Screening And Identification Of High ε-Poly-L-lysine Producing Strains And The Fermentation Research

ε-Poly-L-lysine is a kind of natural microbial food preservative, it has excellentanti-corrosion properties and commercial potential in the domestic food industry. It ownsgreat prospects for development. In Japan, ε-Poly-L-lysine has achieved output of thousandsof tons of industrial production annually, but in the domestic the technology is still part of thelaboratory and exploratory stage, the development and industrialization of ε-pL productionhas been the blank. Therefore, the research of the industrial production of ε-pL has a veryimportant significance. The main research done as follows：（1） In this essay, we filtered out three higher yield of ε-pL producing bacterias throughthe filter medium and some natures of the qualitative and quantitative detection from the soil.Then, the three identified strains were done through physiological and biochemical and16SrDNA sequencing methods to determine the three bacteria species. Next, the highest yieldstrain of the three bacterias was mutageniced by NTG and screened out by resistant plate.Finally, the ε-pL production mutanted and increased strain was finally obtained.（2） Through physiological and biochemical and the16S rDNA sequencing, the4^#mightbe Delftia acidovorans，the8^#minght be Stenotrophomonas maltophilias and the Y^#minghtbe Streptomyces griseolus. And the yield of ε-pL for flask fermentation of the three strainsreached at0.757,0.751and0.808g/L respectively, the yield of ε-pL of Y^#was the highestone, and it was selected.（3） The Y^#strain was mutagenic treated by nitrosoguanidine （NTG），and during thetreatment process, the final concentration of NTG was1.5mg/mL based on the experimentfor the selection of positive mutation and the mutagenic treatment for time was60minutes,the mortality rate reached on96.25%. And then, the Y^#has been treated under the aboveconditions and the high yield of ε-pL mutain strain numerded K-6was got, it’s production ofε-pL reached at0.854g/L. Finally, the stability of K-6was inspected by four times passagedculture, and the result achieved the desired objectives.（4） The flask fermentation conditions of K-6was researched through single factor andorthogonal experiments, and the optimized condition was obtained that the initial pH7.0,inoculum size of6%, the liquid volume20mL/100mL and the fermentation temperature was30℃. And optimized the fermentation medium components under this condition through theresponse surface optimization analysis method, and it was got the optimum fermentationmedium components: glucose,（NH₄）₂SO₄, yeast extract and MgSO₄·7H₂0were respectively40.00,12.00,7.00,0.30g/L. Three verification experiments has been done, the yield of ε-pLwas0.889g/L and it was very closed to the predictive value of0.895g/L, it showed that themodel could kindly predict the actual fermentation conditions. The yield of ε-pL was increased ultimately from0.808g/L to0.889g/L, and the yield increased by10.02%, throughthe optimization of fermentation conditions and the fermentation medium components. Thisresearch pave the way for the further breeding of ε-pL producing strains.