Biosynthesis of Citric Acid from Glucose–Fructose Syrups by the Yeast Yarrowia lipolitica

Glucose–fructose syrups were studied for the first time as a carbon source for the biosynthesis of citric acid (CA) by the yeast Yarrowia lipolytica. The producer Y. lipolytica VKM Y-2373 was selected, and the growth conditions were optimized (syrup concentration, 30 g/L; pH, 6.0; aeration, 20% of saturation). The study found that the concentration of ammonium sulfate in the medium had a significant impact on CA production by Y. lipolytica. The maximum CA production was observed at a concentration of 2 g/L (NH4)2SO4, while concentrations of 1.5 and 3.0 g/L resulted in a decrease of 12 and 30%, respectively. Under the selected conditions, Y. lipolytica VKM Y-2373 produced 36.7 g/L CA in a medium containing glucose–fructose syrup with 52% glucose and 57.7 g/L CA with syrup containing 92% glucose.