Study On Microencapsulation Of Probiotics And Freeze-drying Protectant

With the development of science and technology,the application of antibiotics has become more and more extensive.Many adverse effects have happened because of the antibiotics abusing,such as drug resistance,destruction of the organism's microbial flora,antibiotics accumulation,etc.Probiotics have attracted more and more attention because of their ability to produce bacteriostatin,regulate the intestinal flora and enhance the body's immunity and its special safety and environmental friendliness.In theory,the intake of active lactic acid bacteria beverages can provide probiotics for the human intestines and promote intestinal health.However,it is necessary to ensure that lactic acid bacteria are colonized in the intestinal tract in a living state and in sufficient numbers in order to play a probiotic effect in the human body.The current probiotic products would reduce the activity of probiotics due to adverse environmental impacts in the process of production,processing,transportation and storage,which is also one of the main reasons why they cannot be widely used in industrial production.This article mainly took a strain of lactic acid bacteria screened in the laboratory as an example to study the microencapsulation and freeze-drying protective agent.The main research contents and results are as follows.Screening of strain and optimization of its culture conditions: 43 strains of lactic acid bacteria were screened from the shrimp intestines using MRS plates.Hemolysis and antibacterial experiments were performed on these lactic acid bacteria.The experimental results showed that none of the 43 strains had hemolytic activity.Among them,12 strains had better antibacterial activity against Vibrio parahaemolyticus,and RZ-6 had the highest antibacterial activity.After molecular biology and physiological and biochemical experiments,RZ-6 was identified as Lactobacillus pentosus.In this article,it was named L.pentosus RZ-6 and used in later experiments.The influence of temperature,p H,initial inoculum volume and liquid volume on the culture of L.pentosus RZ-6 was studied and the culture conditions of the bacteria were optimized by response surface analysis.The experimental results showed that the optimum culture temperature,initial inoculum and p H of the bacteria were 37.28°C,1.59% and 6.55,respectively.However,in order to facilitate the actual experimental operation,the culture condition combination was finally adjusted to: temperature 37±1°C,inoculation amount 1.5%,and initial p H of the medium 6.5.Research on embedding agent: the influence of the ratio of bacterial to gel,stirring speed,emulsifier dosage and the amount of glacial acetic acid on the embedding rate of probiotic were discussed.The experimental results showed that the entrapment rate of probiotics was the highest at the following conditions: the ratio of bacterial to gel was1:4,the stirring speed was 600 rpm,and the emulsifier dosage was 0.4 m L,the amount of glacial acetic acid was 0.6 m L.In order to further improve the long-term storage and transportation of probiotic microcapsules,it needs to be freeze-dried.However,the freeze-drying protective agent plays a key role in the preparation process of freeze-drying.In order to explore the function of sodium hyaluronate as a freeze-dried protective agent,this article discussed the effect of sodium hyaluronate,trehalose,skimmed milk and gelatin as a kind of lyophilized protective agent in single or mixed form on the embedding rate of probiotic microcapsules after lyophilization.The experimental results show that compared with a single component as a kind of freeze-dried protective agent,the above four components in a mixed form as a kind of freeze-dried protective agent had a higher embedding rate of the probiotic microcapsules after freeze-drying,and the optimal combination was :sodium hyaluronate 0.2%,gelatin 1%,trehalose 5%,skimmed milk 10%.After the test of acid resistance,enteric solubility and storage stability,it is found that the viable bacteria survival rate of the probiotic microcapsules after freeze-drying is the highest.As a kind of lyophilized protective agent,sodium hyaluronate has a greater protective effect on probiotics,and does not affect the acid resistance and enteric solubility of the microcapsules,and is beneficial to its in vitro storage.