PRODUCTION AND PROPERTIES OF 2,3-BUTANEDIOL: XXXII. 2,3-BUTANEDIOL FERMENTATIONS AT POISED HYDROGEN ION CONCENTRATIONS

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Abstract
The anaerobic dissimilation of glucose by Bacillus polymyxa, B. subtilis (Ford''s type), Aerobacter aerogenes, and Serratia marcescens was studied at poised H-ion concns. covering the range pH 5-8. Each fermentation was controlled within [plus or minus] 0.05 pH units by automatic addition of NH4OH solns. The H-ion concn. had a marked effect, similar for all organisms, on the overall rate of dissimilation and the relative yield of products. The time required to completely ferment a medium containing 5% glucose varied from 22 hrs. for B. subtilis to 9.5 hrs. for A. aerogenes at the optimum pH, which was within the range 7-7.6. The yield of 2,3-butanediol decreases above pH 6.4, until above pH 7.6 little or none is formed, although fairly rapid breakdown of glucose is still obtained. At the same time the yield of acetoin tends to increase; there is little change in the amt. of ethanol formed. The yields of acetic and lactic acids increase markedly in alkaline media, the latter showing an optimum at pH 7.6. A pronounced decrease in the yields of CO2 and H2 occurs above pH 7 and is accompanied by an approx. equal increase in the yield of formic acid, which rises from 0.3-120 millimoles per 100 millimoles of glucose dissimilated in the A. aerogenes fer-mentation.

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