Yarrowia lipolytica yeast is well known to be able to synthesize citric acid (CA) in large amounts. This study deals with CA biosynthesis, the production of biomass, as well as the accumulation and composition of proteins and lipids in Y. lipolytica VKM Y-2373 grown in media with glucose at different concentrations of ammonium sulfate (from 2 to 10 g/L). It was found that these concentrations of nitrogen source are limiting for the growth of Y. lipolytica and that nitrogen deficiency is the main cause of CA excretion. At the high concentration of (NH4)2SO4 (10 g/L), the accumulation of cell biomass, biomass yield (YX/S), and protein concentration was higher than in the medium with 2 g/L ammonium sulfate by 4.3 times, 143%, and 5.1 times, respectively. CA was accumulated in meaningful quantities only in media containing 3-10 g/L (NH4)2SO4 with the maximum concentration of CA (99.9 g/L) at 4 g/L ammonium sulfate. Also of interest is the technological mode with 6 g/L (NH4)2SO4, which is characterized by high productivity (1.11 g/L × h). It should be noted that biomass contains large amounts of essential amino acids and unsaturated fatty acids and can be used in food biotechnologies and agriculture.
Keywords: Yarrowia lipolytica; biomass production; citric acid (CA) production; fermentation; glucose; microbial synthesis; nitrogen limitation; yeast biochemistry; yeast lipids; yeast protein.