White Produced By Streptomyces Natural Preservatives Polylysine Research

ε-polylysine is a kind of biopreservative with better inhibitory capability and great commercial potencial.The microbe fermentation ofε-polylysine has been industrialized. But the fermentation technology ofε-polylysine is not mature in our country, the development and production are just at the first floor. So the study on production technology ofε-polylysine possess great values.In this project, we separate a new strain from the solid and it is identified as Streptomyces albulus 1-25 , and it is used as the test strain to ferment polylysine . We also study the culture and fermentation conditions and the characteristics of polylysine that we purified , and that is the basic job we do to the future work .The yeast extract and mealt power medium is the best solid medium of Streptomyces albulus 1-25 . We measure the growth curve of Streptomyces albulus 1-25 , then we find that 12~36h is the logarithm growth time , 36~60h is the stable time .Through the orthogonal experiment , we get the seed optimization medium: 5%starch,0.25% N peptone,0.004% ZnSO4·7H2O,0.05% MgSO4·7H2O,0.003% MnSO4,0.272% KH2PO4,0.716% Na2HPO4·12H2O;and the optimization medium: 5%glycerol,1.5%(NH4)2SO4,0.6% yeast power,0.004% ZnSO4·7H2O,0.05% MgSO4·7H2O,0.003% FeSO4 ,0.272% KH2PO4,0.716% Na2HPO4·12H2O。The inhibitory substance produced by S.albulus1-25 is identified as protein or polypeptide through special colour reaction , and determined as polylysine using amino acid analysis machine . The molecular weight of the polylysine is about 13,000 , and it is determined by the Tricine-glycerol-SDS-PAGE electrophoresis .Polylysine can be easily dissolved in the water; it possesses an extremely strong heat tolerance, which could be judged from the unconspicuous change of antimicrobial activity after placing at 120℃for 50min; it has effective inhibitory activity at wide pH range; it is not sensitive to the protease , only papain can effect its inhibitory activity partly .Polylysine has a broad antimicrobial spectrum, which can be judged from the study on the antimicrobial range. It displays a strong inhibitory activity against gram-positive bacteria including many pathogens and food spoilers, Bacillus megaterium, Listeria sp., Salmonella sp., Proteus vulgaris, Shigella sp., Bacillus cereus, Staphylococcus aureus, Micrococcus flavus, Bacillus subtilis, Lactobacillus plantarum, Streptomyces albulus, as well as gram-negative bacteria E.coli and yeast Saccharomyces cerevisiae.