Medium Composition Suitable for l-Lysine Production by Methylophilus methylotrophus in Fed-Batch Cultivation

l-Lysine production was investigated in fed-batch fermentation using l-lysine producer of Methylophilus methylotrophus. By the addition of nutrient composition, containing l-methionine, K2HPO4, NaH2PO4, CuSO4·5aq, MnSO4·5aq, ZnSO4·7aq, FeCl3, MgSO4·7aq and CaCl2·2aq, in the feed medium, cell growth could be maintained through the cultivation, and l-lysine production reached to 7.86 g. In addition, the effect of counter ion for NH4+ (Cl−, SO42–, glutamate, succinate and citrate) was examined. The result showed that the cell growth in the medium using Cl− and glutamate were improved compared with that using SO42–, succinate and citrate, and l-lysine production in the medium using Cl− and glutamate reached to more than 9.0 g. In this experiment, there was a clear correlation between ionic strength and growth rate in the cultivation. In order to examine the influence of ionic strength on growth rate, the activity of enzymes in central metabolic pathway from methanol to pyruvate were assayed using samples at the log-phase and the stationary phase in fed-batch cultivation using (NH4)2SO4 and (NH4)Cl as ammonium source. It was found that the higher ionic strength inhibited methanol oxidation activity, which linked to cell growth. In this report, it was revealed that maintaining a relatively low ionic strength had a positive effect on l-lysine production using l-lysine producer of M. methylotrophus.