大肠杆菌跨膜电子转换通道构建及电合成丁二酸调控

Nowadays, it has a great interest in converting electron to reducing power for chemical production using miciobial electrosynthesis. It was found that E.coli did not have the ablility for directly converting electron to reducing power when we used E. coli BA102 for succinic acid production in electrochemical reactor. Only if neutral red was used as electron mediator, electron could be converted to reducing power for succinic acid production by E.coli. However, because electron mediator showed damage for cell growth and part of reducing power was used for byproducts synthesis, efficiency for succinic acid electrosynthesis was low. Our objective in this project is to convert electron form electrode to reducing power for succinic acid production. By assembling electron transfer element form electrogenesis microbiology, electron converted channel with high suitability for E.coli will be constructed which could directly convert electron to cell membrane.Besides, interaction between electron and cell membrane and effects of electron on cell growth and metabolites distrbution will also be investigated. Furthmore metabloic network model will be set up for redesign electron metabolic pathway. Electron flux will be controlled for succinic acid production, and byproduct will be reduced. As a result, a recombinant E.coli will be constructed for electrosynthesis with high efficiency, and stragety for succinic acid electrosynthesis will be set up.

当前利用微生物电合成技术将电能转换为还原力合成化学品备受关注。本项目组在电化学装置中利用E. coli BA102合成丁二酸时发现，E. coli缺乏直接将电极提供的电子转换为还原力的能力；只有当添加中性红为电子介体时，E. coli才能利用电子作为还原力合成丁二酸。然而，由于电子介体对细胞的损伤以及电子转换的还原力在细胞内有部分流向副产物合成途径，导致电合成丁二酸效率低下。本项目以实现电极电子转换为丁二酸合成途径可利用的还原力为目标，通过组装来自于产电微生物的电子传递元件，构建在E.coli中具有高度适配性的电子转换通道，实现电子从电极至细胞内的直接传递；此外，通过电子与细胞膜相互作用关系及对细胞生长代谢的影响机制解析，结合代谢网络模型进行电子代谢途径再设计，控制电子在细胞内流向，减少副产物合成，提高电子利用效率。最终构建出高效电合成丁二酸的重组E.coli，并建立其电合成调控策略。

微生物电合成是近年来在微生物燃料电池基础上发展起来的新技术，利用电活性微生物从外界电极上获得电子，转换成细胞内还原力，从而实现利用电能合成化学品的目标。相对于其他电活性微生物，模式微生物从菌株改造到化学品合成都更为成熟。然而，在模式微生物中表达电子传递途径实现电合成化学品的研究还鲜有报道。本项目在E. coli中组装具有高度适配性的电子转换通道，实现了在无需外源添加氧化还原电子介体的微生物电化学系统中，电子从电极传递进入细胞内，E. coli实现了对外源电子的利用；解析了电子传递方式与E. coli细胞膜相互作用关系，阐明了胞外电子对细胞生长代谢的影响；构建高效的重组E. coli电合成丁二酸体系，优化了外源电子供给的环境条件，提高了电合成丁二酸的效率；在电化学系统中建立氧化还原电位(ORP)调控策略，优化体系中的电子供需平衡，达到对电合成丁二酸过程中电子的“按需供给”的效果，提高了胞外电子的供给效率。本项目的研究成果为微生物电合成还原性代谢产物的过程设计提供了思路与借鉴，为将电能向化学能转化的实践提供了理论基础。项目共发表SCI论文22篇，申请中国发明专利4项，参加国内外会议10人次，培养博士生2名，硕士生8名。