Design of a Packed-Bed, Continuous-Flow Fermentation Process Tailored for Cellulosic Ethanol Production

PI：Hedden，Ronald Institution：德克萨斯理工大学提案编号：1066616标题：为纤维素乙醇生产量身定做的填充床连续流发酵过程的设计从木质纤维素生物质中提取的乙醇(Etoh)是未来汽车能源需求最有前途的替代燃料之一。然而，必须降低生产纤维素乙醇的成本，才能使其与汽油或从玉米和甘蔗等作物中提取的乙醇竞争。通过提高每单位原料的乙醇产量和降低工业化规模发酵的资本设备和运营成本，可以改善工艺经济性。用连续流动固定化细胞反应器(ICR)取代间歇发酵罐，可以大大降低资本设备和运营成本，由于更高的原料转化效率和更高的体积生产率，ICR可以显著减小规模。该项目致力于设计ICR工艺，利用新型合成多孔性聚合物支架(SPPS)部分固定细胞，用于通过重组乙醇胺生产纤维素乙醇。初步结果表明，用SPPS材料填充的连续流柱反应器的体积生产率至少可以达到同类间歇发酵的14倍，而SPPS床的多孔结构解决了限制传统凝胶固定化系统的二氧化碳滞留问题。对两种填充床ICR设计的性能进行了比较：短立柱反应器和带填充床段的搅拌槽式反应器。PI还将优化用于发酵纤维素原料的SPPS材料的特性(孔尺寸、孔体积分数和颗粒尺寸)。这项研究将系统地优化适用于任何ICR发酵的多孔聚合物材料。最初的研究将集中在大肠杆菌菌株LY01，因为它的比生长率很高，尽管这种ICR设计应该同样适用于产乙醇菌的酿酒酵母或运动发酵单胞菌。这项研究将使用可以代谢己糖和戊糖的转基因生物，专门研究将纤维素衍生的原料转化为乙醇的ICR系统。在用“真正的”纤维素原料测试反应器性能之前，将用简单的糖混合物系统地研究有机抑制剂对体积生产率的影响。将开发一个反应堆性能的分析模型，以实现对参数变化影响的综合理解。细胞密度将使用表达绿色荧光蛋白(GFP)的工程大肠杆菌LY01进行研究。这项研究解决了连续流动发酵罐的设计，这些发酵罐经过优化，可以处理特定于纤维素乙醇的问题：饲料中的抑制剂和颗粒物，以及二氧化碳通风。更广泛的影响这项研究为社会带来了好处，因为它有潜力为利用可再生的非食品资源生产燃料提供变革性的新工艺技术。这项研究将产生新的知识，这些知识可能会使发展中的纤维素乙醇工业在经济上受益。该项目对于PI在德克萨斯理工大学建立化学工程方面的教育和推广计划，以及支持材料和可再生能源研究与化学工程教育的整合至关重要。国际和平协会和联合国际组织历来支持涉及高中生和本科生的外联活动，其中包括妇女和代表人数不足的群体的成员。通过荣誉学院的本科生研究奖学金计划和德克萨斯理工大学的康菲石油桥梁计划，本科生将与研究生一起为单元操作教学实验室设计生物技术实验。参与培训的两名研究生将通过德克萨斯理工大学默多工程专业中心完成工程伦理培训。学生将通过学习发酵罐中使用的多孔聚合物来获得中子散射方法和辐射安全方面的培训。结果将通过在国家和国际会议上的介绍以及关于纤维素乙醇的教育网页传播，该网页将介绍这些研究工作。

PI: Hedden, Ronald Institution: Texas Tech University Proposal Number: 1066616Title: Design of a packed-Bed Continuous-Flow Fermentation Process Tailored for Cellulosic Ethanol ProductionIntellectual MeritEthanol (EtOH) derived from lignocellulosic biomass is among the most promising alternative fuels for future automotive energy needs. However, reductions in the cost of producing cellulosic EtOH must be realized in order to make it competitive with gasoline or EtOH derived from crops such as corn and sugarcane. Process economics can be improved both by increasing the EtOH yield per unit of raw materials and by lowering capital equipment and operating costs for industrial-scale fermentations. Capital equipment and operating costs can be lowered tremendously by replacing batch fermentors with continuous-flow, immobilized cell reactors (ICR), which can be significantly smaller due to higher feedstock conversion efficiency and higher volumetric productivity. This project addresses the design of ICR processes tailored for production of cellulosic EtOH by recombinant ethanologens, using novel synthetic porous polymer scaffolds (SPPS) to partially immobilize the cells. Preliminary results show that a continuous-flow column reactor packed with an SPPS material can achieve volumetric productivity at least 14 times higher than that of a comparable batch fermentation, while the porous structure of the SPPS bed mediates problems with CO2 holdup that limit conventional gel-immobilized systems. The performance of two packed bed ICR designs will be compared: a short vertical column reactor and a stirred tank reactor with packed bed section. The PIs will also optimize characteristics of the SPPS materials (pore size, pore volume fraction, and particle size) for fermentation of cellulose-derived feedstocks. This study will systematically optimize porous polymer materials for any ICR fermentations. The investigation will initially be focused on E. coli strain LY01, due to its high specific growth rate, though this ICR designs should be equally applicable to ethanologenic strains of Saccharomyces cerevisiae or Zymomonas mobilis. This study will examine ICR systems specifically for conversion of cellulose-derived feedstocks to EtOH, using genetically modified organisms that can metabolize both hexoses and pentoses. The effects of organic inhibitors on volumetric productivity will be systematically examined with simple sugar mixtures before testing reactor performance with "real" cellulose-derived feedstocks. An analytical model of reactor performance will be developed to achieve an integrated understanding of the effects of parametric variations. Cell density will be studied using E. coli LY01 engineered to express green fluorescent protein (GFP). This study address the design of continuous-flow fermentors that are optimized to handle issues specific to cellulosic EtOH: inhibitors and particulate matter in the feed, and CO2 ventilation. Broader ImpactThis research offers a benefit to society due to its potential to provide transformative new process technology for production of fuels from renewable non-food resources. The research will generate new knowledge that can potentially benefit the developing cellulosic EtOH industry economically. The project is vital to the PI's efforts to establish educational and outreach programs in Chemical Engineering at Texas Tech, and to support integration of materials and renewable energy research with Chemical Engineering education. The PI's and co-PI's groups have historically supported outreach activities involving high school and undergraduate students, including women and members of underrepresented groups. Through the Undergraduate Research Fellowship program in the Honors College and the ConocoPhilips Bridge program at Texas Tech, undergraduate students will work with graduate students to design biotechnology experiments for the Unit Operations teaching laboratory. Two graduate students involved will complete training in Engineering Ethics through the Murdough Center for Engineering Professionalism at Texas Tech University. Students will acquire training in methods of neutron scattering and radiation safety by studying porous polymers used in fermentors. Results will be disseminated through presentations at national and international meetings and through an educational webpage regarding cellulosic EtOH, which will feature these research efforts.