NH_(4)^(+)双阶段发酵控制谷氨酸工艺研究

Study on the Process of Controlling Glutamic Acid by NH_(4)^(+)Two-Stage Fermentation

为了缓解L-谷氨酸发酵过程中由于流加氨水调节pH所带来的高浓度NH_(4)^(+)抑制作用的问题,提出了NH_(4)^(+)双阶段发酵控制工艺。NH_(4)^(+)双阶段发酵控制工艺是指在L-谷氨酸发酵过程中采用NaOH和氨水的混合液代替氨水进行pH的调节,同时根据不同阶段NH_(4)^(+)浓度的需求调整NaOH与氨水的混合比例,使其最适于L-谷氨酸发酵。通过实验发现,发酵开始时采用NaOH和氨水摩尔混合比例为1∶7的调节液,发酵19 h后采用NaOH和氨水摩尔混合比例为1∶3的调节液代替氨水进行pH的调节,对于L-谷氨酸发酵提升效果最好,在此条件下最大OD_(600)达到了63,较基础发酵提高了23.5%,最终的菌体量为58,提高了52.6%,下降幅度为5,降低了61.5%,L-谷氨酸最终产量为171 g/L,提高了11.8%,糖酸转化率也由60.2%提高到了61.6%,同时对其代谢流进行分析后发现,L-谷氨酸代谢流提高了3.9%,L-丙氨酸、L-赖氨酸和乳酸代谢流分别降低了21.7%、21.5%和24.7%。NH_(4)^(+)双阶段发酵控制有利于提高菌体的活力和产酸性能,对于谷氨酸行业的精细化控制具有借鉴意义。

In order to alleviate the problem of high NH_(4)^(+)concentration inhibition caused by the adjustment of pH by adding ammonia water during the fermentation of L-glutamic acid,a NH_(4)^(+)two-stage fermentation control process is proposed.The NH_(4)^(+)two-stage fermentation control process refers to the use of a mixture of NaOH and ammonia water in the L-glutamic acid fermentation process to replace ammonia water for pH adjustment.At the same time,the mixing ratio of NaOH to ammonia water is adjusted according to the needs of NH_(4)^(+)concentration at different stages to make it most suitable for L-glutamic acid fermentation.It is found that the adjustment solution with a molar mixing ratio of NaOH to ammonia water of 1∶7 is used at the beginning of the fermentation,and the adjustment solution with a molar mixing ratio of NaOH to ammonia water of 1∶3 is used after 19 hours'fermentation to replace the ammonia water for pH adjustment,which has the best effect on the fermentation of L-glutamic acid.Under these conditions,the maximum OD_(600) reaches 63,which increases by 23.5%compared to the basic fermentation,the final cell mass is 58,which increases by 52.6%,and the decrease range is 5,decreasing by 61.5%.The final output of L-glutamic acid is 171 g/L,increasing by 11.8%,and the sugar-acid conversion rate increases from 60.2%to 61.6%.At the same time,after analyzing its metabolic flow,it is found that the metabolic flow of L-glutamic acid increases by 3.9%,and the metabolic flow of L-alanine,L-lysine and lactic acid reduces by 21.7%,21.5%and 24.7%respectively.The NH_(4)^(+)two-stage fermentation control is beneficial to improving the activity and acid production performance of the bacteria,and has reference significance for the precise control of glutamic acid industry.