These organisms, called sulfur reducers , play a role in the sulfur cycle. Sulfate is reduced to hydrogen sulfide gas. B. Fermentation - This type of anaerobic metabolism uses no electron transport chain . Fermentation generates fewer ATP per molecule of substrate. Because many molecules of substrate must be metabolized to supply a cell's ATP requirements, the substrate must be in abundance in order for the microbe to grow.
Sugars are usually the only substrate that can be used in fermentation.
Pyruvic Acid Oxidation - pyruvic acid is oxidized to lactic acid using NADH, thus using up the reducing power stored in glycolysis. This type of fermentation is typical of yeast, a type of fungi. In this pathway, pyruvic acid is converted to carbon dioxide and ethanol. Return to Chp.