Studies On Synthesis And Enhanced Immunity Of Exopolysaccharides Of Lactic Acid Bacteria

This study aimed at selecting the strain,choosing the culture medium and optimizing thefermented conditions to the highest yield of EPS produced by lactic acid bacteria,andenhancing immunologic functions by LAB EPS.In addition,EPS was produced by whey.Twenty stains of Lactic acid bacteria were isolated from fermented productions.Numerous Lactic acid bacteria had been examined for exopolysaccharides productioncapacities.The result clearly showed that the highest yield exopolysaccharides production byLactobacillus plantarum.By comparing the yield of EPS, the Eiller culture medium was choosed from MRS、ATP、SL and Eiller.Then，the effect of carbon source, nitrogen source, salt and the optimuminitial pH value of medium on EPS produced by Lactobacillus plantarum were studied. Anew culture medium (named as E1) for the synthesis of exopolysaccharides by Lactobacillusplantarum was formulated.The suitability of the semi-defined culture medium was obtained,the medium had following compositions: peptone13.3g,sucrose13.3g,glucose13.3g,yeastjuice5.0g,NaCl4.0g,gelatin2.5g, CH3COONa1.5g,Vitamin C, deionized water1000mL.The optimum fermented conditions were determined by L9（34）orthogonal experiments.The optimum fermented conditions were pH5.2at cultures with45℃for22h.The EPSconcentration was881.90mg/L.The exopolysaccharides were further purified by column chromatography on DEAE-52and sephadex G-100, and two exopolysaccharide fractions had been achieved. The averagemolecular weight of exopolysaccharide Ⅰ was1.5×10~5and exopolysaccharide Ⅱ was1.1×10~4.Exopolysaccharides produced by Lactobacillus plantarum was one kind of naturalnontoxic products.The exopolysaccharides had many biological functions.To study thefunctions of the exopolysaccharides,this studies examined the effects of theexopolysaccharides on the physiogical function of the mice. Comparid with NS group,all theEPS groups had enhanced the phagocytic index of mouse apoposis and the weight of themouse spleen and thymus gland apparat(P<0.05or P<0.01).The crude EPS(high dosage) had enhanced the the delayed type hypersensitivit(P<0.05or P<0.01).The purity EPS(high dosage)and crude EPS(low,high dosage) had diminished hemolysin production(P<0.05or P<0.01).The purity EPS(high dosage) and crude EPS(high dosage) had enhanced lymphocytetransformation capacity(P<0.01).The results showed:the EPS can enhanced the immunologicfunctions of mice.