为解决谷氨酸棒杆菌发酵产异亮氨酸适应期较长,菌体细胞膜通透性差,异亮氨酸分泌速率慢的问题,实验通过在发酵罐内安装超声棒,探究超声对谷氨酸棒杆菌整个发酵过程中生物量及产酸的影响。研究从超声周期、超声功率、超声频率、超声时间和超声模式5个方面,探究了菌体生物量及产酸的最优条件。结果表明,使用80 W/L、18 kHz的超声波,在菌体适应期、对数生长期及平稳期分别超声2、6、1 h,超声模式设置为开10 s、停30 s,菌体发酵适应阶段缩短至2 h以内,菌体快速进入对数生长期,且对数生长期从2 h延续到24 h, 直至40 h结束菌体活力依旧很强,最终菌体干重达到了41.0 g/L,比未超声提高了74.5%;L-异亮氨酸产量达到了39.0 g/L,比未超声产酸量提升了69.6%。超声产生的微扰动有利于细胞增殖,同时产生的机械剪切作用增加了细胞膜的通透性,提高了产酸能力。
In order to solve the problems of long adaptation period for the production of isoleucine fermented by Corynebacterium glutamate, poor membrane permeability of the cells, and slow isoleucine secretion rate, the influence of ultrasound on the biomass and acid production of C. glutamate during the whole fermentation process was explored by installing ultrasonic rods in the fermentation tank. The optimal conditions for biomass and acid production were obtained by a comprehensive equilibrium analysis method from five aspects including ultrasonic cycle, ultrasonic power, ultrasonic frequency, ultrasonic time and ultrasonic mode. Results showed that when treated with 80 W/L, 18 kHz ultrasonic for 2, 6 and 1 h, in the adaptation, logarithmic and stable phase, respectively, with an ultrasonic mode of 10 s on and 30 s off, the fermentation adaptive phase reduced to less than 2 h. C. glutamate quickly entered the logarithmic phase, and the logarithmic phase prolonged from 2 h to 24 h, the strain vitality remained strong at the end of 40 h. The cell dry weight was 41.0 g/L, increased by 74.5% compared with that without ultrasonic. The yield of L-isoleucine reached 39.0 g/L, which was 69.6% higher than that of non-ultrasonic acid. Microperturbation induced by ultrasound is beneficial to cell proliferation, and mechanical shearing increases membrane permeability and acid production capacity.
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