Short Chain Fatty Acid Biosynthesis in Microalgae sp. PCC 7942.

Short chain fatty acids (SCFAs) are valued as a functional material in cosmetics. Cyanobacteria can accumulate SCFAs under some conditions, the related mechanism is unclear. Two potential genes Synpcc7942_0537 () and Synpcc7942_1455 () in sp. PCC 7942 have homology with and encoding β-ketoacyl ACP synthases (I/II/III) in plants. Therefore, effects of culture time and cerulenin on SCFAs accumulation, expression levels and functions of these two potential genes were studied. The results showed sp. PCC 7942 accumulated high SCFAs (C12 + C14) in early growth stage (day 4) and at 7.5g/L cerulenin concentration, reaching to 2.44% and 2.84% of the total fatty acids respectively, where expression was down-regulated. Fatty acid composition analysis showed C14 increased by 65.19% and 130% respectively, when and were antisense expressed. C14 increased by 10.79% () and 6.47% () under mutation conditions, while C8 increased by six times in mutant strain. These results suggested is involved in fatty acid elongation (C <18) and the elongation of -16:1 to -18:1 fatty acid in sp. PCC 7942, while was involved in elongation of fatty acid synthesis, which were further confirmed in complementary experiments of . The research could provide the scientific basis for the breeding of SCFA-rich microalgae species.