Oxidation of methanol, formaldehyde and formic acid by methanol-utilizing yeast

Methanol-utilizing yeast, Candida boidini 11 Bh, characterized by high tolerance to methanol during growth, displays even higher tolerance when the oxidation rate by intact cells is tested. Low respiration activity is found even at 22% v/v of methanol. The half-saturation constant was 17-18 mM. The half-saturation constants for the two oxidation intermediates, formaldehyde and formic acid were 3.5-4.0 an .d 30-33 mM, respectively. When applied together with standard concentration of methanol, very low concentrations of both intermediates stimulated the oxidation rate. These results are discussed in connection with the relationship between growth and oxidation, the tolerance to high concentrations of inhibitory products and the mechanism of inhibition.