[Effect of cultivation conditions on growth of Candida lipolytica yeasts and alpha-ketoacid biosynthesis in the presence of thiamine deficiency].

The effect of pH and aeration on the growth of Candida lipolytica and the biosynthesis of alpha-keto acids on acetate and glucose was studied in batch cultures at thiamine deficiency. If the initial thamine concentration was the same, then, irrespective of the carbon source, the yeast biomass in a medium saturated with oxygen by 5--10% was 1.5--2.0 times higher than in a medium with 60--90% [O2]. The rate of alpha-keto acid biosynthesis, on the contrary, decreased in the conditions of low aeration. The biomass increased and the rate of acid production decreased when pH was changed from 6.0 to 8.0 in a medium with acetate. However, at all studied values of pH and [O2] in a medium with either acetate or glucose, the growth at the deceleration phase was of a linear character, and was accompanied with the accumulation of alpha-keto acids in the cultural broth. The rate of acid production was maximal when the specific growth rate decreased to 0.04--0.06 hr-1. The presence of a linear phase in the conditions of thiamine deficiency suggests that here the growth of yeasts is determined by the constant activity of one of the thiamine dependent enzymes per unit volume of the cultural broth. However, the value of this activity seems to change depending on the cultivation conditions which, in turn, causes changes in the rates of biosynthetic processes.