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Food Science and Technology QUESTION #5876
Question 1
In yoghurt fermentation, \(S.\; thermophilus\) and \(L.\; bulgaricus\) exhibit a symbiotic relationship. Which statement correctly describes this?
  • Both organisms produce only lactic acid independently
  • \(S.\; thermophilus\) produces \(\text{CO}_2\) stimulating \(L.\; bulgaricus\); \(L.\; bulgaricus\) produces amino acids stimulating \(S.\; thermophilus\)
  • \(L.\; bulgaricus\) grows first and lowers \(\text{pH}\) enabling \(S.\; thermophilus\)
  • \(S.\; thermophilus\) produces formic acid and \(\text{CO}_2\) stimulating \(L.\; bulgaricus\); \(L.\; bulgaricus\) proteolysis releases peptides stimulating \(S.\; thermophilus\) growth✔️
Correct Answer Explanation
This is protocooperation: \(S.\; thermophilus\) grows first producing formic acid and \(\text{CO}_2\) stimulating \(L.\; bulgaricus\). \(L.\; bulgaricus\) then produces protease activity releasing peptides and amino acids (valine, histidine) that stimulate further \(S.\; thermophilus\) growth.