Effects and mechanisms of H 2 O 2 on production of dicarboxylic acid

The system of producing long chain dicarboxylic acid (DCA) by Candida tropicalis is an aerobic and viscous fermentation system. A method to overcome the gas‐liquid transport resistance and to increase oxygen supply is by adding hydrogen peroxide (H 2 O 2 ) to the fermentation system. Here we report that the H 2 O 2 not only can enhance the oxygen supply but also change the metabolism by inducing cytochrome P450, the key enzyme of a, o‐oxidation. When C. tropicalis was cultivated in a 3‐L bioreactor using the combination of aeration and H 2 O 2 feeding, DCA production rates increased by about 10% after a short period of decrease at the beginning. Furthermore, the experiments showed that the maximum activities of P450 could be induced at 2 mM H 2 O 2 , and the inducible mechanisms are also discussed. Moreover, we suggest that alkane might be oxidized through the “peroxide shunt pathway” when H 2 O 2 is present. By adding H 2 O 2 , the DCA yield in a 22‐L bioreactor could increase by 25.3% and reach 153.9 g/L. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 456–462, 2001.