Screening Bacteria Producing ε-PL And Activity Research

Poly-ε-lysine (ε-PL) is an unusual cationic, naturally occurring homopolyamide made of L-lysine, having amide linkage between ε-amino and a-carboxyl groups. ε-PL can inhibit the growth of gram-positive bacteria and gram-negative bacteria, and even can inhibit the growth of pathogens. Because ε-PL is water soluble, biodegradable, edible and nontoxic toward humans and the environment, it is an ideal biological preservatives.This topic mainly study the strain screening, purification and characterization of ε-PL, identification species and conformation of ε-PL.At last, we also increased the production of ε-PL.Prouducing ε-PL strains is from the collected soil, which is from Beijing, Taian, Langfang, Xuanhua, Xi’an, Hangzhou, Nanjing, Kunming and other places. s-PL could be visualized as a distinct colony on the agar plate by detecting the interaction between basic charged groups of secreted ε-PL with acidic dyes. ε-PL was isolated and purified from the culture broth by ion exchange chromatography on an Amberlite IRC-50(H+form) column at pH8.5. By extracting the16SrDNA and observe colony morphology under microscope, the strain is Streptomyces albulus. Strain-24has antiphage activities to gram-positive bacteria and gram-negative bacteria. Finally determation the production of ε-PL by using ultraviolet spectrophotometer, the production of ε-PL is0.19g·L-1Using strains-24as starting strain, mutant strain with combined UV and diethyl sulfate (DES) was inoculated into plate,which is with glycin and ε-PL medium for screening high producing strain. A high ε-PL producing strain was obtained after optimization of concentration of glycin and ε-PL, dosage of UV and diethyl sulfate (DES) and secondary screening. Production of ε-PL reached0.39g·L-1, which was increased105%of starting strain.We increase ε-PL production through optimization of the culture medium. Glycerol,(NH4)2SO4are important in the fermentation. The optimal concentration of the factors was further investigated.At present, many studies of Streptomyces fermentation used M3G medium which glucose as carbon source, yeast extract as organic nitrogen source, ammonium sulfate as inorganic nitrogen source.We improved the M3G medium to increase the productive,which make production of ε-PL reached0.41g·L-1.