Abstract: Acyl carrier protein (ACP) is a key protein in fatty acid biosynthesis pathway of microorganisms. In order to promote the accumulation of fatty acids in Synechocystis, the homologous recombinant plasmid ssl2084⁽⁺⁾ was successfully constructed for overexpressing the ACP (ssl2084) gene and transformed into wild-type Synechocystis sp. PCC6803. Identification of the ssl2084⁽⁺⁾ mutant strain at the DNA and protein levels showed that the ssl2084 gene had been overexpressed. The content and composition of the fatty acids in the mutant strain under different temperatures were detected by liquid chromatography-mass spectrometry (GC-MS). The results showed that the contents of C12:0, C16:0 and C18:0 in ssl2084⁽⁺⁾ mutant at 30 ℃ were 1.50, 8.74 and 0.60 mg·g^-1, respectively, which increased by 54.71%, 50.82% and 155.86%, respectively, compared with the wild type. Under the condition of low temperature stress culture at 20 ℃, the contents of C12:0, C16:0 and C18:0 reached 1.70, 11.85 and 2.31 mg·g^-1, respectively, which increased by 31.94%, 47.35% and 39.90%, respectively, compared with the wild type. The above results indicated that overexpression of ssl2084 gene in Synechocystis sp. PCC6803 could increase the content of medium and long chain fatty acids, and the low temperature condition could further increase the content of medium and long chain fatty acids.

Key words: Synechocystis sp. PCC6803, acyl carrier protein, homologous recombination, medium and long chain fatty acid