Methanol and ethanol utilization in methylotrophic yeast Pichia pinus wild-type and mutant strains

In the wild-type strain of methylotrophic yeast Pichia pinus diauxic growth is observed during cultivation in medium containing a mixture of methanol and ethanol: firstly, slow phase of ethanol utilization is revealed and, secondly, a fast phase of methanol consumption is shown. Diauxic growth is observed also in ecr1 mutant, impaired in ethanol-induced catabolite repression of methylotrophic metabolism enzymes, but the order of utilization of the alcohols is inverted in this mutant. Such succession of alcohols utilization in both strains correlates well with the sequence of synthesis of microbody enzymes which catalyze key reactions of C₁- and C₂-metabolism. On the contrary, simultaneous utilization of methanol and ethanol from the mixture, as well as synchronous synthesis of both peroxisomal and glyoxisomal enzymes is observed in adh1 mutant which has reduced alcohol dehydrogenase activity. The strong differences between the wild-type strain and adh1 mutant were observed also in the kinetics of specific activity changes for C₁-metabolizing enzymes, localized in cytosol. In the wild-type strain during growth on methanol and ethanol mixture such changes correlate with the sequence of alcohol utilization. At the same time, in adh1 mutant the activities of formaldehyde dehydrogenase and formate dehydrogenase during the growth on the alcohols mixture are as high as during growth on methanol only, but the activity of dihydroxyacetone kinase is as low as under the growth on ethanol and is lower than on methanol.