Microcapsule Of Streptococcus Lactic And Fermentation For Nisin

Nisin is a kind of active poly peptide substances with characteristics of high effectiveness, safety, nontoxicity, also known as nisin from streptococcus lactis, produced by fermentation of lactococcus lactis and it’s composed with 34 amino acids. As the only one allowed to commercial production of inartificial food antiseptic, nisin can inhabit the growth of most of the gram positive pathogenic bacteria, and it was widely used in dairy products, meat products, canned products, beverage and pharmaceutical fields.The way of microcapsulation microbial cells fermentation can enchance the concentration of fermentation products, yield and productivity, achieving cell reutilization and continuous fermentation, as a rusult, decreasing the cost of production, While simplifying product separation process, reduce the accumulation of product feedback inhibition of cell, aimed at increasing the unit titer and yield of nisin. The development and utilization of nisin can save energy, improve product quality, extend the storage time. Currently more than 50 countries and regions are allowed nisin as a food preservative, it has great commercial value.This paper focuses on the study of the preparation of Streptococcus lactis microencapsulated and fermentation process, explores factors that influence the activity of nisin, optimize cellular microcapsule preparation and fermentation conditions, and improve the titer unit and yield of the product. The main research contents and results were as follows:The MRS was used as the fermentation medium by Streptococcus thermophilus and determination of titer unit of nisin was done by agar diffusion method. Based on the results of single factor tests, the optimization fermentation conditions for producing Nisin were explored by response surface analysis methodology. The experiment results showed that the optimal fermentation conditions were p H 6.60, inoculation amount of 4.80% and corn steep liquor content of 25.00%, and corn steep liquor content is the key factor affecting the fermentation titer unit of Nisin. The second factor is the initial p H. The amount of inoculation is the minimal factor. Under these conditions, the Nisin titer unit reached up to 5102.77 IU/m L.First, sodium alginate and chitosan were used as raw materials to prepare ACA microcapsules, and the obtained microcapsules were coated by ethyl chitosan(CHI). Respectively microcapsule membrane expansion, embedding ratio, and titer unit of Nisin were determined and as the evaluation index. Study on various parameters affecting the preparation of ACA liquid core microencapsulation. The results show that: the degree of chitosan is 91% and the molecular weight was 74000; 15g/L sodium alginate and chitosan 5.0g/L, 20g/L Ca Cl2, 40mmol/L sodium citrate, curing time was 120 minutes, film forming time was 30 minutes, liquefaction time was 9 minutes, chitosan p H 5.5, sodium citrate soluble p H 5.0. Under such processing conditions, the rate of membrane of the prepared microcapsule expansion is 7.02%, the embedding rate is 86.24%, the titer unit of Nisin reached up to 5109.6 IU/m L.Affecting the performance of the ACA microcapsule of significant factors were Chitosan concentration, the p H of Chitosan solution and liquefaction time by the result of placket-burman experiment for single factor analysis, the level of main factors were decided when approaching maximum response area by the design of steepest ascent. Box-Behnken experimental design and response surface analysis to determine the best conditions on the performance of ACA microcapsules, the results were as follows: Chitosan concentration of 5.0 g/L, the p H of chitosan 5.5, liquefaction time was 12 minutes, the process conditions of preparation of microcapsule membrane expansion rate was 2.67%, the embedding rate was 91.79%, the titer unit of Nisin reached up to 5309.6 IU/m L. ACA microcapsules of SEM results showed that the space in the microcapsule capsule membrane had loss of space network structure, and exhibited good permeability.Study on microencapsulated Streptococcus lactis nisin fermentation, though compared with the free cell fermentation, the results showed that the microcapsule cell had much advantages than free cell fermentation,and the microcapsule cells have a longer fermentation period and higher titer unit of nisin, and can be used continuously about 12 batchs. Adsorption method was applied to separate the nisin of fermented liquid, the titer of Nisin was 44741.2IU/m L, Nisin was purified up to 8.44 times. Fermented liquid was analysed qualitatively by HPLC technique, the image showed that fermented liquid contained Nisin.