Valorization of raw glycerol for citric acid production by Yarrowia lipolytica yeast

In the present report, citric acid production from raw glycerol in two fed-batch systems by acetate negative-mutants of Yarrowia lipolytica: Wratislavia 1.31 and Wratislavia AWG7 was compared. In the system, in which the total glycerol concentration was 200 g.L(-1), the substrate was added by pulsed additions, and in the other, in which the total glycerol concentration was 300 g.L(-1), the substrate was added at a constant feeding rate of 1.4 g.h(-1). Despite high citric acid concentrations (155.2 and 157.5 g.L(-1) with Y. lipolytica Wratislavia 1.31 and Y. lipolytica Wratislavia AWG7, respectively) obtained from 300 g.L(-1) of glycerol, the yield of citric acid was similar, i.e. about 0.6 g.g(-1). The volumetric citric acid productivity was markedly higher (1.05 and 0.94 g.L(-1)h(-1) with Y. lipolytica Wratislavia 1.31 and Y. lipolytica Wratislavia AWG7 strains, respectively) in the cultures containing 200 g.L(-1) of carbon source.