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  • 1
    Electronic Resource
    Electronic Resource
    Anaerobic growth and improved fermentation of Pichia stipitis bearing a URA1 gene from Saccharomyces cerevisiae (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 339-345 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Respiratory and fermentative pathways co-exist to support growth and product formation in Pichia stipitis. This yeast grows rapidly without ethanol production under fully aerobic conditions, and it ferments glucose or xylose under oxygen-limited conditions, but it stops growing within one generation under anaerobic conditions. Expression of Saccharomyces cerevisiaeURA1 (ScURA1) in P. stipitis enabled rapid anaerobic growth in minimal defined medium containing glucose when essential lipids were present. ScURA1 encodes a dihydroorotate dehydrogenase that uses fumarate as an alternative electron acceptor to confer anaerobic growth. Initial P. stipitis transformants grew and produced 32 g/l ethanol from 78 g/l glucose. Cells produced even more ethanol faster following two anaerobic serial subcultures. Control strains without ScURA1 were incapable of growing anaerobically and showed only limited fermentation. P. stipitis cells bearing ScURA1 were viable in anaerobic xylose medium for long periods, and supplemental glucose allowed cell growth, but xylose alone could not support anaerobic growth even after serial anaerobic subculture on glucose. These data imply that P. stipitis can grow anaerobically using metabolic energy generated through fermentation but that it exhibits fundamental differences in cofactor selection and electron transport with glucose and xylose metabolism. This is the first report of genetic engineering to enable anaerobic growth of a eukaryote.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051301
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  • 2
    Electronic Resource
    Electronic Resource
    The detection of elements in larval otoliths from Atlantic herring using laser ablation ICP-MS (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 63 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Trace element concentrations of otoliths from larval herring Clupea harengus collected from known spawning beds in the Celtic and Irish Seas, were investigated using laser ablation ICP-MS and compared with concentrations in the larval cores of juvenile otoliths from the same populations and year class. A range of elements (Mg, Zn, Sr, Ba and Pb) was detectable in early larval otoliths (20–40 µm diameter). Larval otolith concentrations exceeded the larval core concentrations of juvenile otoliths and also the concentrations reported in the literature, for Mg, Zn, Ba and Pb, indicating that the measurement of elements in larval otoliths was severely affected by post-mortem contamination, most likely due to adherence of tissue and endolymph residue on the otolith surface. Comparison of otolith composition between larvae from two freezing treatments showed that contamination from Mg and Zn was more serious in otoliths that had remained in frozen larvae for prolonged periods. Larval populations from the two seas showed significant differences in otolith Sr concentrations, which were consistent over two sampling years. Similar differences were seen in the corresponding juvenile populations. The results show that while early larval otoliths are extremely susceptible post-mortem contamination, Sr concentrations can be reliably measured using laser ablation ICP-MS and for this element, the detection of region specific differences is possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00223.x
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  • 3
    Electronic Resource
    Electronic Resource
    An improvement in Pichia stipitis fermentation of acid-hydrolysed hemicellulose achieved by overliming (calcium hydroxide treatment) and strain adaptation (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 281-283 
    Details
    ISSN: 1573-0972
    Keywords: Adaptation ; fermentation ; hemicellulose ; hydrolysate ; overliming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The fermentability of a corn cob, acid-hydrolysed hemicellulose by Pichia stipitis was considerably improved by pre-treatment with Ca(OH)2. The total sugars utilized and ethanol yield for the untreated hydrolysate were 18% and 0.21 g/g, respectively, compared with 82% and 0.32 g/g respectively for the treated material. Adaptation of the yeast to the hydrolysate resulted in a significantly higher fermentation rate with over 90% of the initial total sugars being utilized and an ethanol yield and maximum ethanol concentration of 0.41 g/g and 13.3 g/l, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00360928
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of environmental conditions on production of xylitol byCandida boidinii (1995)
    Springer
    World journal of microbiology and biotechnology 11 (1995), S. 213-218 
    Details
    ISSN: 1573-0972
    Keywords: Candida boidinii ; xylitol production ; xylose fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Candida boidinii NRRL Y-17213 produced more xylitol thanC. magnolia (NRRL Y-4226 and NRRL Y-7621),Debaryomyces hansenii (C-98 M-21, C-56 M-9 and NRRL Y-7425), orPichia (Hansenula) anomala (NRRL Y-366). WithC. boidinii, highest xylitol productivity was at pH 7 but highest yield was at pH 8, using 5 g urea and 5 g Casamino acids/I. Decreasing the aeration rate decreased xylose consumption and cell growth but increased the xylitol yield. When an initial cell density of 5.1 g/l was used instead of 1.3 g/l, xylitol yield and the specific xylitol production rate doubled. Substrate concentration had the greatest effect on xylitol production; increasing xylose concentration 7.5-fold (to 150 g/l) gave a 71-fold increase in xylitol production (53 g/l) and a 10-fold increase in xylitol/ethanol ratio. The highest xylitol yield (0.47 g/g), corresponding to 52% of the theoretical yield, was obtained with 150 g xylose/l after 14 days. Xylose at 200 g/l inhibited xylitol production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704652
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  • 5
    Electronic Resource
    Electronic Resource
    Alkaline-active xylanase produced by an alkaliphilicBacillus sp isolated from kraft pulp (1995)
    Springer
    Journal of industrial microbiology and biotechnology 15 (1995), S. 434-441 
    Details
    ISSN: 1476-5535
    Keywords: enzymatic prebleaching ; alkaliphilicBacillus ; xylanase ; chromophore release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract ABacillus sp (V1-4) was isolated from hardwood kraft pulp. It was capable of growing in diluted kraft black liquor at pH 11.5 and produced 49 IU (μmol xylose min−1 ml−1) of xylanase when cultivated in alkaline medium at pH 9. Maximal enzyme activity was obtained by cultivation in a defined alkaline medium with 2% birchwood xylan and 1% corn steep liquor at pH 9, but high enzyme production was also obtained on wheat bran. The apparent pH optimum of the enzyme varied with the pH used for cultivation and the buffer system employed for enzyme assay. With cultivation at pH 10 and assays performed in glycine buffer, maximal activity was observed at pH 8.5; with phosphate buffer, maximal activity was between pH 6 and 7. The xylanase temperature optimum (at pH 7.0) was 55°C. In the absence of substrate, at pH 9.0, the enzyme was stable at 50°C for at least 30 min. Elecrophoretic analysis of the crude preparation showed one predominant xylanase with an alkaline pl. Biobleaching studies showed that the enzyme would brighten both hardwood and softwood kraft pulp and release chromophores at pH 7 and 9. Because kraft pulps are alkaline, this enzyme could be used for prebleaching with minimal pH adjustment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569971
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  • 6
    Electronic Resource
    Electronic Resource
    Cloning and disruption of the b-isopropylmalate dehydrogenase gene (LEU2 ) of Pichia stipitis with URA3 and recovery of the double auxotroph (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 141-146 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Transformation of Pichia stipitis is required to advance genetic studies and development of xylose metabolism in this yeast. To this end, we used P. stipitis URA3 (PsURA3) to disrupt P. stipitis LEU2 in a P. stipitis ura3 mutant. A highly fermentative P. stipitis mutant (FPL-DX26) was selected for resistance to 5′-fluoroorotic acid to obtain P. stipitis FPL-UC7 (ura3-3). A URA3:lacZ“pop-out” cassette was constructed containing PsURA3 flanked by direct repeats from segments of the lacZ reading frame. The P. stipitis LEU2 gene (PsLEU2) was cloned from a P. stipitis CBS 6054 genomic library through homology to Saccharomyces cerevisiae LEU2, and a disruption cassette was constructed by replacing the PsLEU2 reading sequence with the PsURA3:lacZ cassette. FPL-UC7 (ura3-3) was transformed with the disruption cassette, and a site-specific integrant was identified by selecting for the Leu− Ura+ phenotype. The ura3 marker was recovered from this strain by plating cells onto 5′-fluoroorotate and screening for spontaneous URA3 deletion mutants. Excision of the flanked PsURA3 gene resulted in the Leu−Ura− phenotype. The double auxotrophs are stable and can be transformed at a high frequency by PsLEU2 or PsURA3 carried on autonomous-replication-sequence-based plasmids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051150
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  • 7
    Electronic Resource
    Electronic Resource
    Chromophore release from kraft pulp by purified streptomyces roseiscleroticus xylanases (1993)
    Springer
    Applied microbiology and biotechnology 39 (1993), S. 405-412 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Treating kraft pulps with the crude xylanase from Streptomyces roseiscleroticus followed by alkali extraction reduces the kappa number in a linear manner with enzyme doses up to about 3 IU/gm of oven-dry pulp. The enzyme complex consists of four isoenzymes designated Xyl1, Xyl2, Xyl3 and Xyl4. Each can release chromophores when used alone and each can facilitate alkali extraction to reduce the kappa number, but their relative abilities are different. Of the four isozymes, Xyl4 releases the least color and 237-nm-absorbing material whereas Xyl3 releases the most. Xyl4 best enhances the ability of alkali to reduce the kappa number. The UV absorption spectrum of the material released by alkali extraction differs significantly from the spectral characteristics of that released during enzyme treatment. The alkali-solubilized material has a maximum absorptivity at 265 nm and relatively little absorptivity at 237 nm. The material released during enzyme treatment absorbs strongly at 205 and 237 nm. UV/VIS spectroscopy of the enzyme- or alkali-released material does not show a characteristics lignin peak at 280 nm, nor does it reveal any notable peaks in the visible region. Analysis of the material released by enzyme treatment revealed more than 40 product peaks after fractionation by reversed-phase HPLC. We observed many products with strong UV absorption. These were relatively hydrophilic. Fewer products absorbed in the visible region. These were more hydrophobic. All four isoenzymes exhibit endo-action patterns; none forms xylose from oat-spelt xylan. The action patterns fell into two groups: endo-1 enzymes (Xyl1 and Xyl3) formed xylotriose (X3) and other lower oligosaccharides as the predominant products; endo-2 enzymes (Xyl2 and Xyl4) formed roughly equimolar amounts of X3, xylotetraose (X4), and xylopentaose (X5), and tended to leave larger amounts of undigested higher oligosaccharides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192102
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  • 8
    Electronic Resource
    Electronic Resource
    Levels of pentose phosphate pathway enzymes fromCandida shehatae grown in continuous culture (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 282-288 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Candida shehatae exhibits different fermentative capacities when grown under different aeration conditions. These studies investigated the titers of xylose reductase, xylitol dehydrogenase, glucose-6-phosphate dehydrogenase and alcohol dehydrogenase in crude extracts ofCandida shehatae grown in continuous culture with various specific aeration rates. Carbon source, aeration rate, dilution rate and temperature were examined as variables. Xylose reductase and xylitol dehydrogenase were induced by xylose and were largely absent in glucose-grown cells. Alcohol dehydrogenae levels were higher in glucose-grown cells than in xylose-grown cells. The levels of this enzyme also correlated with the fermentative character of metabolism, having a low value under fully aerobic conditions, a high value under anaerobic conditions, and intermediate levels under various semi-aerobic conditions. Temperature had no effect on any enzyme level over the range of 20–30°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01982917
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  • 9
    Electronic Resource
    Electronic Resource
    Xylose metabolism by Candida shehatae in continuous culture (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 478-486 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Xylose metabolism by Candida shehatae in continuous culture was examined under both fully-aerobic and semi-aerobic conditions. Growth did not occur in the absence of respiration. Under fully-aerobic conditions, the cell yield was constant at 0.51 g/g and the specific respiration rate Q o 2 was linearly related to the specific growth rate μ with a slope of 15 mmol g-1 and an intercept of 1.2 mmol g-1 h-1. Under semi-aerobic conditions, Q O 2 was proportional to μ with a slope consistent with a cell yield from oxygen Y O 2 of 35±7 g mol-1. The specific xylose uptake rate was a constant independent of μ and equal to the maximum rate of xylose transport. Ethanol production was observed under semi-aerobic conditions only, and the specific fermentation rate was inversely related to μ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268219
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  • 10
    Electronic Resource
    Electronic Resource
    Levels of pentose phosphate pathway enzymes fromCandida shehatae grown in continuous culture (1988)
    Springer
    Applied microbiology and biotechnology 29 (1988), S. 282-288 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Candida shehatae exhibits different fermentative capacities when grown under different aeration conditions. These studies investigated the titers of xylose reductase, xylitol dehydrogenase, glucose-6-phosphate dehydrogenase and alcohol dehydrogenase in crude extracts ofCandida shehatae grown in continuous culture with various specific aeration rates. Carbon source, aeration rate, dilution rate and temperature were examined as variables. Xylose reductase and xylitol dehydrogenase were induced by xylose and were largely absent in glucose-grown cells. Alcohol dehydrogenae levels were higher in glucose-grown cells than in xylose-grown cells. The levels of this enzyme also correlated with the fermentative character of metabolism, having a low value under fully aerobic conditions, a high value under anaerobic conditions, and intermediate levels under various semi-aerobic conditions. Temperature had no effect on any enzyme level over the range of 20–30°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00939322
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