is the first report, to our knowledge, in which tamarind-based waste products were used in ethanol production.
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  • 36
    ISSN: 1476-5535
    Keywords: Keywords: pentachlorophenol; biodegradation; growth physiology; cultivation; Mycobacterium chlorophenolicum PCP-1; Sphingomonas chlorophenolica RA2
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    Notes: The physiological characteristics of growth and pentachlorophenol degradation of the bacteria Sphingomonas chlorophenolica RA2 and Mycobacterium chlorophenolicum PCP-1 were studied quantitatively in liquid culture under various conditions of pH, temperature, pO2, pCO2 and PCP concentration. Concerning their metabolic properties, RA2 and PCP-1 can be regarded as r-strategist and K-strategist, respectively. RA2 showed a higher activity concerning growth and PCP degradation than PCP-1 under optimum conditions. However, PCP-1 performed better under extreme conditions. Maximum growth rates or RA2 and PCP-1 on glucose were 0.21 h−1 and 0.024 h−1 and maximum PCP degradation rates 315 and 40 μmol (g of dry cells)−1 h−1, respectively. Optimized cultivation for RA2 on a technical scale led to the production of 40 g L−1 of cell dry mass within 55 h. The cultivation strategy including pH-controlled ammonium feeding can be used to effectively produce sufficient biomass of both strains for both research and application as inoculants in soil clean-up.
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  • 37
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 309-316 
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    Keywords: Keywords: biosynthesis; immunosuppressants; prolylrapamycin; rapamycin; Streptomyces hygroscopicus
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    Notes: A trace of prolylrapamycin is often produced in rapamycin fermentations carried out by strains of Streptomyces hygroscopicus. Prolylrapamycin was produced as the major rapamycin when L-proline was added to the fermentation medium. Addition of proline plus thiazolidine-2-carboxylic acid (T2CA), a sulfur-containing proline analog, prevented rapamycin production and stimulated prolylrapamycin production, thereby resulting in an even greater selective production of prolylrapamycin. T2CA addition inhibited rapamycin production even in the presence of L-lysine which is converted into pipecolic acid intracellularly and normally stimulates rapamycin formation. Addition of the rapamycin precursor, DL-pipecolic acid, surprisingly failed to stimulate rapamycin production. However, when DL-pipecolic acid was added with L-proline, it reduced the formation of prolylrapamycin and stimulated rapamycin production; this was evident especially in the presence of T2CA. The evidence suggests that T2CA suppresses rapamycin production by inhibiting intracellular conversion of L-lysine into pipecolate. Furthermore, the data suggest that uptake of pipecolate into the cell is stimulated or induced by growth in the presence of L-proline and/or T2CA.
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  • 38
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 354-359 
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    Keywords: Keywords: fluidized bed; drinking water; post treatment; dentrification; bacterial regrowth
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    Notes: Post treatment of effluents from heterotrophic groundwater denitrification fluidized bed reactors (FBR) designed to achieve drinking water quality has been investigated. The denitrification process adds to the dissolved organic compounds, biomass and bacteria in the effluent. They are also lacking dissolved oxygen. Effluents from the process were treated in combined post treatment processes based on either a trickling filter and sedimentation unit (‘TF combination’) or contact flocculation (‘CF combination’). Both processes were followed by sand filtration, granular activated carbon (GAC) and chlorination. Results regarding total suspended solids (TSS) and turbidity removal showed an advantage to the ‘CF combination’, and the target turbidity (NTU 〈1) was always achieved when the alum dose was 10 or 20 mg l−1. Backwash of the sand filter and GAC column was required after 27 h of operation (average value). An average total reduction in dissolved organic carbon (DOC) of 40% was observed with a final DOC of 3.5–4 mg L−1. Most of the removal of the DOC occurred in the sand filter (28%), while the GAC contribution was smaller (18%). No regrowth potential was observed using the Werner method when a pure culture of Pseudomonas fluorescens P17 was used as inoculum in samples of chlorinated effluent (post chlorination). When a mixed culture of indigenous bacteria was used as inoculum, a high regrowth potential was observed. Installing an additional chlorination unit before the sand filter column (pre and post chlorination) resulted in effluent with no regrowth potential for both Pseudomonas fluorescens P17 and indigenous bacteria.
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  • 39
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 369-372 
    ISSN: 1476-5535
    Keywords: Keywords: biodegradation; soybean hulls; petrochemical oxidation
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Respirometer studies were used to determine the benefits of mixing soybean hulls with gravel contaminated with petroleum products. The aerobic conditions prevailing in the respirometer maintained significant microbiological activity. A reduction in petrochemical concentrations was detected, whether the contaminated gravel was treated with agricultural by-products or not, but at a slightly faster rate with the treatment.
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  • 40
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 28-30 
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    Keywords: Keywords: indicator bacteria; coliphages; Boston Harbor; birds; pigeon; herring gull; Canada geese
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    Notes: Droppings from feral populations of pigeons, geese and herring gulls from the urban/suburban environment around Boston Harbor, MA, USA contained up to 106 somatic coliphages, 108 enterococci, 109 thermotolerant coliforms and 102 F-specific coliphages per gram of feces. Somatic coliphages, enterococci and thermotolerant coliforms were common in the feces of all three kinds of birds but F-specific coliphages were found in droppings from only three of 32 gulls. Thus these sources of bacterial and viral indicators should be considered when dealing with the ecology of fecal pollution indicators. Moreover, microbial indicators of fecal or sewage pollution originating from bird droppings may be mistaken for indicators that come from humans. This may cause an overestimate of the hazard from human pathogens in water and confound attempts to locate sources of fecal or sewage pollution.
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  • 41
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 22-27 
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    Keywords: Keywords: sucrose; isomaltulose; trehalulose; isomaltulose synthase; Klebsiella planticola
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    Notes: An isomaltulose-producing bacterium was isolated and taxonomically characterized. Its morphological and biochemical properties conform best to those described for Klebsiella planticola. When cultured under optimal conditions, the organism simultaneously converted sucrose into both isomaltulose (α-D-glucopyranosyl-1,6-fructose) and trehalulose (α-D-glucopyranosyl-1,1-fructose) with substrate conversion rates of 80% and 15%, respectively. Sucrose and Bacto-tryptone were the most effective carbon and supplemental nitrogen sources, respectively, for producing cells of high isomaltulose-forming ability. None of several inorganic salts tested had any significant effect. The major product formed in the reaction mixture was verified to be isomaltulose by co-chromatography and IR spectroscopy.
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  • 42
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    Keywords: Keywords: dextransucrase; Leuconostoc mesenteroides; pulque; glucosyltransferase
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    Notes: Dextransucrase was produced from a Leuconostoc mesenteroides isolated from pulque, a traditional Aztec alcoholic beverage produced from agave juice containing sucrose as the main carbon source. Almost all the dextransucrase activity (87%) was associated with the cells, and was unusually high (1.04 U mg−1 of cells). The culture medium composition was optimized through a Box-Behnken method resulting in a process yielding 2.2 U ml−1 of insoluble glucosyltransferase activity. The enzyme had a molecular weight of 166 kDa. Optimal temperature was 35°C with a half-life of 137 min at the same temperature. As with dextransucrase from the industrial strain L. mesenteroides NRRL B-512F, the enzyme showed Michaelis–Menten kinetic behavior with excess substrate inhibition (K m and K i values of 0.026 M and 1.23 M respectively); produced soluble linear dextran with glucose molecules linked mainly in α(1–6) with branching in α(1–3) in a proportion of 4:1 as shown by NMR studies; and produced a high yield of isomalto-oligosaccharides in the presence of maltose.
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  • 43
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 65-74 
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    Keywords: Keywords: acid-base response; bacterial suspensions; chemoheterotrophic bacteria
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The response of suspensions of non-proliferating bacteria to external pH ranging from 3.6 to 9.9 was examined. The acid-base response is affected by the number of viable cells in the suspensions and culture conditions (aerobiosis or anaerobiosis) but not by culture time, composition of the culture medium or the age of suspensions. The results with carbonylcyanide m-chlorophenylhydrazone-and N, N′- dicyclohexylcarbodiimide-treated cells indicated that passive proton conductance and proton translocation by ATP could be involved in this response. pH profiles of suspensions of 18 chemoheterotrophic Gram-negative and Gram-positive bacteria support the hypothesis that the proton gradient generated by an alkali or an acid shift could be dissipated by bacteria with respiratory metabolism.
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  • 44
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 99-114 
    ISSN: 1476-5535
    Keywords: Keywords: AFLP; molecular markers; genetic mapping; PCR; polymorphism; DNA fingerprinting
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    Notes: Amplified fragment length polymorphism (AFLP) is a novel molecular fingerprinting technique that can be applied to DNAs of any source or complexity. Total genomic DNA is digested using two restriction enzymes. Double-stranded nucleotide adapters are ligated to the DNA fragments to serve as primer binding sites for PCR amplification. Primers complementary to the adapter and restriction site sequence, with additional nucleotides at the 3′-end, are used as selective agents to amplify a subset of ligated fragments. Polymorphisms are identified by the presence or absence of DNA fragments following analysis on polyacrylamide gels. This technique has been extensively used with plant DNA for the development of high-resolution genetic maps and for the positional cloning of genes of interest. However, its application is rapidly expanding in bacteria and higher eukaryotes for determining genetic relationships and for epidemiological typing. This review describes the AFLP procedure, and recent, novel applications in the molecular fingerprinting of DNA from both eukaryotic and prokaryotic organisms.
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  • 45
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 145-149 
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    Keywords: Keywords: Clostridium thermocellum; acetate kinase; phosphotransacetylase; thermophilic bacteria; PCR; gene cloning
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    Notes: Cloning of Clostridium thermocellum acetate kinase (ack) and/or phosphotransacetylase (pta) genes in Escherichia coli by functional complementation of ack and/or pta mutants was complicated by an alternative acetate assimilation pathway involving acetyl-CoA synthetase (ACS). In addition to the problems encountered with the complementation approach, cloning of these genes was not readily achieved using heterologous probing with corresponding genes from Escherichia coli and Methanosarcina thermophila due to the lack of sufficient homology. The use of a PCR-based approach, on the other hand, yielded a specific C. thermocellum gene fragment which showed significant sequence identity to the ack gene for which primers were designed. The subcloned ack fragment was then successfully used as a probe for the isolation of the corresponding gene and restriction analysis of that region.
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  • 46
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 91-91 
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  • 47
    ISSN: 1476-5535
    Keywords: Keywords: Listeria monocytogenes; dairy products; PCR; fluorogenic; detection
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    Notes: The presence of Listeria monocytogenes as a dairy food contaminant is a lethal threat to dairy industrialists; therefore, products tainted with L. monocytogenes must be quickly detected and removed from production. This fluorogenic PCR-based assay was developed to rapidly detect L. monocytogenes contamination in dairy samples before a final product is distributed. The detection method employed uses a PCR primer pair and a fluorogenic TaqMan probe which bind to a region of a virulence determinant gene specific to L. monocytogenes. As the DNA target is amplified, the 5′ nuclease activity of Taq DNA polymerase hydrolyzes the internal fluorogenic probe creating a change in fluorescence that can be monitored and automatically analyzed with a fluorometer. Sensitivity studies indicated a lower detection limit of under 10 CFU for pure culture extracts and spiked dairy enrichments. A study was performed on 266 dairy product samples obtained from Central California dairy production plants. Eighty-three of these samples were artificially spiked with both high and low concentrations of L. monocytogenes before an overnight enrichment in TSB/LiCl/colostin sulfate/moxalactam media. DNA from enriched samples was obtained using a rapid Chelex extraction specifically designed for dairy sample enrichments and automated analysis. The extraction was followed by the fluorogenic PCR assay and measurement of fluorescence increase. The assay was completed within 24 h, with an observed 95.2% sensitivity, 96.7% specificity, 92.9% positive predictive value, 97.8% negative predictive value, and 96.2% accuracy. According to specificity studies, five other bacterial species cross-reacted with the fluorogenic 5′ nuclease PCR. However, only one of these strains (Listeria grayi) was able to grow in the enrichment medium employed, and was not isolated from any of the 266 dairy product enrichments evaluated in this study. Therefore, this method provides a rapid, sensitive, and automatable analysis alternative to standard culture techniques for the detection of Listeria monocytogenes in dairy samples.
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  • 48
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 192-202 
    ISSN: 1476-5535
    Keywords: Keywords: compactin; Penicllium cyclopium; antihypercholesteremic agent; bioreactor for compactin; continuous synthesis
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Compactin was synthesized by Penicillium cyclopium in submerged as well as in bioreactor systems and assayed spectrophotometrically with a detection limit of 0.5 μg ml−1 solvent. Synthesis in submerged culture was affected by aeration, glucose level, pH, and type and molarity of buffer. Citrate or succinate (pH 4.0, 0.10 M) in malt glucose peptone broth (MGPB) stimulated cell specialization, sporulation, enhanced compactin permeation from mycelia and its production (60.05 μg ml−1 after 12 days). Fungal spores, immobilized onto-into loofah sponge, in a bioreactor, using MGPB-citrate as feed stock, resulted in productivity of 23.04 mg compactin (L−1 h−1) during 50 days operation at 0.45 h−1 dilution rate. Compactin synthesis in the bioreactor was also affected by culture age, substrate, incubation and dilution rates. Scanning electron micrographs of the loofah sponge, prior to, during and post-spores immobilization showed that loofah channels served well for fungal support in the bioreactor.
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  • 49
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 228-232 
    ISSN: 1476-5535
    Keywords: Keywords: Phaffia rhodozyma; ploidy; yeast; astaxanthin
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ploidy of the red yeast Phaffia rhodozyma was evaluated using flow cytometric analyses of propidium iodide- stained cells and mutagenic inactivation kinetics. Our findings suggest that Phaffia rhodozyma is not haploid. Auxotrophic strains were generated at a high frequency following treatment of mutagenized cells with a combination of benomyl and ethyl acetate. Studies of an auxotrophic mutant using flow cytometry and UV inactivation indicated possible chromosome loss to an aneuploid state.
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  • 50
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 219-224 
    ISSN: 1476-5535
    Keywords: Keywords: electroporation; Saccharopolyspora erythraea; homologous recombination; propionyl-CoA carboxylase
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The introduction of plasmid DNA into germinating spores of an industrially improved strain of Saccharopolyspora erythraea was accomplished by electroporation. Various parameters affecting the efficiency of electroporation were examined. The most critical factor was the extent of spore germination. Electrocompetence was limited to a 4-h period following the initial emergence of the germ tube. Electroporation efficiencies as high as 2 × 105 CFU μg−1 of plasmid DNA were obtained using electrocompetent germlings. The optimal field strength was 12–14 kV cm−1 with a pulse duration of 15–20 ms. Electrocompetent germlings were stored at −80°C without a significant decrease in transformation efficiency. The utility of this protocol was demonstrated by isolating a propionyl-CoA carboxylase mutant through targeted gene disruption and replacement.
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  • 51
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 237-241 
    ISSN: 1476-5535
    Keywords: Keywords: bacterial bioherbicide; freeze drying; growth phase; liquid culture production; shelf life; biological control
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Xanthomonas campestris MB245, a specific pathogen of the weedy grass Poa annua (annual bluegrass), is being developed as a bioherbicide to control this pest in turf. Nutritional and environmental factors were evaluated based on their ability to support rapid submerged culture growth and high cell yield. Temperature optima for the growth of X. campestris cells in submerged culture were between 27 and 30°C. At 30°C, optimal nutritional conditions for X. campestris growth supported generation times of 150–175 min and cell yields after 24 h growth of 1–2 × 1010 cells ml−1. Media containing sucrose or glucose as the carbon source and various organic nitrogen sources supported optimal X. campestris growth and cell yield. The addition of vitamin mixtures to complex and defined media had no significant effect on growth or cell yield. The age of X. campestris cultures had a significant impact on cell survival after freeze drying. Following freeze drying, log phase cell survival (44%) was significantly lower than early and late stationary phase cell survival, 62% and 68%, respectively. Cells harvested in stationary phase, freeze dried and stored under vacuum at 4°C, showed no significant loss in viability after 6 months. Thus, high cell concentrations of the bioherbicide X. campestris can be rapidly produced in submerged culture and stabilized as freeze-dried preparations.
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  • 52
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 283-288 
    ISSN: 1476-5535
    Keywords: Keywords: Spirulina platensis; mixotrophic culture; light irradiance; phycocyanin production; kinetic model
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phycocyanin production by high cell density cultivation of Spirulina platensis in batch and fed-batch modes in 3.7-L bioreactors with a programmed stepwise increase in light intensity program was investigated. The results showed that the cell density in fed-batch culture (10.2 g L−1) was 4.29-fold that in batch culture (2.38 g L−1), and the total phycocyanin production in the fed-batch culture (0.795 g L−1) was 3.05-fold that in the batch culture (0.261 g L−1). An unstructured kinetic model to describe the microalga culture system including cell growth, phycocyanin formation, as well as glucose consumption was proposed. The data fitted the models well (r 2 〉 0.99). Furthermore, based on the kinetic models, the potential effects of light limitation and photoinhibition on cell growth and phycocyanin formation can be examined in depth. The models demonstrated that the optimal light intensity for mixotrophic growth of Spirulina platensis in batch or fed-batch cultures using a 3.7-L bioreactor was 80160 μE m−2 s−1, and the stepwise increase in light intensity can be replaced by a constant light intensity mode.
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  • 53
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 296-299 
    ISSN: 1476-5535
    Keywords: Keywords: D-aminoacylase; Stenotrophomonas maltophilia; Xanthomonas maltophilia; Alcaligenes sp
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    Notes: A novel bacterial strain producing D-aminoacylase was isolated from organic waste and identified as Stenotrophomonas maltophilia ITV-0595. The isolation was performed using N-acetyl-D-phenylglycine (NAcDPG) as the sole source of C and N. The optimum pH for enzyme expression was 8 at 37°C. Using N-Ac-DPG concentrations from 0.5 up to 3% w/v, it was observed that at the 1% level, the microorganism showed acceptable responses in both enzyme activities and cell growth. From the different tested compounds N-acetyl-D-methionine (1%) was the best enzyme inducer (Sp. act. = 4.14 U mg−1 protein, Vol. act. = 0.17 U ml−1) and the only one that increased cell growth.
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  • 54
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 311-314 
    ISSN: 1476-5535
    Keywords: Keywords: beta-lactam production; P. chrysogenum; S. pombe; malachite green; protoplasts
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We attempted protoplast fusion in order to generate gene transfer between an industrial strain of Penicillium chrysogenum and a fission yeast, Schizosaccharomyces pombe. The Penicillium strain was treated with malachite green. The S. pombe strain was auxotrophic for lysine. The regenerated colonies showed Penicillium morphology. The number of Penicillium colonies was significantly higher when the inactivated Penicillium protoplasts were fused to S. pombe protoplasts than in the self-fusion control experiments. We randomly isolated colonies from the regeneration plates and measured beta-lactam formation in cultures from shaken flasks. Antibiotic production was increased in colonies originated from the malachite green-treated protoplasts.
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  • 55
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 360-363 
    ISSN: 1476-5535
    Keywords: Keywords: chemical mutagenesis; gene duplication; insertional cloning; transposon mutagenesis; linear replicon fusion
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The most potent chemical mutagens commonly used for yield enhancement in streptomycetes induce a limited spectrum of base-pair substitutions, heavily dominated by GC to AT transitions. The AT to CG transversion pathway complements the GC to AT pathway, but no strong mutagens with this specificity are available. However, mutT mutations in Escherichia coli enhance spontaneous AT to CG transversions about 1000-fold, so such mutations in streptomycetes could be very beneficial for random mutagenesis. Rate-limiting steps in secondary metabolite biosynthesis, on the other hand, can be best addressed by cloning and insertion of extra copies of the appropriate gene(s) into a neutral genomic site. This approach has been used successfully to improve the production of tylosin and pristinomycin. Transposon mutagenesis can be used to identify and clone neutral genomic sites, as demonstrated in Streptomyces fradiae to improve tylosin yields. Transposon mutagenesis can also be used to activate or enhance the transcription of genes important for secondary metabolite production, and to identify and clone both positive and negative regulatory elements. In some cases it may be advantageous to amplify the complete biosynthetic pathway for secondary metabolite production. In Streptomyces rimosus, a highly productive oxytetracycline producer was shown to contain the complete biosynthetic pathway near the end of the linear chromosome, and on a hybrid linear plasmid that had undergone recombination with the chromosome. This concept of linear replicon fusion might be applicable to other secondary metabolite pathway genes that are located near one end of the linear chromosome.
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  • 56
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 376-376 
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  • 57
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    Journal of industrial microbiology and biotechnology 20 (1998), S. 364-368 
    ISSN: 1476-5535
    Keywords: Keywords: lignocellulosic biomass; prehydrolysate; Pichia stipitis; aromatic; inhibitors
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differences in the relative toxicity of xylose-rich prehydrolysates derived from woody and herbaceous feedstocks are likely due to the relative abundance of a variety of inhibitory compounds. Acetate, as well as several aromatic monomers, has been shown to be an inhibitor of the xylose-fermenting yeast, Pichia stipitis. Comparative information on the concentration of known and likely inhibitors, other than acetate, is lacking. The present study provides data on the aromatic monomer composition of representative herbaceous and woody prehydrolysates. Dilute-acid prehydrolysates were prepared from three feedstocks; two herbaceous, corn stover and switchgrass (Panicum virgatum L.), and one woody (poplar). The prehydrolysates were neutralized with Ca(OH)2 extracted with ethyl acetate, trimethylsilylated, and analyzed by GC-MS. Fourteen aromatic monomers were tentatively identified by comparison with published mass spectra. The concentrations of the aromatic monomers totalled 112, 141 and 247 mg L−1 for corn stover, switchgrass and poplar prehydrolysates, respectively. This is also the order of increasing inhibition of growth and ethanol productivity observed for Pichia fermentations. The woody prehydrolysate contained approximately four-fold more syringyl-based monomers than did the herbaceous prehydrolysates, while guaiacyl-containing compounds were more evenly distributed.
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  • 58
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 81-90 
    ISSN: 1476-5535
    Keywords: Keywords: nigericin; geldanamycin; guanidylfungin A; chitinase; β-1,3-glucanase; Streptomyces violaceusniger; biocontrol
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    Notes: Streptomyces violaceusniger strain YCED-9 is an antifungal biocontrol agent antagonistic to many different classes of plant pathogenic fungi. We discovered that strain YCED-9 produces three antimicrobial compounds with antifungal activity. These compounds were purified and identified, and included: AFA (Anti-Fusarium Activity), a fungicidal complex of polyene-like compounds similar to guanidylfungin A and active against most fungi except oomycetes; nigericin, a fungistatic polyether; and geldanamycin, a benzoquinoid polyketide highly inhibitory of mycelial growth of Pythium and Phytophthora spp. Antimicrobial assays were developed to estimate the production of each antibiotic independently. Medium composition had differential effects on the production of each metabolite. The hydrolytic enzymes chitinase and β-1,3-glucanase are also produced under induction by colloidal chitin and laminarin, respectively. Fungal cell walls induced the production of both enzymes. A potential for biological control of diseases caused by P. infestans was also suggested by strain YCED-9’s strong in vitro antagonism towards pathogenic isolates of this fungus.
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  • 59
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 11-18 
    ISSN: 1476-5535
    Keywords: Keywords: biodegradation; BTEX; microbial kinetics, respirometry
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biodegradation of BTEX by a microbial consortium isolated from a closed municipal landfill was studied using respirometric techniques. The kinetics of biodegradation were estimated from experimental oxygen uptake data using a nonlinear parameter estimation technique. All of the six compounds were rapidly degraded by the microbial culture and no substrate inhibition was observed at the concentration levels examined (200 mg L−1 as COD). Microbial growth and contaminant degradation were adequately described by the Monod equation. Considerable differences were observed in the rates of BTEX biodegradation as seen from the estimates of the kinetic parameters. A three-fold variation was seen in the values of the maximum specific growth rate, μmax. The highest value of μmax was 0.389 h−1 for p-xylene while o-xylene was characterized by a μmax value of 0.14 h−1, the lowest observed in this study. The half saturation coefficient, K s, and the yield coefficient, Y, varied between 1.288–4.681 mg L−1 and 0.272–0.645 mg mg−1, respectively. Benzene and o-xylene exhibited higher resistance to biodegradation while toluene and p-xylene were rapidly degraded. Ethylbenzene and m-xylene were degraded at intermediate rates. In biodegradation experiments with a multiple substrate matrix, substrate depletion was slower than in single substrate experiments, suggesting an inhibitory nature of substrate interaction.
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  • 60
    ISSN: 1476-5535
    Keywords: Keywords: hEGF; plasmid pSLT; ytl2-incR stabilization
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A plasmid stabilization system, active in high copy-number plasmids, was cloned from the large resident plasmid, pSLT, of Salmonella typhimurium. The ytl2 gene, together with a 249-bp region (termed incR) downstream of the gene, imparted 〉104-fold stability to a pBR322-based plasmid. The ytl2-incR region was then used to stabilize a recombinant plasmid carrying the human epidermal growth factor gene (with the Escherichia coli K-12 ompA signal sequence), behind the lacUV5 promoter. In shake flask tests to optimize expression of human epidermal growth factor, loss of recombinant plasmid was 〈1% when growth (both before and after induction with isopropyl-β-d-galactopyranoside) took place even in the absence of antibiotic selection, and the specific activity of secreted human epidermal growth factor was ca 20 μg per 108 cells at harvest, compared to a figure of ca 3 μg per 108 cells when a comparable plasmid, but devoid of the ytl2-incR region, was employed, as outgrowth of plasmid-free cells after induction severely compromised the specific activity of the secreted product.
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  • 61
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 57-64 
    ISSN: 1476-5535
    Keywords: Keywords: glucose 2-oxidase; lignin degradation; one-step purification; glucose 1-oxidase; basidiomycete fungi; immobilized metal affinity chromatography
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose 2-oxidase (EC 1.1.3.10) from Coriolus versicolor and Phanerochaete chrysosporium and glucose 1-oxidase (EC 1.1.3.4) from Aspergillus niger bound to a CU(II)-IDA column in the pH range of 6–8. However, glucose 1-oxidase from Penicillium amagasakiense bound only partially to a CU(II)-IDA column at pH 8.0. Metal chelates containing either Ni(II) or Zn(II) were useful in the adsorption of glucose 2-oxidase from Phanerochaete chrysosporium. The binding of glucose 2-oxidase from P. chrysosporium to Ni(II) and Zn(II)-IDA agarose columns increases as a function of pH of the buffer system. The adsorption of glucose oxidases on metal(II)-IDA chelates was due to the available histidine residues on enzyme molecules since the addition of imidazole in the buffer system abolished the binding of glucose oxidases to these columns. Both glucose oxidases from C.versicolor, P. chrysosporium and A. niger were purified in one step by immobilized metal affinity chromatography on metal(II)-IDA agarose columns with a recovery of enzyme activity in the range of 80–91%. Purified preparations of glucose oxidases from fungal strains were apparently homogeneous on native PAGE and SDS-PAGE. Immobilized metal affinity chromatography was used to separate glucose 1-oxidase from the 2-oxidase on metal(II)-IDA agarose columns which was confirmed by analysis of the reaction products by HPLC. The different chromatographic behaviour of glucose oxidases on metal(II)-IDA chelates is apparently due to the number and spatial distribution of available histidine residues on these enzyme molecules.
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  • 62
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 115-120 
    ISSN: 1476-5535
    Keywords: Keywords: species identification; DNA isolation; meat testing; satellite DNA
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A convenient DNA-based identification system is described for testing the species origin of meat samples. Probes are generated by PCR with primers binding to species-specific satellite DNA and hybridized to DNA purified from meat. This method is more robust and versatile than methods based on oligonucleotide hybridization. With the exception of a slight cross-reaction of mutton and beef, each probe only recognized the species from which it was derived. Purifying the DNA with a DNA-binding resin improved the sensitivity. Admixtures of 0.1–0.5% can be detected in raw meat and 0.5–5% in autoclaved meat samples. The method can be adapted to detect any eukaryotic species for which species-specific DNA sequences are available. This method has proven its value in the routine inspection of meat samples by revealing more cases of deliberate or accidental species substitution and admixture than conventional techniques.
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  • 63
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 178-183 
    ISSN: 1476-5535
    Keywords: Keywords: carboxymethyl cellulase; intergeneric fusants; pH and thermal stability; response surface methodology
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The combined effect of pH and temperature on carboxymethyl cellulase from two intergeneric fusants (M 14 and M 62) of Trichoderma reesei QM 9414/Saccharomyces cerevisiae NCIM 3288 was studied using response surface methodology. A central composite design for two variables was employed for the optimization studies. This study was compared with similar studies carried out with Trichoderma reesei QM 9414. The optimal pH and temperature for the enzymes derived from these organisms were: for the fusant M 14—pH 5.7 and 41.7°C, for the fusant M 62—pH 5.3 and 43°C, and for Trichoderma reesei QM 9414—pH 4.31 and 38.3°C.
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  • 64
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 184-186 
    ISSN: 1476-5535
    Keywords: Keywords: neutralization; triclosan
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    Notes: A variety of bactericidal tests are available for evaluating the antimicrobial activity of products. An often overlooked variable in these types of studies is adequate neutralization. Triclosan is a widely used antimicrobial agent and has been shown to be difficult to neutralize. Incomplete neutralization may overestimate the efficacy of triclosan-containing products.
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  • 65
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 203-207 
    ISSN: 1476-5535
    Keywords: Keywords: fermentation; vegetable oils; tetracycline; Streptomyces aureofaciens
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    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To evaluate their potential to enhance fermentation performance, vegetable oils were investigated in a model tetracycline fermentation. With sucrose as the carbon source, the fermentation efficiency of Streptomyces aureofaciens (ATCC 10762) was enhanced by the inclusion in the medium of low levels of vegetable oil. Soybean and sunflower oils significantly improved the rate of sucrose consumption and tetracycline production suggesting that oil is an excellent adjuvant for improving fermentation productivity. For optimum benefit, the dosage level was critical. Little difference was observed between crude and refined oils. These data contribute to the assessment of industrially available fermentation feedstocks, and to the development of new feedstock products for specific fermentation applications.
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  • 66
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 215-218 
    ISSN: 1476-5535
    Keywords: Keywords: model; temperature; growth rate; dimensionless
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    Notes: The influence of sub-optimal temperatures (T) on the microbial growth rate (μ) has been assessed by means of dimensionless variables: Tdim = [T−Tmin]/[Topt−Tmin] and μdim = μ/μopt. Tmin represents the temperature at which there is no growth, Topt the optimum temperature at which the growth rate, μopt, is maximum. Data sets, growth rate vs temperature, have been taken from the literature for 12 organisms (psychrotrophs, mesophiles and thermophiles). In order to compare these organisms, the power law function has been used: [μdim] = [Tdim]α. The parameters μopt and Topt are determined from direct readings whereas Tmin and αare estimated by means of a non-linear regression. An accurate estimation of Tmin is obtained providing low growth rate data are available. A wide range of optimal temperatures where the growth rate almost equals μopt prevents one from obtaining a narrow confidence interval forα. On the basis of the analysis hereafter developed, thermophiles are characterized by values of the power α less than mesophiles and psychrotrophs. Almost all of these values are significantly different from two, previously determined for Staphylococcus xylosus and widely used for predicting the microbial growth in foods.
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    Journal of industrial microbiology and biotechnology 21 (1998), S. 332-333 
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  • 68
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present work deals with copolymerization of styrene (STY) and methyl methacrylate (MMA) catalysed by nickel acetylacetonate - Ni(acac) 2 , employing methylaluminoxane (MAO) as cocatalyst. This catalyst system presented low catalyst activities for STY homopolymerization and very high activities for MMA. It seems that the catalyst system based on Ni(acac) 2 /MAO is effective for the copolymerization of MMA and STY to give block copolymer but it also produced polystyrene and poly(methyl methacrylate) homopolymers. The polymers were characterized by 13 C NMR, GPC and FTIR. The polystyrene homopolymer was identified by IR and NMR analyses of the cyclohexane soluble fraction. The presence of absorption bands correspondent to carbonyl group and aromatic ring was observed in the IR spectrum of the acetic acid soluble part. This result is a clue that STY-MMA copolymer with low molecular weight was produced. The high molecular weight copolymer (acetic acid insoluble fraction) was also characterized by IR analysis which indicated the presence of characteristic absorption bands of carbonyl group and aromatic ring. These results were confirmed by 13 C NMR analysis.
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  • 69
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    Polymer bulletin 40 (1998), S. 555-562 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Four narrow-distribution samples of sodium hyaluronate with weight-average molecular weights M w of 3.8 × 103 to 1.1 × 104 in 0.02 and 0.1 M aqueous NaCl at 25°C have been studied by small-angle X-ray scattering. Data for their z-average radii of gyration 〈S2〉z 1/2 and particle scattering functions P(θ), together with previous 〈S2〉z data from light scattering for high molecular weights, are compared with relevant theories for the wormlike chain with or without excluded volume, using the parameters estimated previously from intrinsic viscosity ([η]) data. It is shown that for M w lower than 1.1 × 104, 〈S2〉z, P(θ), and [η] of the polysaccharide in the aqueous salts are all consistently explained by this model without excluded volume.
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  • 70
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Three new side chain liquid crystalline polythiiranes were prepared with new substituants on the mesogenic groups. Their thermotropic liquid crystalline behaviour was studied by the usual techniques (DSC, X-ray diffraction and polarized optical microscopy). Unlike the polyoxiranes described in the literature, the size of the terminal group has no influence on the nature of the mesophases of polythiiranes ; only slight changes of the transition temperatures were observed. In this series of polymers, a phase, denoted X, appeared at temperatures below the smectic E phase, and could not be identified by usual characterization techniques. An isothermal kinetic study for the smectic E / X phase transition resulted in an Avrami exponent close to 1, suggesting a one-dimensional ordering occurred during the transformation from the smectic phase. This result, combined with other observations, helped us to assign the X phase to the crystalline phase.
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  • 71
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    Polymer bulletin 40 (1998), S. 583-590 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hybrid materials from Polyvinyl chloride (PVC) and titania were prepared using sol-gel technique. In-situ generation of titania network in the PVC matrix was carried out by introducing required amounts of tetrapropylorthotitanate (TPOT) followed by hydrolysis/condensation of TPOT in the matrix. Homogeneous and semi-transparent films were obtained by casting and solvent evaporation. Mechanical properties of these films up to 15 wt. % titania contents were studied. The results showed an increase in the Young's modulus, length at rupture and toughness of the unplasticised PVC. However, the tensile strength and stress at break point decreased with the addition of titania contents. Thermal stability of the material was studied using dehydrochlorination (DHCl) technique and thermogravimetric analysis. The PVC samples with small amount of titania were found to be more stable as compared with the pure PVC.
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  • 72
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY The sorption characteristics of benzene and cyclohexane vapours in the poly(urethane-urea) (PUU) with well defined structure were measured using an improved version of the Mc Bain's microbalance. The diffusion coefficients were calculated for the different vapour activities from the kinetics of solvent uptake, i.e. the sorption isotherms over time. Sorption and diffusion coefficients measured, showed a strong dependence of the applied vapour activity. The obtained transport parameters were discussed with regard to the polymer structure. Based on the sorption and diffusion data, the pervaporation performance of the PUU-based membrane in separation of the benzene/cyclohexane mixtures was predicted and compared with the experimental pervaporation characteristic.
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  • 73
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
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  • 74
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    Polymer bulletin 40 (1998), S. 701-706 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl3, DMF, and DMSO. The structure of the polymer was confirmed by 1H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex.
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  • 75
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    Polymer bulletin 40 (1998), S. 715-720 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Synthesis and polymerization behavior of 1-trimethylsiloxy- or 1-triphenylsiloxy-silacyclobutane derivatives were studied. These monomers gave polymers with reasonably high molecular weight by platinum catalyst like platinum 1,3-divinyl-1,1,3,3-tetramethyldisfloxane complex. Side-chain smectic, liquid crystalline polymer was obtained from 1-methyl-1-[3-{(4-cyanobiphenyl-4'-yl)oxy}propyl]dimethylsiloxysilacyclobutane. In the polymerization by butyllithium or phenyllithium, monomers corresponding to the amounts of the initiator were consumed, but no polymers were formed. Apparently, elimination of the trimethylsiloxy or triphenylsiloxy group occurred in the nucleophilic attack of the initiator or propagating species on the silicon atom of the monomer.
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  • 76
    ISSN: 1436-2449
    Keywords: (Keywords: lanthanocene; methylaluminoxane; polymerization; butadiene; isoprene; styrene.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of butadiene(Bd), isoprene(Ip) and styrene(St) has been examined using the six catalyst systems composed of lanthanocene, (C5H9Cp)2NdCl(I), (C5H9Cp)2SmCl(II), (MeCp)2Sm OAr'(III), (Ind)2NdCl(IV), Me2Si(Ind)2NdCl(V) and (Flu)2NdCl(VI), and methylaluminoxane(MAO) respectively. All of them can be used to form the polyisoprene with molecular weights of 1 to 10 thousand and cis-1,4-unit contents of 41 to 47%. (I), (II) and (III) of them can be also used to form the polybutadiene with molecular weights of 10 to 20 thousand and cis-1,4-unit contents of 62 to 78%. In addition, the catalysts from (II) to (V) are still active for St polymerization and (II) of them gives a syndio -rich random polystyrene. It is noteworthy that (II) and (III) are active for homopolymerization of Bd, Ip and St in the same polymerization condition.
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  • 77
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    Polymer bulletin 40 (1998), S. 741-747 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work, a series of 2,3-O-methylcellulose (MC) with different DS value were prepared. Its phase transition behavior in aqueous solution was studied in terms of DS value, concentration and molecular weight. The the following conclusions were obtained. (1) All the 2,3-O-MC samples show no sol-gel transition in aqueous solution despite the molecular weight. (2) No phase separation was observed for the 2,3-O-MCs with a DS value lower than 1.0, even when the temperature was raised to 95°C. (3) The precipitation temperature is surprisingly different between 2,3-O-MCs. and other MCs possessing comparable total DS value. (4) The precipitation temperature of 2,3-O-MCs depends on the molecular weight rather than on the concentration.
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  • 78
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Ultrahigh molecular weight polyacrylamides (PAAM) were obtained by plasma-induced polymerization in water solutions. The influenceof monomer concentration, sealing pressure, initiation time and post polymerization period on polymer yield and molecular weight were investigated. The viscosity and “screen factor” measurements, as well as the thermally stimulated depolarization currents spectroscopic data of the synthesized polymers, indicate good properties as efficient viscosity modifiers in displacement of fluids for enhance oil recovery (EOR).
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  • 79
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this report, the relaxation behavior of amorphous poly(ethylene terephthalate) (PET) in global chain orientation but nearly random segmental orientation (GOLR) state is studied by infrared dichroism, optical birefringence and hot shrinkage measurements at temperatures below or up PET's glass transition temperature, Tg. The results indicate that the difference in the relaxing rate between global chains and segments is at least in ∼ 102 times order above PET's Tg (∼ 84°C), with a rough approximation; while the sudden decrease of small Δn of the sample (∼ 10−4) upon being treated at about 85 ∼ 90°C, implies us that the small Δn is closely related with the orientation of global chains.
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  • 80
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    Polymer bulletin 41 (1998), S. 129-130 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 81
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary New biomedical polyurethanes and a polyurethane urea based on Ε-caprolactone and 1,4-butanediisocyanate have been developed. On degradation, only non-toxic products are produced. The polyurethane urea with poly(Ε-caprolactone) soft segments and butanediisocyanate/butanediamine hard segments shows a high tensile strength, a high modulus and a high resistance to tearing but as a result of the strong interactions between the solvent and the polymer processing is difficult. When butanediamine is replaced by butanediol in the chain extension step, a processible polyurethane is obtained but the polymer lacks the desired mechanical properties for biomedical applications. By chain extending with a longer urethane diol block, a processible polymer was obtained with mechanical properties comparable to the polyurethane urea. This polyurethane has been made porous and can be used as a meniscal prosthesis.
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  • 82
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Catalytic 1,3-butadiene polymerization systems can be obtained with the new complex [NbO(C16H11O6 −)(C2O4 2−)] as a catalyst. When the catalysis occurs in a homogeneous medium (toluene as a solvent) in conjunction with AlEt2Cl, cis-1,4-polybutadiene is obtained. A remarkable inversion of stereoselectivity has been observed when the catalysis is carried out in a two phase system with the molten salt AlCl3.1-methyl-3-n-butyl-imidazolium chloride (MBIC) as a solvent and AlEt2Cl as a cocatalyst, giving the trans 1,4-polybutadiene.
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  • 83
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Highly branched aliphatic molecules have been used for the first time as tethers in the preparation of polymeric chiral stationary phases. Attachment of a specifically designed chiral selector to organic porous polymer beads through a branched linker substantially increases the enantioselectivity compared to that of the equivalent separation medium with a traditional linear tether.
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  • 84
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The EPR spectra of composite dextran and carboxymethyldextran gels were studied in order to identify the functional groups involved in copper(II) complexation depending on pH. The porous structure resulting from crosslinking of polymer chains of dextran, via epichlorohydrin, forces the immobilization of Cu2+ ions surrounded by different oxygen groups of the polymer gel matrix. The different polynuclear structures are postulated to be formed depending on the type of polysaccharide derivatives. The results indicate that carboxyl and deprotonated hydroxyl groups participate in the complex formation.
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  • 85
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Individual polystyrene (PS) and polyacrylonitrile (PAN) solutions in N,N-dimethylformamide (DMF) were studied by electronic absorption spectroscopy. Upon increasing the polymer concentration in the PS-DMF binary system a bathochromic shift of the band at about 260 nm was found. This spectral effect could be explained by an association of PS phenyl groups and/or by a complex formation between DMF and PS. The UV spectrum of PAN in DMF solution was interpreted in terms of the variety of possible donor-acceptor complex formations. The specific intermolecular interactions in the investigated binary liquid systems were discussed on the basis of the spectral data.
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  • 86
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Measurement of swelling is used to estimate the extent of cross-linking of latex particles prepared by emulsion polymerization. In this paper we report swelling data as a function of solvent activity for two latexes: (1) a poly(butylacrylate) (PBA) latex, and (2) a poly(isodecylacrylate) latex. In the latter case comparison is made between the swelling behavior of fully cross-linked, i.e., networks without free polymer chains, and partially cross-linked latexes. It is demonstrated that the equilibrium swelling properties are only slightly affected by the presence of uncross-linked chains. Swelling gives reliable results for the cross-link density only if the latex does not contain free chains.
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  • 87
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary A correlation between interface strength and data of acoustic emission measurements in particle filled polymer composites was found. The method allows the evaluation of the interface strength in situ in polymer composite specimens at uniaxial loading. The measurements have shown that the tailored interface with the monomolecular tethered polymer layers of various grafting density change the mechanism of microdefect formation.
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  • 88
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By using the redox reaction between Ce(IV) and terminal -CH2OH groups of polyethylene oxide(PEO), block copolymers composed of poly(N-isopropylacrylamide)(PNiPAAm) and poly(ethylene oxide) was prepared. The aqueous solution of the block copolymers exhibited thermal phase transition and the phase transition temperature of these block copolymers became higher than the PNiPAAm homopolymer.
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  • 89
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    Polymer bulletin 40 (1998), S. 469-476 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline diols containing a biphenyl mesogenic core, methoxy or cyano terminal groups and spacers of various lengths were synthesized and used for the preparation of side-chain thermotropic polyurethanes. The structure of the synthesized diols and polymers was confirmed by elemental analysis, FTIR and NMR spectroscopy. Phase transition temperatures were studied by DSC, while optical textures were characterized by polarizing microscopy. A smectic type arrangement was found for the mesophases of all products.
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  • 90
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    Polymer bulletin 40 (1998), S. 485-490 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Brittle polylactide (PLA) was toughened by introducing 5 wt % of a poly(ɛ-caprolactone)(PCL) diol- and triol-based polyurethane (PU) network. The extent of cross-linking of the PU was varied by changing the ratio between diol and triol. The effects of the PU content and its crosslink density on the mechanical properties and the toughness of PU/PLA blends were investigated. Maximum toughness of PU/PLA blends, an order of magnitute higher than that of pure PLA, could be achieved by the use of a proper amount of PU and a proper extent of cross-linking.
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  • 91
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Effects of cyclization and ionic group contents on the termination rate of macroradicals formed at zero monomer conversion were investigated. For this purpose, the pregel regime of free-radical methyl methacrylate / ethylene glycol dimethacrylate (MMA/EGDM) and acrylamide / N,N'-methylenebisacrylamide (AAm/BAAm) copolymerization systems was studied by means of the dilatometric technique. To eliminate the chain-length dependent variation of the termination rates, different sets of experiments were carried out each at a fixed monomer and initiator concentration. At low crosslinker contents, the termination rate of zero-conversion macroradicals was enhanced in crosslinking copolymerizations compared to linear polymerization. This is due to the cyclization reactions which reduce the size of the macroradical coils and thus, enhance the termination rates due to the lowering of the thermodynamic excluded volume effect. As the amount of the crosslinker increases, an enhancement in the initial rate of polymerization is observed in all series of experiments, indicating that steric effects on segmental diffusion dominate at high crosslinker contents. The results also indicate a slower rate of termination of ionic macroradicals compared to the non-ionic radicals of the same molecular weight and points the significance of the thermodynamic excluded volume effect on rising the ionic group content.
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  • 92
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    Polymer bulletin 40 (1998), S. 525-532 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography.
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  • 93
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Functionalized oligo-ɛ-caprolactones synthesized by heterogeneous coordinated anionic ring opening polymerization (AROP) in protic conditions have been analyzed by mass spectrometry in order to investigate the molecular weight distribution as well as the possible occurrence of macrocycles. Mass spectra obtained from LSIMS revealed the presence of fragmentation products and some of them have been identified. Macrocycles were also detected. Nevertheless, ESI and MALDI-TOF spectrometries do not confirm the presence of macrocycles in the samples. The same results have been obtained by analysis of commercially available polycaprolactones.
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  • 94
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thin films of phase separated polystyrene-b-polyisoprene-b-polystyrene block copolymers were studied by tapping mode atomic force microscopy. The relative contrast in height and phase mode images of the phase separated regions was found to be very sensitive to changes in the operating conditions of the microscope. Contrast variations and reversals were observed for height and phase mode images as a function of the set-point amplitude ratio and drive frequency. No unique height or phase contrast was observed for the the tri-block copolymer system examined in this study.
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  • 95
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dielectric constants of allyl methacrylate-methyl methacrylate copolymers are measured in toluene solution at a constant frequency of 2 MHz, within a wide temperature range (20–70°C). Soluble copolymers have been prepared by group transfer copolymerization. Dipole moments are calculated from Guggenheim-Smith equation. The effects of allyl group on the dipole moments of copolymers in a slightly polar medium are discussed.
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  • 96
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Influence of some aromatic amino acids (histidine, phenylalanine and tryptophan) on the swelling behavior of acrylamide/maleic acid hydrogel (AAm/MA) prepared by γ-radiation was investigated. Swelling tests of AAm/MA hydrogel were made in buffer solutions and amino acid solutions at various pH at 37°C. The pH values are ionization of α-carboxyl groups (pK'1), α-amino groups (pK'2) and, isoelectric points (pI) of amino acids. The swelling of AAm/MA hydrogel increased when pH values of solutions were increased. The value of equilibrium swelling of AAm/MA hydrogel was 1035% at pH 10 buffer, while it was 880% at pH 2 buffer. The values of equilibrium swelling of AAm/MA hydrogel in phenylalanine, tryptophan and histidine solutions varied among 1130–1245% at pH 10, while they were among 790–975% at pH 2. The rate constant of swelling, diffusional exponent, network parameter and, diffusion and intrinsic diffusion coefficient were calculated by swelling kinetics. Diffusion of the penetrants into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 3.33×10−6– 7.71×10−6 cm 2s−1, while the intrinsic diffusion coefficients waried between 4.03×10−6– 8.48×10−6 cm 2s−1.
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  • 97
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    Polymer bulletin 40 (1998), S. 599-605 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to characterize the low temperature relaxation of epoxy resin modified with amine-terminated butadiene acrylonitrile copolymers (ATBN), thermally stimulated current (TSC) and relaxation map analysis (RMA) were investigated. Four relaxation peaks at around −140, −100, −60 and 0°C were observed as the indication of γ-, β-relaxation of epoxy resin, Tg, new unknown peak of ATBN, respectively. The unknown peak at around 0°C was observed due to dipole orientation. The RMA data was showed that compensation temperature (Tc) and degree-of-disorder (DOD) were increased with increasing the content of acrylonitrile and ATBN, whereas the compensation time (τc) was decreased. It can be concluded that the cooperative molecular motion in cured epoxy resin was more active as the concentration of acrylonitrile and ATBN content increases.
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  • 98
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    Polymer bulletin 40 (1998), S. 639-645 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Bifunctional living polytetrahydrofuran (PTHF) was terminated with potassium salt of pyrrole to yield polymers with electrochemically active end groups. These polymers were employed in the second stage to obtain conducting polypyrrole/polytetrahydrofuran block copolymers with short and long polytetrahydrofuran segments by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Syntheses of block copolymers were achieved in media where tetrabutylammonium fluoroborate, sodium perchlorate and sodium p-toluenesulfonate were used as the supporting electrolytes. Characterizations were based on DSC, TGA, SEM, FTIR, and CV analyses. No significant effect of the chain length of polytetrahydrofuran segments on the properties of the copolymers was observed; however, thermal, electrochemical behaviors, and surface morphologies of the films were greatly affected by the supporting electrolytes.
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  • 99
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effects of molecular structure of graft copolymer on the interfacial properties are investigated using a Monte Carlo simulation. The interfacial activity is analyzed by calculating the surface coverage and the concentration profile of graft copolymer at the interface. At low interaction energy between two segments, the graft copolymer having fewer grafting sites and longer grafting chains locates better at the interface than the graft copolymer having more grafting sites and shorter grafting chain. At high interaction energy, this situation is reversed: the graft copolymer with more grafting sites locates better than the copolymer with fewer grafting sites.
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  • 100
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers containing vinyltrimethylsilane and vinyltrimethoxysilane with N-vinyl-2-pyrrolidone at different compositions were synthesized and characterized. The reactivity ratios was estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. These parameters were also estimated through a computer program based on nonlinear minimization algorithm, starting from the r1 and r2 values obtained by the former procedures. The analysis of the results allow us to interpret the reactivity behaviour of these polymers in terms of the relative reactivity of the substiuents. The effect of the chemical structure of the polymer side group is discussed in terms of the different contributions to the stabilization of the radical intermediates.
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