Use of microorganisms in industry and agriculture — A/L Biology

How do I practise Use of microorganisms in industry and agriculture?

1 question with a worked solution

1. Which filamentous fungus is industrially cultivated under submerged aerobic conditions on carbohydrate substrates for the commercial production of citric acid?
   1. A) Aspergillus niger
   2. B) Saccharomyces cerevisiae
   3. C) Penicillium chrysogenum
   4. D) Rhizopus stolonifer
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   Correct answer: A) Aspergillus niger

   Aspergillus niger is the primary industrial organism for citric acid production. When grown on high-sugar media (such as beet or cane molasses) with limited iron and manganese at low pH (<2.5), its Krebs cycle is overflowed, causing massive excretion of citric acid.

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   Step 1: Match industrial microbes to products: - Penicillium chrysogenum: Penicillin antibiotic. - Saccharomyces cerevisiae: Ethanol and bread baking. - Rhizopus stolonifer: Fumaric acid and steroid bioconversions. - Aspergillus niger: Citric acid and gluconic acid. Answer: Aspergillus niger.
   Modelled on: the A/L Biology examination pattern

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Where does Use of microorganisms in industry and agriculture fit in the syllabus?

Year 2 · Term 3