Question

The end product of the fermentation of sugars by Lactobacillus bacteria is
a. Lactic acid
b. $C{O_2}$
c. Methyl alcohol and $C{O_2}$
d. Butyl alcohol

Answer 1

Hint: Lactobacillus are nonmotile and can survive in both aerobic and anaerobic environments. The amount of lactic acid that is produced by different Lactobacillus organisms varies. Lactobacillus are commensal inhabitants of animal and human gastrointestinal tracts.

Complete answer:
Anaerobic respiration is the chemical breakdown of glucose in the absence of oxygen is called fermentation. The intermediate product produced is pyruvate followed by oxidation of NADH and formation of lactic acid. The bacterium Lactobacillus is used for the production of lactic acid.
Fermenting bacteria are obligate anaerobes, use a variety of organic substrates like alcohols, sugars, and organic and amino acids, and convert them into $C{O_2}$. The process of fermentation occurs inside microbial cells and does not require an external supply of electron acceptors.

Other given options from question are:
- $C{O_2}$ is used by some organisms to carry out respiration.
- Methyl alcohol and $C{O_2}$ are used as a solvent and are used to create fuel.
- Butyl alcohol is produced by the fermentation of biomass by Clostridium bacteria.

Hence, the correct answer is option (A).

Additional information:
During the process, ATP is produced by substrate-level phosphorylation. These bacteria are rod-shaped, gram-positive, non-spore-forming bacteria of the family Lactobacillaceae. The lactic acid bacteria belong to Lactobacilli and comprise the major part of this group. Lactic acid bacteria perform an essential role in the preservation and production of wholesome foods.

The lactic acid bacteria consist of the homo fermenters and the hetero fermenters. Homo fermenters produce lactic acid, via the glycolytic pathway. Hetero fermenters produce lactic acid, ethanol, acetate, and carbon dioxide.
- Homolactic fermentation: 1 mole of glucose yields two moles of lactic acid.
- Heterolactic fermentation: 1 mole of glucose yields 1 mole each of lactic acid, ethanol, and carbon dioxide.

Note: Lactic acid bacteria are obligate anaerobes, non-respiring, and gram-positive. They carry out the conversion of carbohydrate to lactic acid plus carbon dioxide and other organic acids without the need for oxygen. Lactobacillus is used for the production of lactic acid. These bacteria are used in the preservation of various food products. In lactic acid fermentation, little or no heat is required in their preparation, making them fuel-efficient.