以玉米粉/废弃毕赤酵母为混合原料高效发酵丁醇

Effective butanol fermentation using corn starch and waste Pichia pastoris semi-solid mixture as the substrate

丙酮丁醇梭菌发酵生产ABE(丙酮-丁醇-乙醇)溶剂的传统原料是玉米淀粉,价格贵,生产基本亏损.重组毕赤酵母废弃物含有丰富的碳水化合物和蛋白质,有望替代淀粉原料.采用NaOH处理固态废弃毕赤酵母形成废酵母固/液悬浊液,发酵通过降低初始玉米粉用量并在ABE发酵进入到产溶剂期后添加废酵母悬浊液进行.对初始玉米粉用量、废酵母/NaOH投料量进行了优化,结果表明:它们的最佳用量分别为8%、80 g/L、6-10 g/L.在此条件下,100 mL厌氧瓶下的丁醇产量可以稳定在9.0-12.0 g/L的较高水平,比8%玉米粉培养基的对照提高80%-120%,与15%玉米粉培养基的对照基本持平;与对照组相比,总糖的利用效率可以从50%大幅提高到超过90%的水平;玉米粉用量可以节省57%以上;酵母废弃物最多有52%的碳水化合物可以有效地转化成气体/液体产物.本研究表明以玉米粉/废弃毕赤酵母为混合原料发酵丁醇,可以同时实现固体废物的资源化和减量化、淀粉原料的高效利用和节省化,提高了ABE发酵的综合经济性能.

Developing a novel corn starch and waste Pichia pastoris semi-solid mixture substrate system for the acetone–butanol–ethanol(ABE) fermentation process can increase the low sugar utilization yield of traditional ABE fermentation,save on the usage and costs of raw materials, and reduce the amount of waste P. pastoris semi-solid produced and increase its reutilization. Semi-solid waste yeast was treated with NaOH to form solid-liquid suspensions, and then the pH of the suspensions was restored to 5-6 using H2SO4. The initial corn starch content was reduced from 15 to 8% to start the fermentation, and then the pretreated suspensions were added to a broth, where the ABE fermentation was then induced to enter the solventogenesis phase(after ~24 h) by supplementing the suspension with a suspension:broth mixture with a volume ratio of 1:4. Fermentation was implemented either in 100 mL anaerobic bottles or in a 7 L anaerobic fermenter. The optimal initial doses of corn starch, waste yeast suspension, and NaOH to use were identified as 8%, 80 g/L, and 6-10 g/L, respectively. With this mixture-substrate system, the butanol concentration increased and stabilized around 9.0-12.0 g/L, which was 80%-120% higher than that obtained with an 8 or 15% corn starch-based substrate, the total sugar utilization yield was greatly increased from below 50% to more than 90%, more than 57% of corn starch was saved, and a maximum 52% of the carbohydrates in the waste yeast semi-solid could be effectively reutilized or digested for gasification/liquefaction. A novel corn starch-waste yeast semi-solid mixture substrate-based ABE fermentation process was proposed based on the results of this study. This system simultaneously consumed a maximum 52% of the carbohydrates in the semi-solid waste for the formation of gaseous or liquid products to reduce the amount of waste semi-solid produced, increased the total sugar yield from 50%(in controls) to over90%, stably maintained ABE/butanol concentrations of at least over 85% of the levels obtained using a 15% corn starch-based substrate, and saved over 57% of the expensive corn starch that would otherwise have to be used.