Answer: Saccharomyces cerevisiae.
- A Lactobacillus
- B Aspergillus niger
- C Saccharomyces cerevisiae
- D Rhizobium
Correct answer: C. Saccharomyces cerevisiae
Explanation: Saccharomyces cerevisiae (bakers yeast) ferments sugars to produce CO2 which causes bread to rise.
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