Oxidation of exogenous formaldehyde in methylotrophic and nonmethylotrophic yeast cells.

Nonmethylotrophic (Candida maltosa and Saccharomyces cerevisiae) and methylotrophic (Hansenula polymorpha) yeast cells acidified their incubation media in the presence of formaldehyde. This was associated with the release of formate. We studied the formaldehyde-dependent production of formic acid and the enzymatic properties of these strains grown on media containing various carbon sources. The acidifying potential was considerably lower in formaldehyde dehydrogenase-deficient cells of mutant strains of H. polymorpha. The rates of acidification by C. maltosa and S. cerevisiae depended on the activity of their nonspecific aldehyde dehydrogenases. We suggest that accumulation of formate by yeast cells incubated in the presence of formaldehyde is caused by the total activity of formaldehyde dehydrogenase and nonspecific aldehyde dehydrogenase in methylotrophic yeasts or aldehyde dehydrogenase only in nonmethylotrophic yeasts. This is probably an additional mechanism for detoxification of formaldehyde.