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

主要研究者：Hedden，罗纳德机构：德克萨斯理工大学提案编号：1066616题目：设计一种适合纤维素乙醇生产的填充床连续流发酵工艺知识产权来自木质纤维素生物质的乙醇（EtOH）是未来汽车能源需求最有前途的替代燃料之一。然而，必须实现生产纤维素EtOH的成本的降低，以使其与汽油或来源于作物如玉米和甘蔗的EtOH竞争。通过提高每单位原材料的EtOH产率以及降低工业规模发酵的资本设备和运营成本，可以提高工艺经济性。通过用连续流动的固定化细胞反应器（ICR）代替分批发酵罐，可以大大降低资本设备和操作成本，由于更高的原料转化效率和更高的体积生产率，ICR可以显着更小。该项目旨在设计ICR工艺，通过重组产乙醇菌生产纤维素EtOH，使用新型合成多孔聚合物支架（SPPS）部分覆盖细胞。初步结果表明，连续流柱反应器填充的SPPS材料可以实现体积生产率至少14倍高于可比的分批发酵，而多孔结构的SPPS床介导的问题与CO2滞留，限制传统的凝胶固定化系统。比较了两种填充床ICR反应器的性能：一种是短立式反应器，另一种是带有填充床段的搅拌釜式反应器。PI还将优化用于纤维素衍生原料发酵的SPPS材料的特性（孔径、孔体积分数和粒度）。本研究将系统地优化用于任何ICR发酵的多孔聚合物材料。调查将首先集中在E。大肠杆菌菌株LY01，由于其高比生长速率，尽管该ICR设计应同样适用于酿酒酵母或运动发酵单胞菌的产乙醇菌株。本研究将专门研究ICR系统，用于将纤维素衍生的原料转化为EtOH，使用可以代谢己糖和戊糖的转基因生物。在用"真实的"纤维素衍生原料测试反应器性能之前，将用简单的糖混合物系统地检查有机抑制剂对体积生产率的影响。将开发反应堆性能的分析模型，以全面了解参数变化的影响。细胞密度将使用E. coliLY 01表达绿色荧光蛋白（GFP）。本研究讨论了连续流发酵罐的设计，这些发酵罐经过优化以处理纤维素乙醇特有的问题：进料中的抑制剂和颗粒物以及CO2通风。更广泛的影响这项研究为社会带来了好处，因为它有可能为从可再生非粮食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，可能有利于发展中的纤维素乙醇工业经济。该项目是至关重要的PI的努力，建立在得克萨斯理工大学化学工程的教育和推广计划，并支持材料和可再生能源研究与化学工程教育的整合。PI和co-PI的团体历来支持涉及高中生和本科生的外联活动，包括妇女和代表性不足的群体的成员。通过荣誉学院的本科研究奖学金计划和德克萨斯理工大学的ConocoPhilips Bridge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。两名参与的研究生将通过德克萨斯理工大学的Murdough工程伦理学中心完成工程伦理学培训。学生将通过研究发酵罐中使用的多孔聚合物获得中子散射和辐射安全方法的培训。结果将通过在国家和国际会议上的演讲以及通过关于纤维素乙醇的教育网页进行传播，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.