Yeasts anaerobic fermentation

Alcoholic Fermentation. Certain types of starchy biomass such as com and high sugar crops are readily converted to ethanol under anaerobic fermentation conditions ia the presence of specific yeasts Saccharomyces cerevisia and other organisms (Fig. 6). However, alcohoHc fermentation of other types of biomass, such as wood and municipal wastes that contain high concentrations of cellulose, can be performed ia high yield only after the ceUulosics are converted to sugar concentrates by acid- or enzyme-catalyzed hydrolysis ... 

Product formation stoichiometry can be used to estimate the upper bounds for product yields in processes. A relatively simple example is the anaerobic fermentation of glucose by yeast. Here, carbon dioxide and ethanol are the only products. Modification of (E -3.9) then becomes ... 

Anaerobic fermentation Water-l-sugar Carbon dioxide Yeast... 

Bauer and co-workers (Rottenbacher, 1985 Rottenbacher et ah, 1987) carried out anaerobic fermentation under nitrogen gas at 18-20°C in a gas-tight closed circuit with a partial condenser followed by a gas adsorber for ethanol and water vapour recovery. The highest rate of ethanol production was about 50gh with a bed of 2.4 kg of extruded cylindrical baker s yeast pellets of diamefer 800 rm. This rate is less... 

If energy is generated solely by substrate-level phosphorylation, as with anaerobic fermentative metabolism of bacteria and yeast, then the yield is more tightly linked to the amount of energy generated. Generally 10 to 12 kg of cell dry matter can be synthesised per kmol of ATP generated in metabolism. 

FIGURE 1.1 Scheme of carbonic maceration winemaking. AM, anaerobic metabolism of grape berries YAF, yeast alcoholic fermentation M, maceration qd = pair temperature (q°C) action duration (days). (Figure from CEnologie—fondements scientifi-ques et techniques. Flanzy et al. collection Sciences Techniques Agroalimentaires. Technique Documentation, 1998, p. 780. Reproduced with the permission of the Editor.)... 

The anaerobic fermentation of sugars by Saccharomyces wine yeasts generates a variety of volatile metabolites that contribute to the sensory profile of wine. The important compounds include esters, higher alcohols, volatile fatty acids, carbonyls, and volatile sulfur compounds. The accumulation of these compounds in wine depends on the strain of yeast, must composition (chemical, physical and nutrient composition) and fermentation conditions. In addition, a variety of... 

In the anaerobic fermentation of grain, the yeast Saccharomyces cerevisiae digests glucose from plants to form the products ethanol and propenoic acid by the following overall reactions ... 

Biochemical reactions such as aerobic and anaerobic fermentations occur in the presence of living organisms or cells, such as bacteria, algae, and yeast. These reactions can be considered as biocatalyzed by the organism. Thus in a typical bioreactor a substrate (such as glucose) is fed into the fermenter or bioreactor in the presence of an initial amount of cells. The desired product can be the cells themselves or a secreted chemical called a. metabolite. In either case the cells multiply in the presence of the substrate, and the rate of production of cells is proportional to the concentration of the cells— hence this process is autocatalytic. In a batch reactor with ample... 

Over half the known species of yeasts can ferment D-glucose anaerobically (see Table III). Saccharomyces cerevisiae ferments both a- and /3-D-glucopyranose at about the same rate.176 In the anaerobic fermentation of sugars, yeasts convert the pyruvate produced by glycolysis into ethanol by way of acetaldehyde. 

Only a few yeasts and bacteria are able to spoil wine, because of the high sugar content, low pH, high alcohol concentrations, and anaerobic fermentation conditions (Du Toit, Pretorius, and Lonvaud-Funel, 2005). 

Yeast cells ferment the sugars in fruits to produce ethanol and carbon dioxide. The anaerobic process must be carried out in tightly sealed containers such as these large tanks. One-way valves allow carbon dioxide to escape from the fermenting liquid without letting air in. ... 

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