Question

in stoichiometric equation for molasses fermentation, there's ammonia (nh3) which is the source for nutrient for yeast to grow. Is it possible that yeast cell absorb nh3 instead of nh4? I know that nh3 gas is soluble in water, but shouldn't all nh3 be converted to nh4oh by hydrolysis?

Answer 1

Yes, the ammonia is undoubtedly converted to ammonium ions on hydrolysis.

• Yeast contains a compound called alpha-ketoglutarate that actively react with amino acids or ammonium to form glutamate.
• The glutamate is converted to glutamine by the enzyme glutamine synthetase.
• The glutamine is a key participant of the de novo of amino acid synthesis which is essential for yeast growth

Yeast maybe microscopic but they contain a lot of complex metabolic pathways that most cells also have. Read up on the de novo synthesis for exact details as it can be called an entire subject on its own.