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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 149 (1988), S. 261-267 
    ISSN: 1432-072X
    Keywords: Yeast ; Hanseniaspora uvarum ; Pichia kluyveri ; Killer toxin ; dsRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract By heat treatment killer strains of the type K1 of Saccharomyces cerevisiae that are known to harbour dsRNA plasmids were completely cured, whereas only a small fraction of the clones of the killer type K2 had lost the dsRNA dependent killer character. The K2 killers but not the strains of killer type K1 were easily cured by cycloheximide. Killer strains of Hanseniaspora uvarum were not curable by heat treatment. Curing was successfull with cycloheximide or 5-fluorouracil. Two double-stranded RNA plasmids were detected in the killer strains of H. uvarum. The smaller dsRNA plasmid was absent in the strains that were cured of their killer character by 5-fluorouracil. The killer character of H. uvarum was transferred to S. cerevisiae by spheroplast fusion. The fusion products showing the killer character contained both dsRNA plasmids, obviously the smaller plasmid (M-dsRNA) carries the genes for killer toxin formation. Killer strains of Pichia kluyveri were not curable of their killer character, in these strains no dsRNA plasmids were detected.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 416-422 
    ISSN: 1573-0972
    Keywords: Amylase ; Candida utilis ; grain sorghum ; Lipomyces kononenkoae ; protein ; Schwanniomyces occidentalis ; starch ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cultivation of aSchwanniomyces occidentalis derepressed mutant in a 10% (w/v) gelatinized grain sorghum slurry increased the crude protein content of the biomass from an initial value of 12% to 41% (dry) within 20 h, with no detectable residual starch. Co-cultivation ofCandida utilis with theS. occidentalis mutant improved the final crude protein content to 47% within 18 h, whereas a co-culture ofC. utilis with aLipomyces kononenkoae mutant resulted in a cultivation time of 50 h with a significantly lower protein content and a low final α-amylase activity. In a 15% (w/v) grain sorghum slurry aC. utilis/S. occidentalis co-culture increased the protein content to about 44% within 30 h. Yeast cultivation increased the lysine and threonine content of the final biomass considerably.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 514-520 
    ISSN: 1573-0972
    Keywords: Astaxanthin ; mannitol ; mutants ; NTG ; Phaffia rhodozyma ; succinate ; valine ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Mutagenesis of Phaffia rhodozyma with NTG yielded a mutant with an astaxanthin content of 1688 μg (g dry biomass)-1, a cell yield coefficient of 0.47 on glucose and a maximum specific growth rate of 0.12 h-1. Re-mutation of the mutant decreased the cell yield and maximum specific growth rate but increased the astaxanthin content. The use of mannitol or succinate as carbon sources enhanced pigmentation, yielding astaxanthin contents of 1973 μg g-1 and 1926 μg g-1, respectively. The use of valine as sole nitrogen source also increased astaxanthin production, but severely decreased the maximum specific growth rate and cell yield coefficient. The optimum pH for growth of P. rhodozyma was between pH 4.5 and 5.5, whereas the astaxanthin content remained constant above pH 3.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 357-360 
    ISSN: 1573-0972
    Keywords: Candida utilis ; inhibition ; kinetics ; regulation ; sugar ; transport ; xylose ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Low-affinity (K m=67.6±3.2 mM) and high-affinity (K m=1.9±1.2 mM) D-xylose transport occur in Candida utilis grown, respectively, on D-glucose or D-xylose. Starvation of glucose-grown cells decreases the K m value (10.5±2.6 mm). The high-affinity system appearing during starvation required protein synthesis and it was inactivated when cells were exposed to glucose, by a process independent of protein synthesis. High-affinity transport was accompanied by transient alkalinization of yeast suspensions, indicating that it is a proton symport, whereas low-affinity transport was not. Both systems, however, were inhibited by metabolic inhibitors and by replacing H2O in the transport assay with D2O, indicating that both may be proton symports. Glucose and acetic acid also inhibited both high-and low-affinity xylose transport.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 434-438 
    ISSN: 1573-0972
    Keywords: Acetic acid ; l-aribinose ; Candida blankii ; chemostat ; hemicellulose hydrolysate ; d-xylose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The growth characteristics ofCandida blankii as a function of temperature and pH in a simulated bagasse hemicellulose hydrolysate were determined in chemostat culture. The highest maximum specific growth rate of 0.44h−1 was reached at 38°C and at pH 5.5, with a sharp decrease in growth rate on either side of this temperature. Growth occurred at 46°C but not at 48°C. The protein and cell yields varied little below 40°C and the respective values were 0.22 and 0.5 g/g at 38°C. At the lower pH values, a severe linear decrease in cell and protein yields occurred, whereas a small increase in these yields at decreasing pH values was found when acetic acid was omitted from the medium. In the presence of acetic acid, a very sharp decrease in the growth rate at pH values below pH 4.5 was noted, despite the very low residual acetic acid concentrations, of less than 50 mg/l, in the culture.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 93-99 
    ISSN: 1573-0972
    Keywords: Fusarium moniliforme ; gibberellic acid ; maize flour ; solid state ; starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The production of gibberellic acid (GA3) by Fusarium moniliforme M-7121 in solid-state culture was evaluated in flask cultures as well as in 3-I horizontal rotary reactors. The highest production rate of GA3 was with 80% (w/v) maize flour mixed with wheat bran. The optimum initial moisture content was inversely dependent on the ambient relative humidity. The initial water activity range for optimal growth and GA3 accumulation was about 0.98 to 0.99, which is unusually high for a filamentous fungus. A low O2 concentration resulted in a much decreased GA3 yield and the appearance of a yellow to reddish pigmentation in the mycelium. The lag phase was short and rapid growth continued for up to 2 days in the rotary reactor, with a maximum specific growth rate of 0.12 h−1. The maximum rate of GA3 production occurred during the subsequent 3 to 10 days of incubation and the final GA3 concentration reached was 18.7 mg to 19.3 mg/g dry culture. The point of maximum GA3 accumulation after 10 to 12 days of incubation was usually marked by a sharp increase in pH.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 505-509 
    ISSN: 1573-0972
    Keywords: Acetic acid ; chemostat ; Geotrichum ingens ; growth ; inhibition ; kinetics ; monocarboxylic acids ; propionic acid ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Growth of Geotrichum ingens in batch cultures was completely inhibited by 47 g acetic acid/l or 33 g propionic acid/I. With mixtures of acetic and propionic acids, however, growth only ceased at 55 g/l. Acetic acid inhibited growth linearly, whereas propionic acid inhibited growth non-linearly. In continuous culture, two steady states at each dilution rate were observed at high dilution rates for acetic acid and propionic acid. The highest yield coefficient (0.69 g cells/g substrate) was achieved with propionic acid as substrate. On both substrates and their mixtures, the protein content of the biomass increased when the dilution rate was increased.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-0972
    Keywords: Fed-batch ; fatty acids ; gamma-linolenic acid ; monocarboxylic acids ; Mucor ; polyunsaturated fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Fischer-Tropsch reaction water, which contains C2 to C5 monocarboxylic acids, generated as a co-product of the Sasol industrial oil-from-coal process, constitutes a potential cheap carbon substrate for the production of gamma-linolenic acid (GLA) by selced Mucor species. Three strains of Mucor were each grown in an air-lift reactor operated in a fed-batch, pH-stat mode under N-limitation with a mixture of C2 to C5 monocarboxylic acids as both pH titrant and carbon source. The production of GLA from this substrate was evaluated. Growth typically resulted in the rapid assimilation of acetic, n-butyric and n-valeric acids. Although propionic, iso-butyric and iso-valeric acids were assimilated to varying degrees, these acids accumulated in the culture. Mucor circinelloides CBS 203.28 gave the best results in that it assimilated 36% to 100% of each acid, had a biomass yield coefficient of 0.3 (calculated on acids utilized), and contained 28% crude oil, 84% of which comprised neutral lipids with a GLA content of 14.4%, giving 33 mg GLA/g biomass. GLA accumulation coincided with a decrease in the stearic-acid content of the neutral-lipid fraction. The results were comparable with previous results obtained with acetic acid and glucose as sole carbon sources, demonstrating the feasibility of producing GLA from the above mixture of organic acids.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 24 (2000), S. 231-236 
    ISSN: 1476-5535
    Keywords: Keywords: Saccharomyces cerevisiae; aerobic; chemostat; growth kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerobic glucose-limited chemostat cultivations were conducted with Saccharomyces cerevisiae strains NRRL Y132, ATCC 4126 and CBS 8066, using a complex medium. At low dilution rates all three strains utilised glucose oxidatively with high biomass yield coefficients, no ethanol production and very low steady-state residual glucose concentrations in the culture. Above a threshold dilution rate, respiro-fermentative (oxido-reductive) metabolism commenced, with simultaneous respiration and fermentation occurring, which is typical of Crabtree-positive yeasts. However, at high dilution rates the three strains responded differently. At high dilution rates S. cerevisiae CBS 8066 produced 7–8 g ethanol L−1 from 20 g glucose L−1 with concomitant low levels of residual glucose, which increased markedly only close to the wash-out dilution rate. By contrast, in the respiro-fermentative region both S. cerevisiae ATCC 4126 and NRRL Y132 produced much lower levels of ethanol (3–4 g L−1) than S. cerevisiae CBS 8066, concomitant with very high residual sugar concentrations, which was a significant deviation from Monod kinetics and appeared to be associated either with high growth rates or with a fermentative (or respiro-fermentative) metabolism. Supplementation of the cultures with inorganic or organic nutrients failed to improve ethanol production or glucose assimilation. Journal of Industrial Microbiology & Biotechnology (2000) 24, 231–236.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 21 (1996), S. 77-83 
    ISSN: 1432-0789
    Keywords: Denitrification ; Field experiment ; Acetylene inhibition technique ; Nitrate ; Soil moisture ; Vicia faba ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Denitrification rates were studied using the C2H2 inhibition technique in a 2-year field experiment within plots of nodulated and non-nodulated faba beans, ryegrass, and cabbage. Denitrification rates ranged from 14.40 to 0.02 ng N2O−N g−1 soil dry weight h−1. Mean denitrification increased fourfold in plots of N2−fixing Vicia faba compared to non-nodulated V. faba mutant F48, Lolium perenne, and Brassica oleracea. The results with and without C2H2 treatment indicate that in the field the major part of this enhanced denitrification led to the endproduct N2 rather than to the ozone-degrading N2O. Higher denitrification rates of plots with N2−fixing plants in September seemed to be caused by an increase in soil NO inf3 sup- of about 20 kg ha−1 found between July and August. Soil NO inf3 sup- and soil moisture explained 67% of the variation in denitrification rates of the different soil samples over the growing seasons in the 2 years. Soil moisture explained 44% of the variation for soil planted with N2−fixing plants and 62% for soil planted with non-fixing plants. Positive exponential relationships were obtained between denitrification rates and soil nitrate (r=0.71) and soil moisture (r=0.82).
    Type of Medium: Electronic Resource
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