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Using Yarrowia lipolytica (DS‐1), secretion of citric acid is studied as a function of carbon sources such as glucose, fructose, hydrol, sucrose, cane sugar molasses, kerosene (all available commercially) and tapioca starch hydrolysate, invert sucrose and invert cane sugar molasses (all prepared in laboratory). On the basis of their acceptability by DS‐1 for citric and isocitric acid secretion, it is concluded that (a) sucrose and cane sugar molasses (with/without inversion) served as poor carbon sources, (b) fructose, hydrol, impure tapioca starch hydrolysate (96 DE w/w) and invert sucrose served as relatively better carbon sources and (c) purified tapioca starch hydrolysate (96 DE w/w) was the best carbon source to substitute glucose by giving comparable (75%) efficiency of conversion and economical advantage.

Waste liquor from caprolactam manufacture contains many mono- and di-carboxylic acids. Of four yeasts tested, Yarrowia lipolytica DS-1 was the best at decreasing Chemical Oxygen Demand values, by up to 60% with 50 and 100 g waste liquor/after 48 h. Caproic, butyric and valeric acids were utilized most easily. Adipic acid was not decreased below 13% (w/v).