双菌发酵耦合渗透汽化分离的强化机制及乙醇丁醇高产策略研究

The main bottlenecks for bioethanol and biobutanol industrialization are the low conversion of cellulosic materials and the energy-intensive separation processes. More significantly, it could not effectively utilize the pentose fraction in cellulosic hydrolysate by Saccharomyces cerevisiae while the yield of butanol production from cellulosic sugars mixture is relatively low by Clostridium acetobutylicum. Besides, because of the severe end product inhibition of ethanol and acetone-buatnol-ethanol (ABE) fermentation processes, the solvent separation is remained difficulty and calls for improvements of the conventional processes. In this research, the Saccharomyces cerevisiae- Clostridium acetobutylium co-fermentation process was established and integrated with pervaporation under biorefinery concept. The fermentation performances as well as the utilization of cellulosic materials were improved by optimized the key parameters and the metabolic analysis of the twin-strain consortium. The kinetics of the integration process, and the metabolic flux and the transcriptomic analysis of the fermentation-pervaporation integration system were further practiced for clarify the intensification mechanism. This study showed promising in further improves the conversion efficiency of the lignocellulosic materials to bio-fuels.

纤维质生物燃料乙醇、丁醇产业化的主要瓶径为底物转化率低和分离能耗高。主要体现在酿酒酵母发酵产乙醇不能利用纤维糖底物中的戊糖；丙酮丁醇梭菌发酵产丁醇过程的糖底物溶剂转化率低，溶剂的产物抑制导致溶剂产物浓度低，分离难度大。本项目基于整体工艺的创新设计，以酿酒酵母-丙酮丁醇梭菌的双菌发酵过程为研究对象，构建双菌发酵耦合渗透汽化分离系统。通过对双菌发酵分离耦合系统调控和代谢解析，实现纤维乙醇、丁醇的高产，以及木质纤维素底物中纤维素和半纤维素的高效转化与利用。进而通过溶剂的生产-分离动力学分析，双菌发酵系统的碳主路代谢通量分析，转录组学分析等手段，探究双菌发酵-渗透汽化分离耦合过程的强化机制。本项目的研究将为进一步提高木质纤维素资源的能化转化效率奠定理论和技术基础。

本项目构建了酿酒酵母-丙酮丁醇梭菌级联发酵系统，并与渗透汽化原位分离技术耦合，以高效发酵-分离获得浓缩ABE溶剂。揭示了双菌发酵过程中的协同机制。系统性的评价了双菌发酵-渗透汽化耦合过程中的碳质流向和分离能耗，将制备吨混合溶剂的秸秆消耗量从传统ABE单菌发酵的约12吨干秸秆水平降低至双菌级联工艺的6吨干秸秆水平，显著降低了纤维乙醇、丁醇的原料成本。受酿酒酵母-丙酮丁醇梭菌级联系统启发，构建了丙酮丁醇梭菌-黏红酵母级联系统，实现发酵废水的回用与超低排放。评价了ABE原位分离溶剂对木质纤维素解聚过程的强化机制，在双菌发酵系统的基础上，开发预处理工艺与发酵-分离系统的整体耦合技术，促进了木质纤维素解聚和糖化转化。此外，为进一步提升双菌发酵-渗透汽化耦合系统经济性，提出若干生物炼制工艺，将耦合系统获得的ABE溶剂高值化转化，制备材料及精细化学品。开发了新的面向终产物精馏分离序列，依此进行多间壁塔分离的理论计算与模拟。