Abstract: The effects of different rare earth ions and coordination compounds on the synthesis of 2-keto-L-gulonic acid (2-KLG) by mixed culture of Bacillus megaterium and Ketogulonigenium vulgare were investigated in the two-step fermentation of vitamin C. The results indicated that the proper promotion concentrations of various rare earth ions were all about 5 mmol/L. Furthermore, the low concentration caused 2-KLG synthesis promotion while high concentration caused 2-KLG synthesis inhibition. EDTA-La and lanthanum citrate inhibited 2-KLG synthesis, but lanthanum oxalate promoted it at a concentration of 1 mmol/L and enhanced the final production of 2-KLG by 6.4%. The cell growth conditions at the mid- and late fermentation stages were remarkably improved with the addition of 5 mmol/L La3+. 2-KLG ultimate output was increased and the fermentation time reduced at the same time. When 5 mmol/L La3+ was fed to 3.6 L fermentor for batch fermentation, the L-sorbose consumption rate and 2-KLG productivity were increased by 12.4% and 14.8% compared with that of the control, respectively. And the fermentation time was declined by 11.1%.

Key words: two-step fermentation, rare earth ions, 2-keto-L-gulonic acid, rare earth complex

摘要： 采用普通生酮基古龙酸菌(Ketogulonigenium vulgare)与巨大芽孢杆菌(Bacillus megaterium)混合菌系，研究了不同稀土离子及其配合物对发酵生产维生素C前体物质2-酮基-L-古龙酸(2-KLG)的影响. 结果表明，各稀土离子对2-KLG合成的最佳促进浓度均约为5 mmol/L，且具有低浓度促进、高浓度抑制的作用规律. EDTA镧、柠檬酸镧均抑制2-KLG的合成，而1 mmol/L草酸镧对其合成代谢有促进作用，使其产量提高6.4%. 摇瓶中添加5 mmol/L La3+，发酵中后期菌体生长状况得到显著改善的同时提高了2-KLG最终产量并缩短了发酵周期. 3.6 L发酵罐中添加5 mmol/L La3+进行分批发酵，平均山梨糖消耗速率和2-KLG生产强度比对照分别提高12.4%和14.8%，发酵周期缩短11.1

关键词: 二步发酵, 稀土元素, 2-酮基-L-古龙酸, 稀土配合物