Production of conjugated linoleic acids by Lactobacillus plantarum strains isolated from naturally fermented Chinese pickles

Naturally fermented pickles harbour many lactic acid bacteria(LAB).Forty-three LAB strains with conjugated linoleic acid(CLA)-producing ability were isolated from three naturally fermented pickle brines.Of these isolates,lp15 identified as Lactobacillus plantarum by API 50 CHL system and full-length 16S rDNA sequence analysis exhibited the highest CLA-producing ability(26.1% conversion) at 48 h in de Man Rogosa Sharpe(MRS) broth in the presence of 100 μg/ml of linoleic acid(LA).Compared to other strains,L.plantarum strain lp15 showed the highest tolerance upon increased levels of LA in the medium,i.e.,up to 600 μg/ml.This strain converted about 25% of LA into CLA isomers [predominantly cis-9,trans-11 CLA(9-CLA) and trans-10,cis-12 CLA(10-CLA)],of which 75% was 9-CLA.Interestingly,though the conversion rate of LA into CLA by lp15 remained stable between 100 to 600 μg/ml LA levels in the medium,it dropped sharply at 1000 μg/ml.Taken together,the lp15 strain displayed relatively high LA tolerance with higher conversion rate,which implies that this strain is a valuable candidate for enhancing the CLA content in food-sources like pickles.