ACETIC-ACID - FRIEND OR FOE IN ANAEROBIC BATCH CONVERSION OF GLUCOSE TO ETHANOL BY SACCHAROMYCES-CEREVISIAE

yThe permissible region of growth of Saccharomyces cerevisiae on gluco se under anaerobic conditions was determined as a function of both pH and the concentration of added acetic acid to the medium. In the absen ce of acetic acid, growth was possible at a pH as low as 2.5, whereas a total acetic acid addition of 10 gl(-1) increased the minimum allowa ble pH for growth to 4.5. The results showed that the concentration of the undissociated form of acetic acid should not exceed 5 gl(-1) in t he medium for growth to occur. The addition of acetic acid had a profo und effect on growth energetics, thereby leading to an increased ethan ol yield on glucose. At a concentration of 3.3 gl(-1) of undissociated acetic acid, the ethanol yield was 20% higher than without added acet ic acid. Furthermore, the biomass and glycerol yields decreased by 45 and 33%, respectively. (C) 1997 Elsevier Science Ltd.