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Characteristic Assay Of Two Lactic Acid Bacteria And Preparation Of Microcapsule Embedding Bacteria

Posted on:2022-05-27Degree:MasterType:Thesis
Country:ChinaCandidate:B J WangFull Text:PDF
GTID:2480306314450354Subject:Food Engineering
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Lactic acid bacteria are Gram-positive bacteria that can use fermentable carbohydrates to produce lactic acid.They can help regulate the balance of human intestinal flora and maintain intestinal homeostasis,which is of great significance for promoting human health.However,the prerequisite for the function of probiotics and health care is to have a sufficient number of viable bacteria.During the application of lactic acid bacteria,problems occur as the poor tolerance to the human body's acidic conditions and bile salts,and the interference of various adverse factors,which are not conducive for survival.As a result,the number of viable lactic acid bacteria decreases,and the probiotic effect of lactic acid bacteria cannot be played well.The use of microencapsulation technology to embed lactic acid bacteria can effectively protect the bacteria to resist the adverse environment and increase the number of viable bacteria,so that its probiotic effect can be better played.Two strains,including Lactobacillus bifidobacterium BMBL 0624 and Lactobacillius casei KJ 598784 in this study,were selected to do such experiments as antibacteria in vitro,antibiotic resistance,surface properties determination,tolerance and heavy metal adsorption.Their probiotic properties were investigated respectively.Subsequently,chitosan and pectin were used as the embedding wall material,microcapsules were prepared by the orifice coagulation bath method,the preparation process was optimized,the quality of the lactic acid bacteria microcapsules was evaluated,and the protective effect of the lactic acid bacteria was studied.The results were as follows.(1)Both Lactobacillus species inhibited Staphylococcus aureus,and L.casei fermentation broth inhibited Escherichia coli.B.lactis showed resistance to gentamicin and streptomycin,and L.casei showed resistance to streptomycin.B.lactis was more tolerant to low p H environment than L.casei,and better tolerated at p H 3.5.Within 24 h of incubation,B.lactis was able to grow and multiply under 8%high osmotic pressure,and the osmotic pressure resistance of B.lactis was better than that of L.casei.The heat tolerance of both lactic acid bacteria was better when treated at65?.The adsorption rate of heavy metal chromium ions by B.lactis and L.casei reached the maximum of 56%at 12 h and 24 h,respectively.Both lactobacilli showed some hydrophobicity,self-agglomeration and copolymerization.(2)A single-factor test was used to optimize the preparation process of lactic acid bacteria microcapsules.The main factors affecting the preparation of lactic acid bacteria microcapsules were chitosan concentration,pectin concentration,stirring speed,calcium chloride concentration,and bacterial gel ratio.The optimal conditions for the preparation of Lactobacillus microcapsules were determined using the encapsulation yield as the index.The results showed that the optimal conditions for the preparation of B.lactis microcapsules were 5%pectin concentration,1.5%chitosan concentration,3%calcium chloride concentration,180 r/min stirring speed,1:8 volume ratio of bacterial suspension to pectin,and 83.67%encapsulation yield.The optimal preparation conditions for L.casei microcapsules were:pectin concentration 6%,chitosan concentration 1%,calcium chloride concentration 4%,stirring speed 240 r/min,bacterial suspension and pectin volume ratio 1:8,and the embedding yield was 79.25%.(3)The moisture content of the prepared microcapsules was less than 20%,FTIR characterization shows that the hydrogen bond formed between the wall materials is the main binding force of the microcapsules.And the viable bacteria count could be maintained above 10~6CFU/g after simulated gastric juice treatment,and the viable bacteria count decreased by 3.5 orders of magnitude after simulated bile salt treatment.In simulated intestinal treatment,the two lactic acid bacteria microcapsules were released more completely after 150 min,and the microcapsules had better intestinal solubility and better ability of fixed-point release.The continuous simulated treatment can still maintain a certain number of viable bacteria,and the bacteria still have stability when stored at 4?for 30 days.In summary,this paper takes two lactic acid bacteria as the research object,and the growth characteristics of the strains were clearly examined by evaluating the characteristics of lactic acid bacteria,and prepareing lactic acid bacteria microcapsules with chitosan and pectin as the wall material by sharp pore coagulation bath method,which has certain protective effect on lactic acid bacteria.The product quality is well evaluated and basically achieves the expected effect.It provides a certain theoretical basis for increasing the types of microcapsules and developing and studying lactic acid bacteria with probiotic potentials.
Keywords/Search Tags:Lactic acid bacteria, Chitosan, Pectin, Microcapsules
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