Abstract: In this study, the ability of whole and disrupted cells of Lactobacillus plantarum p-8 and recombinant linoleate isomerase family from this strain to convert linoleic acid (LA) to conjugated linoleic acid (CLA) were evaluated and the underlying mechanism was explored. The results showed that whole and disrupted cells of L. plantarum p-8 cultured in MRS medium could inefficiently catalyze the conversion of LA to c9,t11-CLA, t10,c12-CLA and t9,t11-CLA, and only a small amount of t10,c12-CLA was observed in the cells. The results of real-time PCR exhibited that lower expression levels of linoleate isomerase family may be responsible for lower CLA production. Members of the independently expressed recombinant linoleate isomerase family, flavin denine dinucleotide (FAD) and nicotinamide adenine dinucleotide were found essential for the conversion of LA to c9,t11-CLA, t10,c12-CLA and t9,t11-CLA through a pathway consistent with that in L. plantarum AUK1009. Homologous modeling of linoleic acid hydrase presented three domains. The substrate-binding site and the FAD site were located in the hydrophobic cavity at the junction of the three domains. M76 and Y180 were essential residues.

Key words: fatty acid hydratase; hydroxyfatty acid dehydrogenase; acetoacetate decarboxylase; gas chromatography; homologous modeling