Breeding Of ε-polylysine-producing Strain And Studies On Batch Fermentation

ε-poly-L-lysine (ε-PL) is a homo-poly-amino acid characterized by the peptide bond between theα-carboxyl andε-amino groups of the essential amino acid L-lysine.ε-PL shows a wide range of antimicrobial activity against most gram-positive and gram-negative bacteria, fungi and also some viruses, and is stable and safe. Due to its antimicrobial activity,ε-PL is widely used as a food preservative. Hitherto, the industrialized production ofε-PL has only been carried out in Japan.In the article,Kitasatospora sp.PL6-3 was considered as a tool of production,in order to improve the productivity ofε-PL and optimize the process of batch fermentation in 5L fermentation.An AEC resistant mutant, Kitasatospora sp. MY5-36, was derived from Kitasatospora sp. PL6-3 by DES treatment. The mutant strain was selected on the agar plate containing 6 mg/mL S-(2-aminoethyl)-L-cysteine(AEC). The MY5-36 producedε-PL 1.17 g/L in flask, which was 3-fold in comparison with that of the original strain PL6-3. In order to investigate the genetic stablility,the mutant was test afer five continuous inoculation. The result showed that the mutant could transfer the genetic information to the son generation.Also, the characters of the MY5-36 were studied in this work. The morphological properties of MY5-36 changed a lot on the color of mycelium and spores. The color of spores changed from grey to white,and the back of colony changed from grey to golden yellow.Further more, the effects of stirring speed, ventilation volume and pH on MY5-36 fermentation in a 5L automatic jar were investigated. The researches showed that the stir velocity and pH played important roles in the fermentation. The optimum condition is 400r/min, 2L/min, and pH4.0. Batch fermentation ofε-PL in 5L bioreactor was carried out in the optimum culture conditions, the biomass was 7.69g/L, and the yield ofε-PL production was 7.72g/L, which was 7-fold higher than that of the parent strain. With the feeding of glucose,ε-PL productivity could reach as high as 13.9g/L.