摘要
The properties of the screened mutants for hyper-production of citric acid induced by carbon （12C6＋） ion beams and X-ray irradiation were investigated in our current study. Among these mutants, mutant H4002 screened from 12C6＋ ion irradiation had a higher yield of citric acid production than the parental strain in a 250-ml shaking flash. These expanded submerged experiments in a bioreactor were also carried out for mutant H4002. The results showed that （177.7-196.0） g/L citric acid was accumulated by H4002 through exploiting corn meal hydrolysate （containing initial 200.0-235.7 g/L sugar） with the productivity of （2.96-3.27） g/（L.h）. This was especially true when the initial sugar concentration was 210 g/L, and the best economical citric acid production reached （187.5±0.7） g/L with a productivity of 3.13 g/（L.h）. It was observed that mutant H4002 can utilize low-cost corn meal as a feedstock to efficiently produce citric acid. These results imply that the H4002 strain has the industrial production potentiality for citric acid and offers strong competition for the citric acid industry.
研究目的：研究高产黑曲霉突变菌株以玉米粉为原料的生物反应器扩大发酵，以期获得适合于工业化生产柠檬酸的发酵工艺。创新要点：以玉米粉为原料，系统地研究了筛选得到的高产菌株在50L生物反应器中不同糖浓度发酵生产柠檬酸的特性，最终优化出适合于工业化生产柠檬酸的发酵工艺。研究方法：（1）利用淀粉酶对粉碎后的玉米进行液化，然后过滤，最终得上清液；（2）以50L生物反应器作为发酵设备，对筛选得到的高产柠檬酸菌株进行扩大培养；（3）通过测定不同培养时期中积累的柠檬酸含量和剩余的残总糖，最终优化出高效率生产柠檬酸的发酵工艺。重要结论：以不同糖浓度的液化玉米粉上清液作为碳源，突变菌株H4002能积累177．7--196．0g，L的柠檬酸，效率能达到2．96～3．27g/（L·h），尤其当糖浓度为210g／L，H4002菌株表现出最佳的柠檬酸生产水平，如柠檬酸积累187．5g/L，生产效率达3．13g／（L·h）。上述结果说明了突变菌株H4002拥有快速生产柠檬酸的能力。
基金
supported by the Agriculture Science and Technology Achievement Transformation Fund of Science and Technology Ministry of China(Nos.2013GB24910680 and 2012GB24910647)
