Long chain dicarboxylic acid (DCA) produced by Candida tropicalis is produced in an aerobic viscous fermentation system. The gas-liquid transport resistance can be overcome and the oxygen supply can be increased by adding hydrogen peroxide (H_2O_2) to the fermentation system. This paper shows that H_2O_2 can not only enhance the oxygen supply but also change the metabolism by inducing cytochrome P450, the key enzyme of α, ω-oxidation. When C. tropicalis was cultivated in a 3-liter bioreactor using the combination of aeration and hydrogen peroxide feeding, the DCA yield increased about 10% except at the beginning of H_2O_2 feeding. The experiments showed that the maximum activities of P450 could be induced at 2 mmol·L -1 H_2O_2. By adding H_2O_2, the DCA yield in a 22-liter bioreactor was increased 25.3% to 153.9 g/L.
A method of reduced CO\|difference spectrum was established to study the cytochrome P450 activity of the whole cell of \%Candida tropicalis\% during the alkane converting process. Using this method, the cytochrome P450 activities of the whole cells that were cultured in the different concentrations of alkane were studied. The results showed that the 5% alkane could induce the cytochrome P450 activity obviously but not inhibit the growth of cells, so it was determined preliminarily that the alkane concentration of the seed medium was 5%. The cytochrome P450 activities of dicarboxylic acid (DCA) fermentation processing were further studied. During the exponential phase of growth, the cytochrome P450 activity increased smoothly. However, during the phase of production of dicarboxylic acid, the cytochrome P450 activities increased rapidly after a sort decrease. The results still showed that the rate of production of dicarboxylic acid increased with the cytochrome P450 activity.
