Answer: Lactobacillus.
- A Aspergillus niger
- B Saccharomyces cerevisiae
- C Lactobacillus
- D Rhizobium
Correct answer: C. Lactobacillus
Explanation: Lactobacillus carries out lactic acid fermentation, converting sugars to lactic acid, used in curd and cheese making.
Sewage passes through physical removal (primary), then aerobic biological treatment where microbes form flocs that consume organic matter (secondary); the settled activated sludge is then digested anaerobically to produce biogas - a deliberate switch from aerobic to anaerobic conditions between stages.
Concept context
Microorganisms in food, medicine, sewage treatment, biocontrol, and biofertilizers