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

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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.