Transport of ethanol in baker’s yeast

Alonso, Alberto Gómez

doi:10.1007/bf02922503

Cited by 20 publications

(13 citation statements)

References 4 publications

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“…The equilibrium distribution coefficient of solutes into this water appears to be higher than that of the cytoplasmic water [75,76], mainly due to the contribution of the periplasmic space, and so whole cell coefficients are typically higher than the true cytoplasmic value. The equilibrium distribution of xylose into these same cells was only 0.87 [36], a result which has been confirmed by other workers [77]. The equilibrium distribution of xylose into these same cells was only 0.87 [36], a result which has been confirmed by other workers [77].…”

Section: Distribution Into Cell Watersupporting

confidence: 70%

“…Several workers have attempted to test this hypothesis and have shown that the presence of ethanol analogues, drastic pH changes, alteration of membrane-thiol and amino-groups by chemical agents and the presence of inhibitors of energy metabolism have no effect on the rate of ethanol influx or efflux or upon the equilibrium distribution coefficient [35,36,38,44]. The process must therefore be entirely passive.…”

Section: Passive or Active Transportmentioning

confidence: 99%

“…In the case of whole cell distribution coefficients the water space occupied by the cell wall plus the periplasrnic space accounts for some 15 to 25% of the total cellular water [34,42,[74][75][76]. For whole yeast cells values of the distribution coefficient of around 0.95 are common [36,38]. For whole yeast cells values of the distribution coefficient of around 0.95 are common [36,38].…”

Section: Distribution Into Cell Watermentioning

confidence: 99%

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Intracellular ethanol — accumulation and exit from yeast and other cells

Jones¹

1988

FEMS Microbiology Letters

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Section: Distribution Into Cell Watersupporting

confidence: 70%

Section: Passive or Active Transportmentioning

confidence: 99%

Section: Distribution Into Cell Watermentioning

confidence: 99%

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Intracellular ethanol — accumulation and exit from yeast and other cells

Jones¹

1988

FEMS Microbiology Letters

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“…The theoretical ATP requirement for biomass formation from acetate is similar to that for ethanol (which is taken up by passive diffusion, Kotyk & Alonso 1985), i.e. 10556 mmoles ATP.100 g biomass (Table 2).…”

Section: Transport Of Weak Acidsmentioning

confidence: 75%

Physiology of yeasts in relation to biomass yields

Verduyn¹

1992

Quantitative Aspects of Growth and Metabolism of Microorganisms

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The stoichiometric limit to the biomass yield (maximal assimilation of the carbon source) is determined by the amount of CO 2 lost in anabolism and the amount of carbon source required for generation of NADPH. This stoichiometric limit may be reached when yeasts utilize formate as an additional energy source. Factors affecting the biomass yield on single substrates are discussed under the following headings: -Energy requirement for biomass formation (YATP)' YATP depends strongly on the nature of the carbon source. Cell composition. The macroscopic composition of the biomass, and in particular the protein content, has a considerable effect on the ATP requirement for biomass formation. Hence, determination of for instance the protein content of biomass is relevant in studies on bioenergetics. Transport of the carbon source. Active (i.e. energy-requiring) transport, which occurs for a number of sugars and polyols, may contribute significantly to the calculated theoretical ATP requirement for biomass formation. Pia-ratio. The efficiency of mitochondrial energy generation has a strong effect on the cell yield. The Pia-ratio is determined to a major extent by the number of proton-translocating sites in the mitochondrial respiratory chain. Maintenance and environmental factors. Factors such as osmotic stress, heavy metals, oxygen and carbon dioxide pressures, temperature and pH affect the yield of yeasts. Various mechanisms may be involved, often affecting the maintenance energy requirement. Metabolites such as ethanol and weak acids. Ethanol increases the permeability ofthe plasma membrane, whereas weak acids can act as proton conductors. Energy content of the growth substrate. It has often been attempted in the literature to predict the biomass yield by correlating the energy content of the carbon source (represented by the degree of reduction) to the biomass yield or the percentage assimilation of the carbon source. An analysis of biomass yields of Candida uti/is on a large number of carbon sources indicates that the biomass yield is mainly determined by the biochemical pathways leading to biomass formation, rather than by the energy content of the substrate.

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“…According to Kotyk and Alonso (1985), who reported a high diffusivity of ethanol in biological membranes, the supply of ethanol as co-substrate for regeneration of NADH by ADH should hardly be limiting for r s .…”

Section: Whole-cell Catalysts For O-chloroacetophenone Reductionmentioning

confidence: 99%

Enzyme identification and development of a whole‐cell biotransformation for asymmetric reduction ofo‐chloroacetophenone

Kratzer

Pukl

Egger

et al. 2010

Biotech & Bioengineering

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Chiral 1-(o-chlorophenyl)-ethanols are key intermediates in the synthesis of chemotherapeutic substances. Enantioselective reduction of o-chloroacetophenone is a preferred method of production but well investigated chemo- and biocatalysts for this transformation are currently lacking. Based on the discovery that Candida tenuis xylose reductase converts o-chloroacetophenone with useful specificity (kcat/Km=340 M(-1) s(-1)) and perfect S-stereoselectivity, we developed whole-cell catalysts from Escherichia coli and Saccharomyces cerevisiae co-expressing recombinant reductase and a suitable system for recycling of NADH. E. coli surpassed S. cerevisiae sixfold concerning catalytic productivity (3 mmol/g dry cells/h) and total turnover number (1.5 mmol substrate/g dry cells). o-Chloroacetophenone was unexpectedly "toxic," and catalyst half-life times of only 20 min (E. coli) and 30 min (S. cerevisiae) in the presence of 100 mM substrate restricted the time of batch processing to maximally ∼5 h. Systematic reaction optimization was used to enhance the product yield (≤60%) of E. coli catalyzed conversion of 100 mM o-chloroacetophenone which was clearly limited by catalyst instability. Supplementation of external NAD+ (0.5 mM) to cells permeabilized with polymyxin B sulfate (0.14 mM) resulted in complete conversion providing 98 mM S-1-(o-chlorophenyl)-ethanol. The strategies considered for optimization of reduction rate should be generally useful, however, especially under process conditions that promote fast loss of catalyst activity.

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Transport of ethanol in baker’s yeast

Abstract: Ethanol is transported into various strains of baker's yeast by simple diffusion (no effect of inhibitors and a linear concentration dependence of the initial rate of uptake and final distribution in cells). It distributes itself in 96.6 +/- 16.2% of intracellular water.

Cited by 20 publications

References 4 publications

Intracellular ethanol — accumulation and exit from yeast and other cells

Intracellular ethanol — accumulation and exit from yeast and other cells

Physiology of yeasts in relation to biomass yields

Enzyme identification and development of a whole‐cell biotransformation for asymmetric reduction ofo‐chloroacetophenone

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