在不同初始生物素添加量的条件下进行谷氨酸发酵实验,探讨生物素对谷氨酸棒杆菌分泌谷氨酸的影响机制。实验结果表明:生物素浓度是控制胞内谷氨酸向胞外分泌的关键因素,生物素浓度进入亚适量范围后胞内谷氨酸开始向胞外分泌,名义生物素"亚适量"的浓度范围在1.97～2.29μg/g DCW。在菌体胞内谷氨酸正常向外分泌时添加20μg/L的生物素,谷氨酸正常向外分泌即停止,胞内谷氨酸浓度增加,进一步证明谷氨酸分泌受生物素浓度控制。通过胞内、胞外谷氨酸浓度对比及生物素所起的作用,提出了谷氨酸分泌的一种新的假定模式——"生物素浓度触发式分泌"模式。

The glutamic acid fermentation was carried out under different initial biotin concentration to investigate the effect of biotin on glutamic acid secretion.The results indicated that biotin concentration was the key factor to control glutamic acid secretion.The secretion of Glutamic acid was started when the concentration of biotin was within 1.97～2.29 μg/g DCW of "nominal biotin-limitation".The glutamic acid secretion was immediately terminated when 20μg/L biotin was supplemented during glutamic acid secretion.After that the intracellular glutamic acid began to increase which further indicated that glutamic acid secretion was controlled by biotin concentration.A new assumed secretion mode-"biotin concentration trigger secretion" was proposed through the comparison of intracellular and extracellular glutamic acid concentrations.