Identification and functional expression of a Δ9 fatty acid desaturase from the marine bacterium Pseudoalteromonas sp. MLY15

A gene putatively encoding a Δ9 desaturase-like protein was cloned from the isolated marine bacterium Pseudoalteromonas sp. MLY15. The 1134 bp open reading frame, designated as PhFAD9, codes for a 377 amino acid peptide with a molecular weight of 43.4 kDa. The protein was supposed to be a membrane-bound desaturase and its possible topology model was predicted using the Phobius program. The PhFAD9 protein was confirmed to be functional with high Δ9 desaturase activity when expressed in Escherichia coli. The PhFAD9 E. coli transformant accumulated palmitoleic acid, which accounted for 91.7% of the cellular C16 fatty acids after 2 h of induction. The ability for bioconversion of stearic acid to oleic acid was also demonstrated by supplementing the medium with exogenous stearic acid.