Final answer:
Lactobacillus uses homolactic fermentation to produce lactic acid from pyruvate, regenerating NAD+ from NADH. This process is crucial in yogurt production and happens under anaerobic conditions, where oxygen is scarce or absent.
Step-by-step explanation:
Lactic Acid Fermentation in Lactobacillus
Lactic acid is produced during the fermentation process by Lactobacillus in the production of yogurt. This type of fermentation is known as homolactic fermentation, where pyruvate is reduced to lactic acid, regenerating NAD+ from NADH in the process. The reaction is as follows: Pyruvate + NADH → lactic acid + NAD+. The production of lactic acid not only contributes to the acidic environment necessary for yogurt production but also has implications in food safety and health, such as inhibiting the growth of pathogens.
In this specific context, the correct answer to the question is: a. fermentation....NAD+ because Lactobacillus uses fermentation to convert lactose into lactic acid, regenerating NAD+ which is then available to keep the glycolytic pathway operating to produce ATP for the cell. This pathway predominates when oxygen is scarce or absent and is typical of the muscle cells' response to intense activity as well as the function of red blood cells.