SUMMARY: The effect of increasing concentrations of glucose and galactose on the physiology and composition of was studied in continuous culture. Glucose, at concentrations ranging from 1 to 50 g./l. was degraded predominantly by aerobic fermentation. Galactose catabolism was mainly aerobic at concentrations up to 5 g./l. but became increasingly fermentative at higher sugar concentrations. The fatty-acid content varied with the type of metabolism. Thus at low concentrations of sugar, fatty acids accounted for 8 % dry wt but about 5 % dry wt at high sugar concentrations. High sugar concentrations may be associated with the repression of mitochondrial structures.

The size of the amino acid pool was a function of the availability of ammonia in the medium. Such ‘pools’ contained appreciable amounts of arginine when NH+ was in excess, whereas in the absence of NH+ from the culture filtrate only trace amounts of arginine were detected. The content of glutamic dehydrogenase in the yeast varied directly with the availability of ammonia and the size of the amino acid pool.


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