Final answer:
Lactic acid fermentation involves the reduction of pyruvate to lactic acid, used by muscles under low oxygen conditions and by certain bacteria in food production.
Step-by-step explanation:
Lactic acid fermentation is a biological process by which pyruvate from glycolysis is reduced to lactic acid by NADH, regenerating NAD+ in the process. This type of fermentation is carried out by the muscles during intense activity when there is an insufficient oxygen supply, as well as by various bacteria involved in the production of fermented foods such as yogurt and cheese.
In particular, bacteria of several gram-positive genera, including Lactobacillus, Leuconostoc, and Streptococcus, also known as lactic acid bacteria (LAB), play a crucial role in food production. The lactic acid produced during this fermentation process not only contributes to the sour taste of these foods but also helps preserve them by creating an acidic environment which inhibits the growth of spoiling agents.
During strenuous exercise, muscles use lactic acid fermentation for energy when oxygen supply is low, leading to the build-up of lactic acid. This was once believed to cause muscle soreness, although recent research contradicts this. Nonetheless, lactic acid is an important intermediate and is transported to the liver through blood circulation for further metabolism, demonstrating lactic acid's essential role in both human physiology and food technology.