AbstractFrom previous work, it was observed that during growth on mixtures of acetate and aldose sugars the growth yield of the bacteriumAcinetobacter calcoaceticuswas increased when aldonolactone hydrolysis occurred. In this paper, the underlying mechanism was investigated by studying the relationship between cellular yield and lactone hydrolysis in a quantitative way. The literature on the kinetics of acid formation from aldono‐lactones was reviewed. It appears that the reaction pattern is composed of lactone isomerization and hydrolysis steps which occur in series. In the acid pH range, lactone interconversion is the rate‐limiting step for acid formation, whereas above pH 7 hydrolysis is slowest. Only for D‐gluconolactone could the detailed mechanistic kinetics be evaluated. For a number of other aldonolactones, including D‐xylono‐ and D‐galactonolactone, an empirical kinetic equation was derived. The reaction rate constants of these lactones are much smaller than for gluconolactone. The kinetic model for the hydrolysis of xylonolactone was experimentally verified, by application of the electrical charge balance to measurement data from A.calcoaceticuscultures. Comparison of the published biomass yield data and the calculated rate of lactone hydrolysis revealed that they do not quantitatively agree. It can be concluded that the observed relation between biomass yield and lactone hydrolysis is only apparent. The results demonstrate the power of the electrical charge balance in the study of processes in which charged compounds are bein
展开▼
