The effect of temperature on the fermentation of d-mannose by yeast

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Abstract
In contrast to that of d-glucose, the temp. coeff. of d-mannose fermentation by yeast cells is dependent on substrate conc.; it increases considerably with decreasing man-nose conc. With yeast extract as fermenting agent, no such difference between mannose and glucose is observed. It would thus appear that the cell membrane is responsible for this phenomenon. The maximum rates of mannose and glucose fermentation at 25[degree] by yeast extract are the same provided that during the prepn. of the yeast extract the temp. does not exceed 28[degree]; with higher temps. mannose is fer-mented markedly slower than glucose. Taken with previous findings of Jephcott and Robinson (Biochem. Jour. 28: 1844. 1934) this result suggests the existence in yeast of 2 aldo-hexose phosphate isomerases, the mannose-6-phosphate isomerase being more readily destroyed at 28-38[degree] than the glucose-6-phosphate isomerase. Expts. at 10[degree] afford evidence that both a-and d-mannopyranose are fermented without preliminary interconversion by mutarotation.