Studies Of Hawthorn Extracts Effects On Lactic Acid-Bacteria Growth-promoting And Its Growth Kinetics

Hawthorn is one kind of specialty fruit trees as medicinal and edible plants which originated in China 3,000 years.Pharmacology studies have shown that hawthorn maintain many functional and physiological activities.Many researches are focus on the flavone,phenolic compounds and triterpenic acid,but only few studies on proliferative effect of hawthorn polysaccharide on lactic acid bacteria.In this studies,extraction of hawthorn polysaccharide,proliferative effect of polysaccharide,and growth kinetics of lactic acid bacteria have been investgated.Water was used to extract the hawthorn polysaccharide in this study,and extraction condition was optimized through orthogonal experimental.The optimized condiction results are:solid-liquid ratio of 1:20,time of 6h,the temperature of 90?.Extraction rate of the precipitation polysaccharide is 3.92%with the condiction of one-tenth of the original volume,ethanol adding amount 5 times of extract of Hawthorn.The proliferative effect experiment shows that there are growth-promoting factors in hawthorn polysaccharides which have positive effect on L.B.and S.T.lactic acid bacteria.Optimizing Lactobacillus bulgaricus culture condition is 2%hawthorn polysaccharides,initial pH 6.5,and cultural temperature 42 ?.Optimizing Streptococcus thermophilus culture condition is 1%hawthorn polysaccharide,initial pH 6.5,temperature 42?.By comparing L.B.and S.T.lactic acid bacteria growth curve in the normal medium and optimized medium,it has been proved hawthorn polysaccharides' positive effect on the growth of L.B.and S.T.lactic acid bacteria.The maximum concentration of these two strains in optimized medium increase by 1.1 times and 1.2 times respectively when comparing with which in normal MRS medium.Using MATLAB software to optimize both Logistic equation and Luedeking-Piret-Like equation's parameter estimation and finish the nonlinear fitting.I dentified the growth kinetics model and substrate consumption kinetics model parameters,which the relative error is small and the global convergence is the least.The model expressed and equation's parameter are:Growth kinetic model of L.B.bacteria in the optimized medium:(?)Substrate consumption kinetic model of L.B.bacteria in the optimized medium:(?)Growth kinetic model of S.T.bacteria in the optimized medium:(?)Substrate consumption kinetic model of S.T.bacteria in the optimized medium:(?)Growth kinetic model of L.B.average deviation is 4.63%,root mean square error(RMSE)is 0.041,correlation coefficient is 0.997;Substrate growth kinetic model average deviation is 4.92%,RMSE is 0.881,correlation coefficient is 0.997.Growth kinetic model of S.T.average deviation is 2.30%,RMSE is 0.021,correlation coefficient is 0.998.Substrate growth kinetic model average deviation is 3.21%,RMSE is 0.726,correlation coefficient is 0.997.The analysis indicated that the growth kinetics model can be represent the growth kinetics characteristics of Lactobacillus bulgaricus and Streptococcus thermophilus in optimized medium.