OXIDATION OF EXOGENOUS FORMALDEHYDE IN METHYLOTROPHIC AND NONMETHYLOTROPHIC YEAST-CELLS

Nonmethylotrophic (Candida maltosa and Saccharomyces cerevisiae) and m ethylotrophic (Hansenula polymorpha) yeast cells acidified their incub ation media in the presence of formaldehyde. This was associated with the release of formate. We studied the formaldehyde-dependent producti on of formic acid and the enzymatic properties of these strains grown on media containing various carbon sources. The acidifying potential w as considerably lower in formaldehyde dehydrogenase-deficient cells of mutant strains of H. polymorpha. The rates of acidification by C. mal tosa and S. cerevisiae depended on the activity of their nonspecific a ldehyde dehydrogenases. We suggest that accumulation of formate by yea st cells incubated in the presence of formaldehyde is caused by the to tal activity of formaldehyde dehydrogenase and nonspecific aldehyde de hydrogenase in methylotrophic yeasts or aldehyde dehydrogenase only in nonmethylotrophic yeasts. This is probably an additional mechanism fo r detoxification of formaldehyde.