Yeasts sugar utilization

Hexokinase is of great biological interest since it would appear that not only in yeast cells but in most, if not all, plant and animal cells phosphorylation at C6 of the common hexoses D-glucose, D-fructose and D-mannose initiates sugar utilization. Since on solution in water the crystalline hexoses quickly undergo mutarotation, resulting in an equilibrium mixture of various tautomeric modifications, the fermentability... 

In certain instances, the exocellular and intracellular polysaccharides of yeasts have been used by taxonomists as an aid in classification of the parent organisms. For example, Lipomyces lipoferus may readily be distinguished from Lipomyces starkeyi by the sugars formed on partial and on complete hydrolysis of their exocellular polysaccharides (see Table VII), a differentiation that is difficult if morphological characteristics and sugar-utilization patterns are used. ... 

The ability of yeasts to utilize sugars is not only of potential value it can also be a nuisance.25,26 Yeasts are notorious as spoilers of foods that contain a high concentration of one or more sugars, such as honey, maple syrup, sugar cane, and confectionery. The capacity of the yeasts Saccharomyces bisporus and Saccharomyces rouxii to ferment honey,27,28 which is composed of 70 to 80% of hexoses,29 is a feat of outstanding physiological interest in view of the remarkably high osmotic forces which the yeasts must withstand.30-32... 

Many yeasts can utilize certain sugars and derivatives of sugars anaerobically. This anaerobic utilization is here called fermentation. The formation of gas, presumably carbon dioxide, is usually the most obvious sign of fermentation. 

Abilities of 434 Species of Yeast to Utilize Sugars and their Derivatives Aerobically or Anaerobically 1... 

Kuyper, M., Toirkens, M. J., Diderich, J. A., Winkler, A. A., Van Dijken, J. R, Pronk, J. T. (2005). Evolutionary Engineering of mixed-sugar utilization by a xylose-fermenting Saccharomyces cerevisiae strain. FEMS Yeast Research, 5, 925-934. 

The yeasts exhibited a similar sugar utilization pattern (data not shown). Glucose and xylose were assimilated simultaneously, the former at a higher rate, enabling higher growth rates. Xylose was completely assimilated by P. stipitis and D. hansenii, but not by K. marxianus, which only consumed 70%. Arabinose was also assimilated by all yeasts simultaneously with late xylose assimilation, being only completely exhausted by D. hansenii. The other two yeasts, Pichia stipitis and K. marxianus, only consumed 31 and 45% of available arabinose, respectively. Furfural, acetic, and formic acid were also consumed (data not shown). 

D Amore, T., Russell, 1., Stewart, G. G. (1989). Sugar utilization by yeast during fermentation. Journal of Industrial Eermentation, 4, 315-344. 

Owen (99) studied the effect of bacterial contaminants on the efficiency of sugar utilization by yeast in molasses fermentations. His results did not yield a clear-cut indication that the contaminants were always harmful. Fluorides as antiseptics improved the efficiency in heavily contaminated mashes. However, they also had a beneficial effect in the same mashes sterilized by heat before seeding. The conclusion is that the effect of contaminants depends on the stage at which they are introduced and on the effect per se of the countermeasures taken. It must be borne in mind that other factors than the mere killing of the bacteria enter the picture. These other factors may themselves alter the course of the fermentation and thus make interpretation difficult. 

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