Breeding Of ε-polylsine-producing Strain And Optimization Of Fermentation Process

The aim of our research was mainly focused on identifying the strain which was screened from soil by ourselves has the ability of syntheticε-polylysine,and then we establishment a method for sreening high-yield strains after mutation.Finally,we conducted a preliminary study on the process of Streptomyces albulus Z-18 fermentation.In this paper, LC -MS, NMR and Gel Permeation Chromatography (GPC) were used for studying the structure of theε-polylyine obtained by fermentation. The experimental results showed that theε-polylyine, with the average molecular weight of about 4210, is polymerized by mono-lysines with the aid of amide linkages betweenε-amino andα-carboxyl groups.The anti-bacteria activity experiment showed that theε-polylysine has very strong inhibitory effect on Bacillus subtilis.Strain operation is a very effective method for improving the strain production.As the Streptomyces albulus Z-18 metabolic pathway is also unclear,so traditional mutation is the only way to improve its capacity of producingε-polylysine. This paper used NTG effect on spores, withε-PL+Gly resistance as a screening plate.Through the establishment of this new type of mutation-screening method,we have got a mutantion strain which is production of 1.05 g/L,increased by 54% than Streptomyces albulus Z-18,and have a stability of genetics.At the end part of the paper, we studied the fermentation process parameters,inclucing dissolved oxygen, speed, ventilation and pH for determind which factor was the crucial for Streptomyces albulus Z-18 ferementation.The result of experiment showed that pH is the key factor during the fermentation.During the study of pH,we found that when Streptomyces albulus Z-18 was in above pH4.0,it is conducive to the growth of biomass,butε-PL is negative (about 0.8 g/L),and when the pH maintained at around 4.0,is conducive not only to the cell Growth,but also to theε-PL (above of 1.6 g/L).Subsequently,the fed-batch culture makes fermentation time extended to 98 h, and makes biomass reached about 20 g/L.At the same time,ε-polylysine production has also increased significantly. The highest output reached 8.02g/L, it is nearly 10 times than flask, and nearly 5times than batch fermentation.Thus,in the process of Streptomyces albulus Z-18 fermentation,controlling the conditions under pH4.0 and feeding carbon and nitrogen source could greatly improve the accumulation ofε–polylysine...