Journal article

Metabolic uncoupling in Saccharomyces cerevisiae

Aerobic chemostat cultures of S. cerevisiae were performed at different diln. rates under energy (glucose) limitation or at various extents of energy excess imposed by a N limitation. Energy excess induced metabolic uncoupling under steady-state conditions. The sp. EtOH prodn. rate was always higher the lower the feed medium N concn. throughout the whole range of diln. rates tested. In addn., the respiratory rate also increased under N limitation, for at least as long as the sp. O2 consumption rate was below the max. capacity. These results imply that the ATP yield (YATP in g biomass per mol ATP) and/or the amt. of ATP produced, i.e. the P/O ratio, must be able to change. By assuming a const. YATP of 16 g/mol, a decrease in the P/O ratio from 1 to 1.5 at low diln. rates and glucose limitation down to only 0.1-0.2 at high diln. rates and N limitation could be calcd. If, instead, a fixed P/O ratio of 1.0 was assumed, the YATP decreased from .apprx.20 down to <10 g/mol during these different conditions. The heat yield values, i.e., the amt. of heat produced per amt. of biomass formed, increased dramatically when the cells were subjected to a N limitation, indicating less efficient growth in terms of conserving substrate energy as biomass under energy excess compared to energy-limiting conditions. [on SciFinder (R)]


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