Effects and mechanisms of H2O2 on production of dicarboxylic acid

The system of producing long chain dicarboxylic acid (DCA) by Candida tropi calis is an aerobic and viscous fermentation system. A method to overcome t he gas-liquid transport resistance and to increase oxygen supply is by addi ng hydrogen peroxide (H2O2) to the fermentation system. Here we report that the H2O2 not only can enhance the oxygen supply but also change the metabo lism 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 aer ation and H2O2 feeding, DCA production rates increased by about 10% after a short period of decrease at the beginning. Furthermore, the experiments sh owed that the maximum activities of P450 could be induced at 2 mM H2O2, and the inducible mechanisms are also discussed. Moreover, we suggest that alk ane might be oxidized through the "peroxide shunt pathway" when H2O2 is pre sent. By adding H2O2, the DCA yield in a 22-L bioreactor could increase by 25.3% and reach 153.9 g/L. (C) 2001 John Wiley & Sons, Inc.