[Variability in the flavinogenic activity of Pichia guilliermondi yeasts]

The natural and induced variability of the flavinogenic activity was studied in the strain of Pichia guilliermondii ATCC 9058. The flavinogenic activity of the collection strain showed normal distribution; the amount of riboflavin(RF) accumulated in the medium differed several times in the extreme variants. In the clones with the maximum and minimum accumulation of RF, the distribution of the variants was asymmetric, due to the appearance of the cells with an average flavinogenic activity. The clones have acquired almost the same flavinogenic activity after being transferred eight times on a fresh medium. The asymmetric distribution of the variants according to their flavinogenic activity was found also in the case of the clones obtained from the UV-irradiated cells. The mutants have been isolated, which synthesized 3-30 times more RF than the parent strain in the presence of iron doses optimal for the growth. Five mutants that were most active in producing RF differed in the sensitivity of their flavinogenesis to high concentrations of iron, yeast autolysate, and carbon sources.