生物基化学品的糖析萃取动力学及其耦合发酵研究

The prominent problems for separation of bio-based chemicals from fermentation include too many steps, low yield of target product, much energy consumption, and great environmental pressures. Based on the previous research about salting-out extraction of bio-based chemicals, sugaring-out extraction was postulated to set up an integrated process of solid-liquid separation and extraction of target product, in which most of macromolecules and some part of by-products were removed, the residul subatrate and some part of by-products would be recycled. Sugaring-out extraction is a promising technique to solve the difficulty in separation of bulk fermentation-based chemicals. In this project, the bio-based chemicals, such as 2,3-butadiol and lactic acid, were used as target products to investigate their sugaring-out extraction using infrared spectroscopy. The rule of forming phase for the mixing sugaring- and salting-out systems would be discussed in partition behaviors of targets, by-products, cells, macromolecules, residul substrate, and pigments. The optimal conditions of sugaring-out extraction were determined for different targets. The extraction kinetics would be also investigated. An integrated process of fermentation and extraction could be set up by using the bottom phase of extraction as substrate for fermentation. After systematic and deep research, sugaring-out extraction would be developed to become a novel, normal, and effective technology for separation of bio-based chemicals.

生物基化学品的分离过程面临步骤多、收率低、能耗高、废水处理量大等突出问题。在前期开展的盐析萃取分离基础上，提出用发酵培养基中的糖和盐进行糖析萃取分离目标产物的思路，将固-液分离、大分子除杂和部分副产物分离集成于萃取过程，并将萃取与发酵耦合，显著减少废水的排放，实现残余底物和副产物的再利用。本课题以2,3-丁二醇和乳酸为分离研究对象，利用衰减全反射傅里叶变换红外光谱在线检测技术，深入探讨糖析-盐析混合萃取体系的成相规律，揭示复杂发酵系统中目标产物、副产物、细胞、大分子杂质、残余底物、色素等的分配行为和萃取动力学，确立糖析萃取的最佳体系和条件（如pH、温度），考察萃余相去除溶剂后用于再次发酵的可行性，建立同步糖化发酵-萃取耦合的集成工艺，考察影响细胞生长和代谢的因素，在线研究新过程的发酵动力学。期望通过系统深入的研究，将糖析萃取技术开发成为一种适合于发酵产品的新型、普适、高效的分离技术。

以可再生的生物质资源为原料生产各种生物基化学品是一种绿色生物制造技术。与化学法生产相比，发酵液成分复杂、水溶性好、沸点高、产物浓度低、固液分离困难，因此下游分离是生物基化学品产业化的瓶颈。.本项目基于目标产物在糖/盐与短链醇等有机溶剂形成的两相中分配差异，实现生物基化学品的糖析/盐析萃取。首先考察了糖/盐与短链醇/酯/离子液体的成相规律，绘制了相图，用Merchuk、Othmer-Tobias、Bancroft等经验方程描述系线与双结点等成相规律，并考察了少量盐对糖析萃取体系成相的影响。其次研究了目标产物（1,3-丙二醇、2,3-丁二醇、乙偶姻、乳酸、琥珀酸等）及其发酵液中细胞、蛋白、副产物、残余底物、色素等在糖析/盐析萃取体系中的分配情况（分配系数、产物收率、细胞和杂质去除率等），同时考察了发酵液浓度、萃取剂和糖的浓度、添加培养基无机盐（硫酸铵、磷酸氢二钾等）、体系pH值和温度对分配行为的影响。最后研究了萃余相回收有机溶剂后用于发酵的可行性，考察了糖相中残余溶剂对微生物生长和代谢的影响。考察发酵过程中细胞生长、底物消耗、产物形成的规律，分析代谢流量分布。.研究表明，利用糖/盐与有机溶剂形成的两相以及目标产物在两相分配的差异，可以实现产物有效的糖析萃取，并能与发酵进行耦合。例如用叔丁醇/葡萄糖体系萃取发酵液中的2,3-丁二醇、乙酸乙酯/葡萄糖体系萃取3-羟基丁酮、异丙醇/葡萄糖体系萃取乳酸等。大部分产物分配在上相，富含糖的下相可用于再次发酵，从而减少了废水的排放。.研究成果发表34篇学术论文，其中SCI论文25篇，在分离领域权威期刊Separation and Purification Technology上发表9篇论文。授权中国发明专利6项，申请发明专利7项。项目培养博士研究生6名，硕士研究生9名，其中2名博士已经毕业，8名硕士已经毕业，4名博士生和1名硕士生在读。