The invertase positive Yarrowia lipolytica A-101-B56-5 strain was analyzed for simultaneous production of citric acid (CA) and invertase in four media of different composition. The analysis was carried out as bioreactor batch cultures with sucrose as carbon source. The highest CA concentration (157 g/L) was noted in medium A (250 g sucrose, 7.50 g NH₄Cl, 0.10 g KH₂PO₄, 5.00 g MgSO₄×7H₂O and 3.0 g yeast extract in 1 L). The yield of CA from consumed substrate reached 0.698 g/g, the volumetric productivity was 0.785 g/L/h and the specific production rate reached 0.018 g/g/h. In terms of invertase biosynthesis, the best medium was the rich medium D (150 g sucrose, 3.0 g yeast extract, 5.0 g malt extract and 5.0 g peptone in 1 L). The total invertase activity obtained in this medium reached 124 000 U/L. The final CA concentration in this medium was lower than in medium A, however, it presented the highest volumetric productivity (1.281 g/L/h), specific production rate (0.065 g/g/h) as well as the highest yield from biomass (4.704 g/g). This culture was also the shortest (72 h) among all tested processes. Surprisingly, the highest amount of secreted invertase (48.7%), calculated from the total invertase activity, was obtained for the process in medium A, and was six times higher than in the other media. This phenomenon was dependent on sucrose concentration, the accumulated biomass and the osmotic pressure of the medium.

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