Studies On High-density Cultivation And Freeze-drying And Technology Of Lactobacillus Reuteri LT018

Lactobacillus reuteri LT018 is a probiotic strain derived from the centenarians in Bama.The LT018 clear origin and distinct characteristics has a variety of potentially probiotic functions which has a strong tolerance to simulated gastrointestinal fluid,adhesion propagation and antibacterial capacity.In order to investigate its value,and provide the high-quatity materials for developing the safe and high quality efficient lactic acid bacteria fermentation agent and probiotic products.The sdudy was made from the following aspects:1.In order to achieve its high cell-density growth,in this study,on the basis of TPY fermentation,a certain fermentation components of the LT018 was developed through the single factor method which can be illustrated as follows:tryptone,yeast powder,malt sugar,citric acid,sodium citrate,tomato juice and L-cysteine.The Plackett-Burman experiment was used to find that tryptone,citric acid and L-cysteine have significant impact on the probiotics’ growth.Then the steepest ascent experiment was designed to approach fast the optimum area,and the response surface analysis was used to optimize the combination of significant factor,and the optimum condition was that tryptone content was 12.13 g/L,citric acid content was 0.4 g/L,L-cysteine content was 0.6 g/L.Under this condition,the culture conditions was determined as follow:4%of I nocula,37℃,initial pH 6.7 and statically cultured.The result showed that the viable count of LT018 was 7.13×1010cfu/mL,which was 10.7 times compared with the count before optimization.Through this study,the medium was optimized,and the final viable count and the optimized multiple were significantly improved compared with the related reports.2.Based on skim milk as a protective agent,the vacuum freeze-drying study was conducted using the Lactobacillus reuteri LT018.As far the saccharides,amino acids,alcohols the single factor expriment was conducted the response surface design was used for optimizing the compound protective agent.In the single factor experiment,the antifreeze factors were obtained as follows:sucrose,glycerol,glycine.Then the response surface method was used to optimize the lyophilized protective agent of the Lactobacillus reuteri.The optimal ratio of the lyophilized protective agent 10.00%of skim milk powder,5.73%of sucrose,and 2.97%of glycerol and 0.69%of glycine,the 80.98%of cell viability was obtained after lyophilization.Compared with the related reports,this study reduced the cost of protectants and increased the survival rate of lyophilized cells.3.The Lactobacillus reuteri LT018 powder was used to conduct the simulated gastrointestinal tolerance test,and the viable count was determined.The results showed that the survival rate of the Lactobacillus reuteri LT018 powder was 97.67%after simulated gastric fluid treatment and 89.79%after the simulated intestinal fluid treatment.Therefor Lactobacillus reuteri LT018 powder has a strong gastrointestinal tolerance.There are few reports on the Lactobacillus reuteri,but the Lactobacillus reuteri powder has a stronger gastrointestinal tolerance than other the Lactobacillus.Lactobacillus reuteri LTO18 powder has the feasibility of development.4.The stability of the Lactobacillus reuteri LT018 powder was investigated.The results shoeed that the stability was the best at-20℃,and the survival rate was the highest.Three months after the survival rate of was 57.0%after three months.