Study On The Biosyntyesis Of Exopolysaccharide Of Lactic Acid Bacteria In The KUMISS

Forty-one stains of the Lactic acid bacteria were isolated from the samples of Kumiss from the pastoral area in Xilin Guole. Numerous Lactic acid bacteria had been examined for their exopolysaccharides roduction capacities. The result clearly showed that the highest yield of exopolysaccharides produced by Lactobacillus.sake BXR-5-3. The effect of carbon source, nitrogen source, salts and optimum initial pH value of medium on exopolysaccharides produced by Lactobacillus. Sake BXR-5-3 were studied and a new culture medium (named as MRSB) for the biosynthesis of exopolysaccharide was formulated. The medium had following composition: peptone,1.5%; trypton,1.0%; glucose,1.5%; lactose,1.5%; K₂HPO₄,0.2%; MnSO₄·4H₂O, 0.02%; MgSO₄·7H₂O,0.02%; Sodium acetace,0.5%; yeast,0.5%; Tween80, 1 mL/L. The best culture conditions for Lactobacillus. Sake BXR-5-3 to biosynthesis EPS was that the constant pH was 6.0 of medium with fermentation at 35℃for 26h.Centrifugation, alcohol precipitatation and dialysis were applied to obtain the crude exopolysaccharides, which was further purified by column chromatography on DEAE-52 and sephadex G-200, and two exopolysaccharide fractions had been achieved. The exopolysaccharideâ… was examined by electrophoresis paper and sephadex G-200. The results indicated that the fraction was a homogenous substance. The average molecular weight of exopolysaccharide was 85100D by Sephadex G-200 gel chromatography. In addition, the exopolysaccharide could not inhibit the growth of Escherichia.coli,bacillus subtili,Staphylococcus and could not stimulate the growth of lactic acid bacteria.