Screening Probiotic With High Capacity Of Producing Conjugated Linoleic Acid And Its Immunomodulatory Function

Cis-9, trans-11conjugated linoleic acid (c9, t11CLA) is octadecadienoic acid. C9,t11CLA has many biological effects, including immunomodulatory function. C9, t11CLA producing probiotic can converet dietary linoleic aicd (LA) to c9, t11CLA in theintestinal tract, and then enhance immunomodulatory function.In this study, the c9, t11CLA producing probiotic was screened, and subsequently the in vitro influencing factorof c9, t11CLA production and in vivo immunomodulatory function of the selectedstrains were investigated.One hundred ninety-three strains were selected from traditional Chinese fermentedfoods and feces. According to the ultraviolet colorimetry method,12strains werescreened for their ability to produce CLA. In particular, strains F0721, F0221, IN5.22,G14, M6and Q9were found with c9, t11CLA production ability by the gaschromatography (GC) detection. The six strains mentioned above were investigated forthe ability to survive in vitro simulating gastric juice, to grow in the presence of bile saltand to adhere to HT-29cell. The strain F0221was finally selected as c9, t11CLAproducing probiotic and was identified as Lactobacillus acidophilus F0221by16SrDNA gene sequence analysis. Incubation of L.acidophilus F0221at pH6.5followed byanaerobic incubation at37℃for40h was most effective (102.1±12.55μg/mL) inpromoting c9，t11CLA formation.The effects of Tween20, Tween40, Tween60and Tween80on L.acidophilus F0221growth and c9，t11CLA production in the ileum simulation liquid (ISL) with bile saltwere investigated in vitro. The results showed that the four kinds of Tween couldsignificantly (P<0.05) promote strain growth in the ISL. The reason was that theleakage induced by bile salt was reduced in the presence of Tween. Tween80couldsignificantly (P<0.05) promote c9，t11CLA production in the ISL, simultaneously. Oneof the reasons was attributed to the increase of production of LA isomerae of unit cell.Additionally, when the Tween80was added in the ISL, the18:1(c9) oleic acid, whichis the fat acid composition of Tween80, can enter the cellular and be converted into19:0(cyc) cyclpopropane fatty acid. These two fatty acids can inhibit the reduction ofcell membrane fluidity induced by bile salt.The effects of different prebiotics on L.acidophilus F0221growth and c9, t11CLAproduction were investigated in vitro colon simulation liquid (CSL). It was found thatgalactooligosaccharides (GOS) and arabinogalactan (AG) could significantly (P<0.05)enhance cell density and c9, t11CLA production of the strain.A major reason was thatthe metabolites of GOS and AG, including glucose and galactose, could promote the growth of L.acidophilus F0221in the CLS. Additionally, the metabolites of GOS andAG, including acetic acid, propionic acid and lactic acid, could increase cell membranepermeability, the chance of substrate LA into the cell, the contact frequency of LA andLA isomerase and then increase the c9, t11CLA production.The in vivo c9, t11CLA levels and immunomodulatory function of L.acidophilusF0221was investigated in mice. The results demonstrated that L.acidophilus F0221could significantly (P<0.05) increase lactobacillus count and c9, t11CLA levels in theileum and colon. This result indicated that the L.acidophilus F0221could grow andproduce c9, t11CLA in the intestinal tract. The levels of c9, t11CLA and oleic in serum,liver and adipose tissue were also significantly (P<0.05) increased, and the linoleic acid(LA) and arachidonic acid levels were significantly (P<0.05) decreased.At the sametime, the serum prostaglandin E2(PGE2) levels was significantly (P<0.05) decreased.Since the widely negative effects of PGE2in the immune system, the serum IL-2andTNF-α level, proliferation of spleen lymphocyte and phagocytosis activity of peritonealmacrophage were significantly (P<0.05) increased. These results indicated that theL.acidophilus F0221could enhance specific and non-specific immunity in mice.The effect of Tween80and GOS on functional properties of strain.F0221was alsoinvestigated in vivo. It was found that Tween80and GOS could significantly (P<0.05)enhance c9, t11CLA levels in vivo and immunomodulatory function in mice. Thesefinding suggested that Tween80and GOS might have potentiality as facilitating agentsthat help F0221to exert an enhanced immune function.