GLUCOSE-METABOLISM, ENZYMATIC ANALYSIS AND PRODUCT FORMATION IN CHEMOSTAT CULTURE OF HANSENIASPORA-UVARUM

The physiology of Hanseniaspora uvarum K-5 was studied in glucose-limi ted chemostat cultures and upon glucose pulse. Up to a dilution rate o f 0.28 h(-1), glucose was completely metabolized in biomass and CO2. A bove this value, increase in the dilution rate was accompanied by sequ ential production of metabolites (glycerol, acetate and ethanol) and d ecrease in cell yield. Similar results were observed upon glucose puls e. From the enzyme activities (pyruvate dehydrogenase, pyruvate decarb oxylase, NAD and NADP-dependent acetaldehyde dehydrogenases, acetyl co enzyme A synthetase and alcohol dehydrogenase) and substrate affinitie s, the following conclusions were drawn with respect to product format ion of cells: (1) pyruvate was preferentially metabolized via pyruvate dehydrogenase, when biomass and CO2 were the only products formed; (2 ) acetaldehyde formed by pyruvate decarboxylase was preferentially oxi dized in acetate by NADP-dependent aldehyde dehydrogenase; acetate acc umulation results from insufficient activity of acetyl-CoA synthetase required for the complete oxidation of acetate; (3) acetaldehyde was o xidized in ethanol by alcohol dehydrogenase, in addition to acetate pr oduction.