Repression of fatty-acyl-CoA oxidase-encoding gene expression is not necessarily a determinant of high-level production of dicarboxylic acids in industrial dicarboxylic-acid-producing Candida tropicalis.

The synthesis of dicarboxylic acids (DCAs) in Candida tropicalis is thought to be induced by a decrease in fatty acyl-CoA-oxidase activity. However, in the present study we demonstrate that repression of the POX4 gene, encoding fatty acyl-CoA oxidase, does not directly lead to high-level production of DCAs. No fatty acyl-CoA-oxidase activity was detected if the POX4 gene of C. tropicalis strain 1098 (wild-type strain) was disrupted. Furthermore, introduction of the POX4 gene from C. tropicalis strain M1210A3, which is a mutant derived from strain 1098 and is used as an industrial DCA-producing strain, still exhibited low-level fatty acyl-CoA-oxidase activity. Nevertheless, production of DCA was not observed in either case. Furthermore, the increase in acyl-CoA-oxidase activity by expression of the POX4 gene in strain M1210A3 did not reduce high-level production of DCA. These results suggest that alterations in acyl-CoA-oxidase activity are not necessarily related to production of DCA in industrial DCA-producing C. tropicalis M1210A3.