Effect of increasing methanol concentrations on physiology and cytology of Candida boidinii

Concentration of methanol in the medium strongly affected not only the physiology but also the cytology of Candida boidinii strain 2 cells in a methanol-limited chemostat at a constant dilution rate D 0.1/h and at low pH 3.0. The formation of large cubic peroxisomes with high alcohol oxidase (AO) activity observed at low methanol concentration (S0 3 g/L) disappeared on increasing the methanol concentration in the inflow medium. The AO activity in the cells sharply decreased, followed by accumulation of riboflavin phosphate and residual methanol in the medium. The activity of catalase was relatively stable. At methanol concentration S0 > KI (KI equal to 12 g methanol per L), which included a substantial increase in methanol dissimilation, documented by higher formaldehyde and formate dehydrogenase activities and by lower yield coefficient on methanol, the yeast cells contained large lobe-shaped peroxisomes and a smaller number of larger mitochondria. The cells formed pseudomycelium with a thick septum between the mother and daughter cells.