Study On Screening And Fermentation For Lactobacillus Producing Broad-specttum Lactobacillin

With the development of economic and society, the level of people's life is gradually increasing, thus people put forward higher request about food. At present, more synthetic preservative were added in most of the food, so existing potential safety problems, however lactohancillin is a natural preservative, and it catering to the need of all people.Lactohancillin is a kind of protein,polypeptide and preproghrelin, they come from the course of lactobacillus metabolism, they mainly used for inhibit-ing corruption bacteria and pathogenic bacteria during their reproduction and growth. At present, Nisin is widely used at home,it not only inhibits Gram-positie bacteria in food, and also can inhibits Gram-negative bacteria.Therefore,screening a new strain that can inhibit Gram-positie bacteria and Gram-negative bacteria is especially impor-tant.This paper take traditional fermented food from Anhui university farmers' markets as raw material, including acid fermented beans juice,cucumber juice,LaoZao juice,fermented bean curd,broad bean paste and pickles juice.First, enrich-ment training in skim milk medium, then I dilute enrichment broth by sterile water according to concentration gradient, coating,choosing the single colonies, scribing three times make it has been purified,and preservation.Purified strains were dyed by Gram stain, and lactic acid paper chromatography, screening Gram-positie strains, meanwhile preservation by cant. Finally,I take E.col,Bacillus subtilis,Staphylococcus aureus,Saccharomyces cerevisiae,Penicillium,Aspergillus niger for instructions bacteria.Using the oxford cup double agar diffusion method,detecting the diameter of bacteriostatic circle,after organic acids exclusion test and hydrogen peroxide alimina-tion test etc, I find a strain from cucumber juice, its antibacterial spectrum is wider, its bacteriostasis is also perfect, named it as H1 strain in this paper.In this paper, gram's staining,Sem photos,traditional physiological and biochemical tests,16SrDNA molecular identify and so on,All these methods confirme-d the strain,the strain is lactobacillus genera and Plants Lactobacillus(JDM1). Then I put H1 as original strains, researching fermentation in 500 mL triangle bottle, on this basis, based on 10 L mechanical agitation type fermentation tank, researching on fermentation dynamics.Mainly, measuring the bacteria content(dry weight method),glucose content(DNS method)and the size of bacteriostasis circle(the oxford cup double agar diffusion method)whth the changing time.Adopting Luedeking-Piret equation and Logistic equation to describe each index changes, fitting curve,in the end, I successfully build the dynamic mathematical models of mycelium growth,substrates consumption and product generation.Finally, I researched on the preparation of immobilized Lactobacillus plantaru-m by sodium alginate and fermentation. Results showed that the optimum technology conditions is 3.0% sodium alginate concentration,1.5% CaCl2 concentration and bacteria dilution ratio after centrifugation isl:5.Results of fermentation conditions of immobilized cell showed that the optimum pH of fermented filtrates is 7.0, the optimum temperature is 36℃, add 0.1% Tween80 to the medium, at this point, diameters of bacteriostatic circle is maximum, besides, NaCl concentration influenced the fermentation of immobilized cell greatly, So, NaCl concentration shuold be controlled strictly.Results of stability showed that the stability of immobilized cell have be improved greatly, the effect of continuous fermentation is good.