酒精-沼气双发酵耦联工艺中非偏好型氮源尿素强化酒精发酵的生理过程机制

The fermentation industry is facing the problems of huge water consumption, wastewater production and treatment cost. To solve these problems, the fermentation ecological engineering proposed by us provides a novel idea, which has been successfully applied to cassava ethanol fermentation, constructing an integrated ethanol-methane fermentation process. When this process was studied, we found that the digestate contained high concentration of ammonia which is one important member in the central nitrogen metabolism and preferred nitrogen source for Saccharomyces cerevisiae. However, under this nitrogen source, growth of S. cerevisiae and ethanol fermentation was inferior to the non-preferred nitrogen source urea. To understand the mechanism that caused this phenomenon, metabolic regulation of S. cerevisiae under urea and ammonia was compared in terms of intracellular energy, redox equilibrium, global proteins expression and metabolic flux by the combination of iTRAQ mediated shotgun proteome strategy and 13C metabolic flux analysis to find the key different regulatory sites. The mechanism presented here not only gain improved insight into metabolic regulation of S. cerevisiae using nitrogen source, but also may provide a new strategy to optimize the integrated ethanol-methane fermentation process by obtaining the desired S. cerevisiae strain through metabolic engineering.

水耗量大、废水量多、废水处理成本高是发酵工业正面临的突出问题。对此，本课题组构建的“发酵生态工程学”诠释了一条全新的解决思路，并且已在木薯酒精生产上应用，建立了“酒精-沼气双发酵耦联工艺”，彻底解决了水耗和废水处理问题。申请人在对该工艺研究过程中发现：沼液中含有丰富的氨，而氨作为核心氮代谢途径的重要组成成分，是酿酒酵母的偏好型氮源。但是在此氮源下，酿酒酵母的生长和酒精发酵情况却劣于非偏好型氮源尿素。因此，本项目利用iTRAQ相对定量蛋白质组学技术和13C代谢通量分析等研究策略，从能量水平、氧化还原平衡，全局蛋白质表达和代谢通量层面，比较尿素和氨对酿酒酵母代谢调控的影响，找到关键调控差异位点，阐明尿素强化酒精发酵的生理过程机制。研究结果有助于为酿酒酵母的氮源代谢调控提供新的认识，并为酒精-沼气双发酵耦联工艺中酿酒酵母的代谢工程改造以优化工艺提供理论指导，具有重要的理论和实践意义。

水耗量大、废水量多、废水处理成本高是发酵工业正面临的突出问题。对此，本课题组构建的“发酵生态工程学”诠释了一条全新的解决思路，并且已在木薯酒精生产上应用，建立了“酒精-沼气双发酵耦联工艺”，彻底解决了水耗和废水处理问题。申请人在对该工艺研究过程中发现：沼液中含有丰富的氨，而氨作为核心氮代谢途径的重要组成成分，是酿酒酵母的偏好型氮源。但是在此氮源下，酿酒酵母的生长和酒精发酵情况却劣于非偏好型氮源尿素。因此，本项目利用转录组学技术和代谢组学等研究策略，从能量水平、氧化还原平衡，全局基因转录和代谢通量层面，比较尿素和氨对酿酒酵母代谢调控的影响，找到关键调控差异位点，阐明尿素强化酒精发酵的生理过程机制。研究结果有助于为酿酒酵母的氮源代谢调控提供新的认识，并为酒精-沼气双发酵耦联工艺中酿酒酵母的代谢工程改造以优化工艺提供理论指导，具有重要的理论和实践意义。