ENOLOGICAL FERMENTATION KINETICS OF AN ISOGENIC PLOIDY SERIES DERIVEDFROM AN INDUSTRIAL SACCHAROMYCES-CEREVISIAE STRAIN

We used a heat-induced endomitotic polyploidization procedure to const ruct an isogenic ploidy series (2N to 4N) from an industrial strain of Saccharomyces cerevisiae. The nature of the yeast ploidy series obser ved in this work indicates that the physical and metabolic differences observed among the strains in the yeast ploidy series must be due to differences in gene dosage alone and not to heterosis. We then investi gated the fermentation kinetics of the yeast ploidy series on simulate d standard grape juice under enological conditions. Cell specific CO2 production rates appeared to be as high as cell ploidy increases. Cell specific CO2 production rates relative to the cytoplasmic volume appe ared to be surprisingly different among strains within the ploidy seri es. We further related this phenomenon to the fact that cell specific CO2 production rates relative to cell plasma membrane surface areas we re equal for all the strains tested. The results obtained indicate tha t, although the normal balance of gene copy numbers was maintained for all enzyme-driven metabolic processes of strains within the ploidy se ries, a metabolic bottleneck seemed to occur at the plasma membrane le vel.