Candida tropicalis can metabolize alkanes or fatty acids to produce long-chain dicarboxylic acids (DCAs). Fatty acid transporters located on the cell or peroxisome membrane may play an important role in this process. Using amino acid sequence homologous alignment, two putative proteins, CtFat1p and CtPxa1p, located on the cell and peroxisome membrane were found, respectively. Moreover, single- and double-knockout homologous recombination technology was used to study ctfat1p and ctpxa1p gene effects on DCA synthesis. In comparison to the wild-type strain, long-chain DCA yield decreased by 65.14%, 88.38% and 56.19% after single and double-copy knockout of ctfat1p genes and double-copy knockout of ctpxa1p genes, respectively, indicating that the knockout of ctfat1p and ctpxa1p genes had a significant effect on the conversion of oils and fats into long-chain DCAs by C. tropicalis. However, the yield of long-chain DCAs increased by 21.90% after single-knockout of the ctpxa1p gene, indicating that the single-knockout of the ctpxa1p gene may reduce fatty acid transport to peroxisome for further oxidation. Moreover, to improve the intracellular transport rate of fatty acids, ctfat1p copy number increased, increasing DCA yield by 30.10%. These results may provide useful information for enhancing the production of long-chain DCAs by C. tropicalis.
Keywords: Candida tropicalis 1798; Ctfat1p; Ctpxa1p; Fatty acid transporters; Long-chain dicarboxylic acids.