Objective      To establish the optimal high cell-density fermentation conditions of recombinant engineering bacterium pET32a-CR1-SCR15-18/BL21(DE3) for large scale production.     Methods      Based on the experimental results obtained in culture bottle

the cells were transferred to fermenter culture. The effects of the culture medium

temperature

pH value

concentrations of IPTG

activation time

and induction time were analyzed and optimized.      Results      The bacterium was activated in modified M9-CA medium at 37 ℃ for 4 h and then induced for another 4 h in the presence of 0.2 mmol /L IPTG. Glycerol was chosen as carbon source. The flow rates of feeding at the growth and induction phases were kept at the speeds of 40 ml/h and 70 ml/h

respectively. The culture’s pH value was maintained at 7.5 by adding  ammonia water

while dissolved oxygen was controlled about 40% by regulating rotating speed. Under the optimal conditions mentioned above

a highest yield of over 40 g/L SCR15-18 protein was achieved

accounting 28% of the total bacterial protein.     Conclusion      Higher density fermentation significantly improves the production of engineering bacteria and the expression level of CR1-SCR15-18 protein.