EFFECT OF PH AND ACETIC-ACID ON GROWTH AND 2,3-BUTANEDIOL PRODUCTION OF ENTEROBACTER-AEROGENES IN CONTINUOUS CULTURE

The effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes from glucose was investigated in a microaerobic continuous culture. At a dilution rate of 0.20 h-1 and a fixed oxygen uptake rate (OUR) of 31.5 mmol l-1 h-1 the biomass concentration increased with pH ranging from 5.0 to 7.0, while the specific ATP requirement of the cells decreased. In the pH range 5.5-6.5 the product concentration (butanediol + acetoin) was maximal and nearly constant. However, the specific production continuously declined with increasing pH. Experiments with addition of acetic acid showed that the various effects of pH are due to inhibition of the by-product acetic acid on cell growth. The strength of the acetic and inhibition depended only on the concentration of its undissociated form [HAc]. The biomass concentration and the specific OUR were also only functions of [HAc], irrespective of the pH. Although the specific ATP requirement (qATP) strongly depended on the pH, [HAc] at constant pH. © 1990 Springer-Verlag.