NEET 2025 MCQ with Answer Explanation : Microbes in Human Walefare.

71. Which of the following microbes is used in making the traditional Japanese food “Natto”?
    A. Bacillus subtilis
    B. Saccharomyces cerevisiae
    C. Lactobacillus bulgaricus
    D. Penicillium roqueforti

Answer: A. Bacillus subtilis

Explanation:
Natto is made by fermenting soybeans using Bacillus subtilis, which gives the food its characteristic texture and flavor.

72. The bacterium that converts alcohol to acetic acid in vinegar production is:
    A. Saccharomyces cerevisiae
    B. Lactobacillus
    C. Acetobacter aceti
    D. Penicillium notatum

Answer: C. Acetobacter aceti

Explanation:
Acetobacter aceti converts ethanol (alcohol) into acetic acid during the production of vinegar, a process of aerobic fermentation.

73. A biofertilizer commonly used in paddy fields for nitrogen fixation is:
    A. Streptococcus
    B. Anabaena
    C. Clostridium
    D. Penicillium

Answer: B. Anabaena

Explanation:
Cyanobacteria like Anabaena fix atmospheric nitrogen in the soil, providing an essential nutrient for plants, particularly in paddy fields.

74. The fungal species used in the ripening of blue cheese is:
    A. Penicillium roqueforti
    B. Rhizopus nigricans
    C. Saccharomyces cerevisiae
    D. Aspergillus oryzae

Answer: A. Penicillium roqueforti

Explanation:
Penicillium roqueforti is responsible for the characteristic blue veins in blue cheese, contributing to its flavor and texture.

75. Azotobacter is known for:
    A. Fermenting alcohol
    B. Fixing nitrogen in legume root nodules
    C. Fixing atmospheric nitrogen in soil
    D. Producing antibiotics

Answer: C. Fixing atmospheric nitrogen in soil

Explanation:
Azotobacter is a free-living nitrogen-fixing bacterium that improves soil fertility by converting atmospheric nitrogen into a form that plants can use.

76. The bacterium used for bioremediation of oil spills is:
    A. Pseudomonas putida
    B. Rhizobium
    C. Penicillium
    D. Lactobacillus

Answer: A. Pseudomonas putida

Explanation:
Pseudomonas putida can break down and degrade hydrocarbons in oil, making it useful for bioremediation of oil spills and other petroleum-based pollutants.

77. Which of the following microbes is involved in the production of bioethanol?
    A. Saccharomyces cerevisiae
    B. Clostridium botulinum
    C. Escherichia coli
    D. Rhizopus stolonifer

Answer: A. Saccharomyces cerevisiae

Explanation:
Saccharomyces cerevisiae ferments sugars into ethanol, which is used in bioethanol production, a renewable energy source.

78. The bacterium involved in converting milk to yogurt is:
    A. Lactobacillus acidophilus
    B. Escherichia coli
    C. Bacillus subtilis
    D. Penicillium notatum

Answer: A. Lactobacillus acidophilus

Explanation:
Lactobacillus acidophilus is a key bacterium in yogurt production, fermenting lactose to produce lactic acid, which thickens the milk and gives yogurt its tangy flavor.

79. The fungus used in brewing soy sauce is:
    A. Rhizopus
    B. Aspergillus oryzae
    C. Penicillium
    D. Saccharomyces cerevisiae

Answer: B. Aspergillus oryzae

Explanation:
Aspergillus oryzae is used in the fermentation process of soybeans and wheat to produce soy sauce, an essential component in Asian cuisine.

80. Which microorganism is used to produce vitamin C (ascorbic acid) industrially?
    A. Gluconobacter oxydans
    B. Lactobacillus bulgaricus
    C. Saccharomyces cerevisiae
    D. Rhizopus stolonifer

Answer: A. Gluconobacter oxydans

Explanation:
Gluconobacter oxydans is used in the industrial production of vitamin C, converting sorbitol into sorbose, a precursor in ascorbic acid synthesis.