Study On Protection Reagents And Technics Of Active Microbial Agents Of LAB

The present thesis mainly focuses on the Lactobacillus acidophilus(LA) and Streptococcus thermophilus(ST).We investigated the technological conditions of bacterial powder using the vacuum freeze-drying technology and the active microbial agents preparation.Furthermore,we stressed to study the protective agents that add in the different technological processes.We have investigated the rules of the growth,propagation and metabolism for two strains. It's the foundation of producing the active microbial agents.With time on incubation for abscissae,with relevant pH value,acidity,bacteria count's logarithm for ordinate,mensurated the growth curves.Then we synthetically analyzed the growth curves and determined the optimum harvest date of the LA is 12～16 h under 5%inoculation and 37℃,well the optimum harvest date is 16～20 h under 5%inoculation and 42℃.The pH value of the incubation medium was adjusted to 5.6,5.8 and 6.0 with aseptic lactic acid solution respectively,and incubated under different temperatures.The results were that LA was incubated under the conditions of pH-5.8 and 37℃,as well as the optimum incubate conditions of ST was pH-5.6 and 42℃.We also chosed four natural and cheap additives as the growth promoting factors of two strains to study.The results suggest that all the four additives can promote the growth: tomato juice 5%＞tomato juice 3%＞carrot juice 5%＞beer 5%＞contrast(LA);beer 5%＞tomato juice 5%＞tomato juice 3%＞carrot juice 5%＞contrast(ST).On the basis of the above results,we studied the technology for the vacuum freeze-drying of two strains,we used improved TJA solid medium,double flat band method proceed viable count;centrifugation conditions selected 7000 rad/min,10min;Selected freeze-drying protectant was skimmed milk powder 10%+lactose 6%.We assayed the bacteria power:They were gram positive under microscope and without infectious microbe;water ratio≤3%;the live bacteria survival rate of LA was 69.33%,ST was 73.59%.We studied the active microbial agents of technology about the LA and ST.In order to improve the survival rate and prolong the validity of live bacteria in the two strains tablets,we optimized the protective agents for the two strains in the different technological processes.First we screened out the important factors about influenceing that the live bacteria survival rate by the Plackett-Burman Design when we were cultivating the Lactobacillus acidophilus and tablet forming.Furthermore,we obtained the regression equation of the important factors using uniform design,DPS experimental design and data statistical analysis software and determined the optimal level of the factors from the equatiion's extremum.So the four groups formula of protective agents was obtained,and they are LA expanding incubation protective agent (sodium chloride 0.3%,mannitol 0.4%,maltose 3.5%,Maximal livability y_1max=93.1695),LA tabletting protective agent(ascorbic acid 1.0%,sucrose 37.0%,y2_max=97.0612),ST expanding incubation protective agent(sucrose 0.5%,soluble starch 3.5%,y1'_max=94.5862) and ST tabletting protective agent(polyvinylpyrrolidone 12.0%,soluble starch 25.0%,sodium thiohsulfate 4.5%,maltose 2.5%,y2'_max=97.8468),respectively.Validated the four groups formula of protective agents's tablets,the results proved that they increased the live bacteria survival rate virtually.The finished products of active microbial agents were tested.We finded that the products have some properties,for example appearance complete,appropriate hardness,weight variation standard of pharmacopoeia,water ratio≤5%,and the living bacteria number of bacteria tablets in all the four groups greater than 2.5×10¹⁰/g.In order to investigate the periods of validity,we carried out the accelerated tests for the four groups of the bacterial tablets:three months after the tablets's live bacteria survival rate still≥10%,equivalent to at room temperature storaged 1 year.