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  • 1
    Electronic Resource
    Electronic Resource
    Uncoupled glycerol distribution as the origin of the accumulation of 3-hydroxypropionaldehyde during the fermentation of glycerol by Enterobacter agglomerans CNCM 1210 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 303-305 
    Details
    ISSN: 0006-3592
    Keywords: glycerol ; Enterobacter agglomerans ; 3-hydroxypropionaldehyde ; catabolic limitation ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch fermentation of glycerol to 1,3-propanediol (1,3PPD) by Enterobacter agglomerans CNCM 1210 showed the lethal accumulation of 3-hydroxypropionaldehyde (3-HPA) when performed under initial substrate content higher than 40 g/L. Assigned to the inhibition by the NAD/NADH ratio of the 3-HPA converting enzyme: 1,3PPD dehydrogenase, intracellular assays were conducted in an attempt to identify the metabolic mechanisms involved in the increase of that ratio. An overflow metabolism through the 1,3PPD formation pathway was established, while a catabolic limitation in the oxidative branch at the level of glyceraldehyde-3-phosphate dehydrogenase occurred. Uncoupled activities of synthesis and consumption of reducing equivalents are thus suspected to provoke the increase of the NAD/NADH ratio and the subsequent accumulation of 3-HPA. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:303-305, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Malolactic fermentation by engineered Saccharomyces cerevisiae as compared with engineered Schizosaccharomyces pombe (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 215-225 
    Details
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; Schizosaccharomyces pombe ; Lactococcus lactis ; malolactic enzyme ; malolactic fermentation ; heterologous expression ; NMR ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The ability of yeast strains to perform both alcoholic and malolactic fermentation in winemaking was studied with a view to achieving a better control of malolactic fermentation in enology. The malolactic gene of Lactococcus lactis (mleS) was expressed in Saccharomyces cerevisiae and Schizosaccharomyces pombe. The heterologous protein is expressed at a high level in cell extracts of a S. cerevisiae strain expressing the gene mleS under the control of the alcohol dehydrogenase (ADH1) promoter on a multicopy plasmid. Malolactic enzyme specific activity is three times higher than in L. lactis extracts. Saccharomyces cerevisiae expressing the malolactic enzyme produces significant amounts of l-lactate during fermentation on glucose-rich medium in the presence of malic acid. Isotopic filiation was used to demonstrate that 75% of the l-lactate produced originates from endogenous l-malate and 25% from exogenous l-malate. Moreover, although a small amount of exogenous l-malate was degraded by S. cerevisiae transformed or not by mleS, all the exogenous degraded l-malate was converted into l-lactate via a malolactic reaction in the recombinant strain, providing evidence for very efficient competition of malolactic enzyme with the endogenous malic acid pathways. These results indicate that the sole limiting step for S. cerevisiae in achieving malolactic fermentation is in malate transport. This was confirmed using a different model, S. pombe, which efficiently degrades l-malate. Total malolactic fermentation was obtained in this strain, with most of the l-malate converted into l-lactate and CO2. Moreover, l-malate was used preferentially by the malolactic enzyme in this strain also.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Evidence for a selective and electroneutral K+/H+-exchange in Saccharomyces cerevisiae using plasma membrane vesicles (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 1301-1313 
    Details
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; plasma membrane purification ; vesicles reconstitution ; K+/H+-exchange ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The existence of a K+/H+ transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly-sealed inside-out plasma membrane vesicles. In these vesicles, the K+/H+ transport system, which is able to catalyse both K+ influx and efflux, is mainly driven by the K+ transmembrane gradient and can function even if the plasma membrane H+-ATPase is not active. Using the anionic oxonol VI and the cationic DISC2(5) probes, it was shown that a membrane potential is not created during K+ fluxes. Such a dye response argues for the presence of a K+/H+ exchange system in S. cerevisiae plasma membrane and established the non-electrogenic character of the transport. The maximal rate of exchange is obtained at pH 6·8. This reversible transport system presents a high selectivity for K+ among other monovalent cations and a higher affinity for the K+ influx into the vesicles (exit from cells). The possible role of this K+/H+ exchange system in regulation of internal potassium concentration in S. cerevisiae is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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