Research On Coculture Of Lactobacillus Acidophilus And Lactobacillus Plantarum To Produce Conjugated Linoleic Acid

Conjugated linoleic acid (CLA), a mixture of positional and geometric isomers of octadecadienoic acids (C18:2) with conjugated double bonds, is natural fatty acid, which has many important physiological activities, such as anticarcinogenic, antiatherosclerotic, loss weight, antioxidative, antidiabetogenic and immunomodulative. At present, CLA is mainly synthesized by isomerization in industrial production, but the isomer is relatively complex. By biosynthesis of CLA, the isomer is unitary, the reaction conditions are mild and its primary product has biological activity c9,t11-CLA and the10t,12c-CLA isomer. Therefore, biosynthesis has been paid more and more attention.In this study, a strain selected from the clean rice water which can synthesize CLA, through the analysis of physiological and biochemical characteristics of microorganisms, was determined as Lactobacillus plantarum Y8, then Y8and Lactobacillus acidophilus kept in our laboratory were operated for optimal conditions of coculture fermentation. Ultraviolet spectrophotometry was used to analyze the content of CLA. To increase the content of CLA, Ultraviolet light and DES were used to create CLA-hyperbiosynthesis mutant. The fermentation conditions with CLA-producting strain were also optimized by Response Surface Design method.The fermentation conditions optimized on original Lactobacillus plantarum (Y8) and Lactobacillus acidophilus(La) in different media were summarized as follows:in SKM media-incubation temperature34℃, incubation time72h, inoculum size5%, initial pH5.5, substrate concentration4.0%, proportion of Y8and La was4:1, the concentration of CLA reached the maximum biosynthesis160.35μg/mL. In MRS media, incubation temperature34℃incubation time48h, inoculum size3.0%, initial pH6.5, substrate concentration3.5%, proportion of Y8and La was4:1, the concentration of CLA reached the maximum biosynthesis93.32μg/mLIt was proved that Ultraviolet mutagenesis and DES to induce Lactobacillus plantarum and Lactobacillus acidophilus produced two mutants with higher ability to transform LA to CLA than those of original strains. The screened two mutants Y8-1and La-1formed the maximum CLA with83.52μg/mL and65.371μg/mL respectively, whereas the original strains only produced CLA of43.61%for Y8-1or83.16%for La-1.The fermentation conditions were optimized on Y8-1and La-1by Response Surface Design method. The optimal conditions were that:culture temperature36.5℃,substrate concentration5.0%, initial pH6.5, inoculum size5%, incubation time48h, proportion of Y8-1and La-14:1, the concentration of CLA reached the maximum biosynthesis319.26μg/mL The CLA production increased more than99.1%of the original strain.