Improvement of Vitamin K ₂ Production by Escherichia sp. with Nitrogen Ion Beam Implantation Inductio

Low-energy ion implantation as a novel mutagen has been increasingly applied in the microbial mutagenesis for its higher mutation frequency and wider mutation spectra. In this work, N ⁺ ion beam implantation was used to enhance Escherichia sp. in vitamin K ₂ yield. Optimization of process parameters under submerged fermentation was carried out to improve the vitamin K ₂ yield of mutant FM5-632. The results indicate that an excellent mutant FM5-632 with a yield of 123.2±1.6 µg/L, that is four times that of the original strain, was achieved by eight successive implantations under the conditions of 15 keV and 60×2.6×10¹³ ions/cm² . A further optimization increased the yield of the mutant by 39.7%, i.e. 172.1±1.2 µg/L which occurred in the mutant cultivated in the optimal fermentation culture medium composed of (per liter): 15.31 g glycerol, 10 g peptone, 2.89 g yeast extract, 5 g K ₂ HPO ₄, 1 g NaCl, 0.5 g MgSO ₄ ·7H ₂ O and 0.04 g cedar wood oil, incubated at 33 ^o C, pH 7.0 and 180 rpm for 120 h.