Describe the mechanism of fermentation in the presence of yeast and lactic acid bacteria ?

Explanation

The first step of anaerobic respiration is glycolysis, in which glucose is incompletely oxidised to 2 pyruvic acid moecules with 2ATP and 2`NADH_(2)` formed as by-products.
Pyruvic acid formed is used for alcoholic fermentation or lactic acid fermentation.
In alcoholic fermentation, the pyruvic acid is first decarboxylated to actaldehyde liberating `CO_(2)`. Later acetaldehyde is reduced to ethyl alcohol by `NADH_(2)` of glycolysis.
This process occurs in anaerobes like yeast and bacteria.
In lactic acid fermentation, the pyruvic acid is directly reduced to lactic acid by `NADH_(2)` of glycolysis. NO `CO_(2)` is liberated. It occurs in lacto bacilli, and skeletal muscles.