Study On High Cell Density Culture Of Lactobacillus Helveticus IMAU60208

Lactobacillus helveticus IMAU60208 has good fermentation characteristics and great tolerance in gastric and intestinal juice. Milk fermented by this strain shows good effect of lowering blood pressure in vivo. The purpose of this study are to improve the viable counts of L. helveticus IMAU60208 through the optimization of culture medium and conditions and to provide theoretical guidance for developing microecologics with high viable counts and strong stability.The medium and static culture conditions of L. helveticus IMAU60208 were optimized and this work was based on the MRS medium. On this basis, the factors of high density culture were optimized and fermentation technology were determined by the comprehensive analysis of viable counts, optical density, cell dry weight percentage, alkali consumption and fermentation time of L.helveticus IMAU60208.The optimal medium of L. helveticus IMAU60208 was as follows:lactose 26.56 g, yeast peptone 68.12 g, anhydrous sodium acetate 4.45 g, K2HPO4 1.77 g, citrate sodium 1.42 g, MgSO4·7H2O 1.60 g, MnSO4·H2O 0.06 g, Tween-801.00 g, L-cysteine hydrochloride 0.05 g, β-carotene 0.02 g, orange juice 50 g, distilled water 950 mL. The optimal ststic culture conditions of L. helveticus IMAU60208 were as follows:fermentation temperature 37℃, nitial pH 5.5, inoculation amount 6%. Under this condition, the viable counts of L. helveticus IMAU60208 was 1.57×109 CFU/mL which was 6.60 times as many as in MRS medium (2.38×108CFU/mL).Through the further optimized the high density culture medium of L. helveticus IMAU60208, lactose concentration was increased to 60 g/L and other nutrient elements unchanged. Fermentation conditions as follows:fermentation temperature 37℃, initial pH 6.5, constant pH 5.9, inoculation amount 6%, nitrogen keeping pressure, revolution speed 150 rpm and neutralizing agent is 25% ammonia. To culture L. hehlveticus IMAU60208 based on these parameters, the high viable counts (5.08×109 CFU/mL) was obtained which was 2.24 times as many as before optimization (2.27×109 CFU/mL).