Breeding of High ε-poly-L-lysine-producing Strain by Streptomycin Resistance
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Abstract:
Using a ribosome engineering-based breeding approach, the ε-Poly-L-lysine (ε-PL) biosynthesis capability of Streptomyces albulus M-Z18 was gradually enhanced by increasing streptomycin resistance in a stepwise manner. Firstly, the ε-PL production by S. albulus M-Z18 was increased from 1.6 to 2.43 g/L through screening low streptomycin-resistant (1~5 MIC) mutant strains. Subsequently, the streptomycin tolerance was further increased (5~10 MIC), to enhance ε-PL biosynthesis capability. Finally, a high ε-PL-producing mutant S. albulus SS-19 was obtained, with the yield of ε-PL and the unit cell synthesis capability as 3.13 g/L and 0.58 g/g, respectively, which were increased by 95.63% and 137.61%, respectively, compared with the original strain M-Z18. Results showed that the activities of the key enzymes involved in the central carbon metabolic pathway and ε-PL biosynthesis pathway were significantly enhanced, suggested that the anabolic metabolism of ε-PL was significantly enhanced. In the RSM medium with glucose as the carbon source, S. albulus SS-19 exhibited a greater ε-PL biosynthesis capability compared with the high-yield strains obtained from previous breeding. The above results indicated that the ε-PL production by Streptomyces albulus could be improved effectively by the screening method involving the gradual increase of streptomycin resistance.
