Background: Many investigations have attributed bio-functional properties to a range of conjugated fatty acids (CFAs) of which the conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers have displayed potent health beneficial effects in a large number of in vitro and in vivo studies. CLNA isomers are naturally present in high concentrations in a variety of seed oils but relatively in small amount in meat and dairy products. However, some reports have shown the microbial production of such enzymes by lactic acid bacteria that convert linolenic acid (LNA) into CLNA. Present study aims to isolate CLNA producing lactobacilli of different origins and their potential to produce different CLNA isomers in MRS media.Methods: LNA containing MRS media was used for the isolation of lactobacilli and genotypic screening was done for the linoleate isomerase gene (LAI). Spectrophotometer was used to know the initial total fatty acid production and finally CLNA isomers were confirmed by the gas chromatography and their amounts were calculated. For this study, a total of 274 samples were collected from human milk, feces and dairy based fermented and non-fermented products, lab isolates and 178 lactobacilli strains were taken for CLNA screening. For conjugated isomers production by isolates, MRS broth with LNA at concentration of 0.5 mg/ml was used and incubated at 37°C for 48h. Results: Out of 178; only 40 isolates were able to survive at the tested LNA concentration. Finally, these 40 isolates were screened for conjugated double bond using spectrophotometer at 234nm. The highest conjugated fat producing isolates were further analyzed for c9, t11, c15 and t9, t11, c15 isomers using gas chromatography. Nine isolates in presence of LNA confirmed the production of CLNA isomers, C18:3 (c9, t11, c15 and t9, t11, c15). Only three isolates produced CLNA from LNA in MRS in a range of 52 to 80μg/ml and the rest 29 to 45μg/ml. Conclusion: Most likely, this is the first report describing CLNA production from lactobacilli isolated from human feces and fermented dairy products. Bioconversion of LNA into CLNA isomers opens newer options for the treatment of diseases. Therefore, it would be beneficial to get promising CLNA producing lactobacilli for improved absorbability and cure gastrointestinal disorders.
Keywords: Lactobacilli, conjugated fatty acid, conjugated linolenic acid, α-linolenic acid and conjugated linoleic acid, linoleate isomerase gene.