Breeding And Fermentatlon Resarch On ?-PL Producing Bacteria

?-PL is a L-lysine homopolymer connected with a-carboxyl groups and e-amino produced by Streptomyces albulus or Kitasatospora sp. strains. The degree of this polymerization is 25-35 in general, and it is widly used in food and medical fields on account of its cationic property. This resarch mainly facus on strain mutagenesis, fermentation, separation and purification, and the study on antimicrobial properties.We got a strain named Streptomyces sp. DES20 through Gly mutagenesis, AEC mutagenesis, ultraviolet mutagenesis and diethyl sulfate mutagenesis with a production capacity of 0.368 g/L which is 87.76% higher than the original strain, this strain could grew well on seven different kinds of medium suitable for the growth of actinomycetes. Response surface design let us know the main factors druing the fermentation. On the basis of this we established a mathematical equation between ?-PL, glucose (A), ammonium sulfate (B) and yeast extract (C). We optimized the culture medium through response surface resign results and got a production of 0.41 g/L. The accumulation of ?-PL with batch fermentation is 2.637 g/L in a 5 L fermenter. In order to solve the problem of the lack of carbon source, we carried out fed-batch fermentation with a production of 6.701 g/L. Adding 2 g/L sodium citrate could either promote the bacterial growth or improve the ?-PL synthesis rate, ?-PL concentration was 8.351 g/L at the end of fermentation. The separation and extraction of ?-PL from fermentation liquid was using weak acid anion-exchange resin with two elution methods, using hydrochloric acid elution the recovery rate was 89.23%, and the purity of ?-PL was 95.12%, while the recovery rate and purity was 80.99% and 81.68% through ammonia elution. MALDI-TOF-MS showed the degree of PL1 is 26-33. UV, IR,1H-NMR,13C-NMR and HMBC proved our poly-L-lysine is ?-PL but not ?-PL. And it has obvious antimicrobial activities to several bacteria.