优化细胞自絮凝强化生物炼制生产强度和产物浓度及生物量低成本采收

生物质可再生且环境友好，对可持续发展具有重要意义。然而，生物炼制过程生产强度低和产物浓度低的问题突出，不仅导致反应器容积规模大，设备投资高，而且产品分离能耗高并产生大量废水。此外，微藻作为第三代生物炼制原料，大规模培养后采收成本高是制约其开发利用的瓶颈。细胞密度低是反应器生产强度低的主要原因，而产物对细胞强抑制制约其浓度提高。细胞自絮凝不仅可以在反应器中自固定化提高细胞密度，而且细胞对高浓度产物抑制耐受性显著增强，同时还可以实现自沉降采收。. 本项目以乙醇发酵性能优良自絮凝酿酒酵母和运动发酵单胞菌为真核和原核微生物模式体系，解析细胞自絮凝及导致环境胁迫耐受性增强分子机制，建立改造非絮凝菌株，赋予可控自絮凝表型的平台技术，进而在分子、细胞、群体和过程工程多尺度调控优化细胞自絮凝，为解决生物炼制过程生产强度低和产物浓度低及微藻大规模培养后采收成本高突出问题创新技术开发，奠定科学基础。

Biomass resources are renewable and environmentally friendly. However, low productivity and product titer associated with biomass conversion make the biorefinery not economically competitive. Low cell density within bioreactors and inhibitory effect on microbial cells exerted by elevated product titer are root reasons for these phenomena. When self-flocculated, not only are cells self-immobilized within bioreactors for high density to improve productivity, but most importantly their tolerance to product inhibition is significantly improved, and high product titer can thus be achieved. In addition, cells can be recovered by cost-effective sedimentation, which is significant for large scale production of microalgae as feedstock for biorefinery.. In this project, self-flocculating Saccharomyces cerevisiae and Zymomonas mobilis are selected as model systems for eukaryotic and prokaryotic microbes, and molecular mechanism underlying their self-flocculation and enhanced tolerance to product inhibition associated with the morphological change will be investigated. Genes responsible for their self-flocculation will be mined from the genomics with functional FLO genes identified, and their expression and regulation controlled at genetic and epigenetic levels will be further elucidated for genetic manipulations. It is hypothesized that the improved tolerance of microbial cells to product inhibition and other environmental stresses is due to enhanced quorum sensing (QS), since the self-flocculation of microbial cells provides extremely high local cell density, and in the meantime creates a unique microenvironment for more efficient transport of signal molecules and signal transduction as well, which will be examined experimentally by identifying signal molecules that mediate the QS process and stress response. At the end, platforms for engineering microbial cells with the self-flocculating phenotype will be established, which would lay a foundation for developing novel technologies to improve productivity and product titer for biorefinery processes as well as harvest microalgae cost-effectively as the potential feedstock for biorefinery.