Light stimulated 'shunt-metabolism' succinate-alpha-ketoglutarate-isocitrate cycle and accumulation of citric acid in Aspergillus niger.

Studies with light of the visible range had shown that light plays significant role in the biosynthesis and accumulation of citric acid in Aspergillus niger. Accumulation of 14C-labelled carbon atoms in alpha-ketoglutaric, isocitric, succinic and glycolic acids in the cultures grown under illumination suggest a probable 'shunt-metabolism' leading to the succinate-alpha-ketoglutarate-isocitrate (SKI) cycle. This shunt metabolism minimizes the accumulation of citric acid in cultures due to depletion of intermediates.