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In anaerobic conditions, this enzyme participates in the fermentation process that occurs in yeast, especially of the genus Saccharomyces, to produce ethanol by fermentation. It is also present in some species of fish (including goldfish and carp ) where it permits the fish to perform ethanol fermentation (along with lactic acid fermentation ...
Yeast need a reliable source of nitrogen in forms that they can assimilate in order to successfully complete fermentation. Yeast assimilable nitrogen or YAN is the combination of free amino nitrogen (FAN), ammonia (NH 3) and ammonium (NH 4 +) that is available for a yeast, e.g. the wine yeast Saccharomyces cerevisiae, to use during fermentation.
Despite the bactericidal effects of ethanol, acidifying effects of fermentation, and low oxygen conditions of industrial alcohol production, bacteria that undergo lactic acid fermentation can contaminate such facilities because lactic acid has a low pKa of 3.86 to avoid decoupling the pH membrane gradient that supports regulated transport. [7]
Microbial food cultures are live bacteria, yeasts or moulds used in food production. Microbial food cultures carry out the fermentation process in foodstuffs. Used by humans since the Neolithic period (around 10 000 years BC) [1] fermentation helps to preserve perishable foods and to improve their nutritional and organoleptic qualities (in this case, taste, sight, smell, touch).
Moreover, the presence of either salt or sugar has a positive effect on the ability of Z. bailii to initiate growth at extreme pH levels, e.g. the yeast showed no growth at pH 2.0 in the absence of NaCl and sucrose, but grew at this pH in 2.5% (w/v) NaCl or 50% (w/v) sucrose. [26]
Fermentation is another core aspect of their chemical activity and how they obtain energy, but they only perform alcoholic fermentation and do not produce lactic acid. [10] Some species cannot assimilate potassium nitrate as a sole nitrogen source, [ 3 ] but all maintain the potential to nitrify ammonium to nitrate in vitro . [ 12 ]