Studies On Screening Lactobacillus For Radix Astragalus Fermentation And Optimization Fermentation Parameters

Microbial ecological agents—probiotics, prebiotics and their combination"synbiotics"—would be increasingly used in stock raising, Thereinto, the important source of probiotics and prebiotics were lactobacillus and plant polysaccharides respectively. However traditional synbiotics were always simple combination of lactobacillus and plant polysaccharides, thus could not plays the potential of microbial fermentation, Studies indicated that fermented TCM had many advantages, such as improving the content of active components in TCM, enhancing efficacy and reducing toxic and side effects of TCM. So the study of TCM fermentation by lactobacillus in order to develop new synbiotics had significance. In this paper one fine lactobacillus with high fermenting performance for Radix Astragalus(RA )was obtained through acclimated mixed strains, besides, fermentation parameters of the fine strain were optimized in order to pave the way for developing new synbiotics food additive. The main conclusions as follows:1, Screening fine strain was made , one fine lactobacillus which could greatly improve the contents of crude polysaccharide of fermentation liquid was obtained and was tentatively identified as Lactobacillus: firstly, mixed strains were acclimated by repeatedly passed into fermentation medium which adding RA extract, secondly, 8 strains were selected by selective medium, thirdly, through studying on the influence of crude polysaccharide(CP)yield of fermentation liquid by these strains and the proliferation of these strains by RA extract, one fine strain , named FGM1, was successfully screened, which could make the CP yield of fermentation liquid improving 131%—from 5.64% of RA extract to 13.03%, meanwhile the proliferative of fine strain by RA extract was obviously and germ concentration increased by 110% compared to the blank control(The contents of crude polysaccharide were determined by anthranone-sulfuric acid colorimetric method and the germ concentration was measured by turbidimetry respectively).Finally, the fine strain was tentatively identified as Lactobacillus via morphologic studying and micro-biochemical identification,2, Optimization Fermentation parameters(Fermentation medium and Fermentation conditions)of the fine strain was carried out, the result indicated that Uniform Design and Artificial Intelligence are fast and efficient methods in fermentation parameters optimization: firstly the CP yield of fermentation liquid was regarded as optimization target, uniform design (UD) was used for the trial design of the formula of medium components, artificial neural network (ANN) was applied for the predicted model of the relationship between the CP yield and the concentration of medium components, the genetic algorithm (GA) was used for the global optimization of the fermentation medium and the optimized culture medium was proposed as follow: corn flour 42.10g/L, nitrogen source 7.45g/L, carrot powder 9.80g/L, KH2PO4-K2HPO4 1.80g/L and beef extract 6.25g/L.With the optimized culture medium, CP yield was 25.6%, which higher 6.85% than the original medium and the relative error between predicted value(24.81%) and experimental value(25.6%) was less than 4%, which fully meet the qualification in fermentation field. On the ground of getting the optimal medium, the CP yield of fermentation liquid was regarded as optimization target again, UD and optimization toolbox of MATLAB 7.1 were used to optimize fermentation conditions, including fermentation medium initial pH, fermentation time, fermentation temperature and inoculation quantity. Finally The optimal fermentation conditions was proposed as follow: fermentation medium initial pH 7.2, fermentation time 68h, fermentation temperature 38℃,inoculation quantity 5% and with the optimal fermentation medium and conditions, the CP yield was improved to 27.93% , increasing by 9.14% compared to before optimization and the relative error between predicted value(29.34%) and experimental value(27.93%) was less than 6% which approximately meet the qualification in fermentation field.