Preparation Of E-Polylysine With High Antibacterial Activity

Batch fermentation kinetics, quality analysis, classification and characterization of biological preservative ε-polylysine were studied in this article. The main research contents are as follows:Since s-polylysine was discovered, it’s production conditions have been continuously investigated and the production is also constantly upgrading. But most of them focused on the medium optimization and strain screening level. There have been no reports on the s-polylysine fermentation kinetics especially using it to improve the production. For that reasons, we have done the initial research. The substrate consumption, cell growth and product generation kinetic equation was initially established using the sigmoid model according to the changes of the substrate concentration, biomass, product concentration during the batch fermentation process. Parameters about the fermentation process was futher analysised, which provide a theoretical basis for the batch and fed-batch fermentation of s-polylysine.Now, s-polylysine has not yet been approved for use in China and their corresponding quality control indicators and methods have not been established. In light of that condition, We have discussed s-polylysine sample detection methods and quality analysis on the basis of s-polylysine criteria of Japan and South Korea. The quality of s-polylysine produced by Streptomyces albulus CGMCC1986was analyzed in this study. The chlorine content of the sample was determined by Volhard method, and the ratio of s-polylysine to s-polylysine hydrochloride was obtained. The content of s-polylysine in the sample was determined by both Kjeldahl and HPLC methods. The results showed that both of the two methods can be used to measure the content of s-polylysine in samples. However, the HPLC is a recommended method because of its simplicity and accuracy. Also the lead content was measured by atomic absorption spectrophotometry. In conclusion, these methods can be used to determine the quality of s-polylysine products, which provide some references on establishing the standard of s-polylysine.The functions of a given s-polylysine primarily depend upon its molecular size, s-polylysine with different MWs have different applications and s-polylysine produced by microbial method is a polydisperse polymer. If it can be fractionated, the different fractions can be used for different applications and the product’s quality can be enhanced, s-polylysine produced by Streptomyces albulus CGMCC1986was fractionated using ultrafiltration technique with2kDa and5kDa cut-offs of membrane. The number-average molecular weight of each fraction was determined by1H NMR method. The number-average molecular weights of the cut-offs of5kDa,2kDa and the filtrate are4230.95Da,3687.80Da and1900.82Da respectively.1H NMR indicates the chemical shifts of α-H, β-H, γ-H,δ-H and s-H are very similar to all the fractions. FT-IR spectra showed that the s-polylysine solid samples obtained by freeze-drying at pH=5with molecular weights higher than2kDa take on α β-turn conformation. However, the fraction with molecular weight smaller than2kDa adopts random coil structure. The antibacterial test proved that the fraction between2kDa and5kDa of membranes behaves the highest antibacterial activity than other fractions for the test strains of Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli and Shigella.