Improvement of Vitamin K 2 Production by Escherichia sp. with Nitrogen Ion Beam Implantation Inductio
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LIU Yan (刘艳),
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WANG Li (王丽),
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ZHENG Zhiming (郑之明),
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WANG Peng (王鹏),
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ZHAO Genhai (赵根海),
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LIU Hui (刘会),
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GONG Guohong (贡国鸿),
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WU Hefang (吴荷芳),
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LIU Hongxia (刘红霞),
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TAN Mu (檀沐),
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LI Zhemin (李哲敏)
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Abstract
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.
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