Membrane Bioreactors for the Production of Bio-polymers from Industrial Waste Streams

由于各种原因，包括对可再生和可生物降解化学品的需求，农村经济发展，环境可持续性和废物管理，生物塑料生产取代石化基聚合物正在成为一个重要的研究和商业领域。加拿大有丰富的工业和农业废物流富含碳，这是生物聚合物合成的主要原料目标。聚羟基链烷酸酯（PHA）是一组可以通过细菌发酵生产的聚合物，具有工业和商业价值，因为它们可以取代化石燃料基聚酯，并且是可生物降解的。PHA的亚组，具有6-14个碳链长度的那些被称为中链长度PHA（mcl-PHA），由于其有利的热塑性性质而具有高的商业价值。影响PHA生产的总体经济性的最重要因素是PHA生产率（所生产的PHA质量/反应器体积/时间）和原料成本。这项研究旨在这两个方面取得重大进展。纯化学原料将被马铃薯加工厂（废油）和生物柴油生产厂（废甘油）的工业废物流所取代。我们将探索细菌发酵方法，以最大限度地从这些废物来源生产mcl-PHA。我们将确定生产的PHA的浓度和组成，并评估其潜在的商业价值。我们将进行分批发酵实验，以评估最佳的碳负荷，培养基条件，并需要原料灭菌生产mcl-PHA。我们将确定生产的PHA的浓度和组成，并评估最大产量和生产力的条件。当从分批或半分批进料操作切换到连续进料操作时，PHA的体积生产率可以显著增加。我们将使用膜生物反应器（MBR）系统进行连续进料发酵，以提高容积生产率，减少生产占地面积，提供一致的产品质量，并减少生产停机时间。这将标志着MBR系统（通常用于废水处理）首次被评估用于从工业废水流中生产mcl-PHA。先前在分批进料条件下建立的碳负荷、培养基组成和无菌要求将形成连续进料模式下MBR研究的初始基础。稀释率、营养成分和固体保留时间将在MBR系统中通过实验改变，以建立高PHA生产率和产量的条件。将根据污染速率和强度以及清洁频率和膜寿命评估膜过滤性能。增加的体积生产率、更小的工厂占地面积、更一致的产品质量和更少的停机时间可以大大降低生产成本并提高生物聚合物生产的整体可行性。这项研究将支持加拿大日益增长的生物精炼工业，进一步发展现有的科学知识基础，并为工业应用提供新的替代生产系统。加拿大的生物加工和环境部门预计将扩大，再加上这些部门的退休人员增加，对训练有素和合格人员的需求将是巨大的。超过三分之一的生物技术部门的公司报告说，劳动力和技能短缺。这项研究将为这些不断发展的领域的研究生和本科生工程专业学生提供良好的培训，使区域和国家的相关行业受益。

Bio-plastics production to displace petrochemical based polymers is emerging as an important research and commercial area due to a variety of reasons including the need for renewable and biodegradable chemicals, rural economic development, environmental sustainability, and waste management. Canada has abundant industrial and agricultural waste streams rich in carbon, which are prime feedstock targets for bio-polymer synthesis. Polyhydroxyalkanoates (PHAs) are a group of polymers that can be produced through bacterial fermentation and are of industrial and commercial interest, as they can replace fossil-fuel based polyesters and are biodegradable. A sub-group of PHAs, those with carbon chain lengths of 6-14 termed medium chain length PHAs (mcl-PHAs) have a high commercial value due to their favorable thermoplastic properties. The most important factors affecting the overall economics of PHA production are PHA productivity (mass of PHA produced/reactor volume/time) and cost of raw materials. This research aims to make significant progress on both these fronts. Pure chemical feedstock will be replaced by industrial waste streams from potato processing (waste oils) and biodiesel production (waste glycerol) plants. We will explore bacterial fermentation methods to maximize the production of mcl-PHAs from these waste sources. We will determine the concentration and composition of the PHAs produced and assess its potential commercial value. We will carry out batch fermentation experiments to assess optimum carbon loading, media conditions, and need for feedstock sterilization for the production of mcl-PHAs. We will determine the concentration and composition of the PHAs produced and assess the conditions for maximum yield and productivity. The volumetric productivity of PHAs can be increased substantially when switching from a batch or semi-batch feed operation to a continuous-feed operation. We will use a Membrane Bioreactor (MBR) system for continuous-feed fermentation to increase volumetric productivity, decrease production footprint, provide consistent product quality, and reduce production down-time. This will mark the first time MBR systems (commonly used for waste water treatment) will be evaluated for the production of mcl-PHAs from industrial waste streams. Carbon loading, media composition, and sterility requirements previously established in batch-feed conditions will form the initial basis for MBR studies in continuous-feed mode. Dilution rates, nutrient composition, and solid retention times will be varied experimentally in the MBR systems to establish conditions of high PHA productivity and yield. Membrane filtration performance will be assessed based on fouling rate and intensity as well as cleaning frequency and membrane life. Increased volumetric productivity, smaller plant footprint, more consistent product quality, and less operating downtime could substantially reduce production cost and improve overall viability of biopolymer production. This research will support the growing bio-refining industry in Canada, furthering the existing scientific knowledge base and providing a new alternative production system for industrial application. The bio-processing and environmental sector in Canada is projected to expand, and coupled with increased retirements from these sectors, the need for highly trained and qualified people will be substantial. More than one third of the companies in the biotechnology sector have reported labour and skill set shortages. This research will provide excellent training to graduate and undergraduate engineering students in these growing fields, benefiting related industries both regionally and nationally.