Sustainable bioplastics production from industrial wastewaters using photosynthetic microbial production of polyhydroxyalkanoates (PHAs)

Plastics, due to their light weight, low cost and ease of processing have become the material of the 21st century, but this tremendous growth has also resulted in many environmental burdens with significant impact on aquatic and bird life through ingestion and entrapment, and long term terrestrial- and bio- accumulation. In recent years bioplastics have been seen as a way to potentially mitigate some of these impacts. This is because bioplastics, in the truest sense of the term, are plastics that are both derived from renewable biomass sources and readily biodegradable, significantly mitigating the impacts associated with conventional petroleum based plastics. In this study we explore the production of polyhydroxyalkanoates (PHAs), a biopolyester thermoplastic produced by bacteria, for simultaneous industrial wastewater treatment and carbon recovery to value added products. Conventionally, PHAs are produced using agricultural feedstocks that are fermented and the fed to pure cultures under a feast-famine (FF) regime. Such processes are commercialized, but market share is limited solely by the higher price of production compared with petro-plastics. Anoxygenic phototrophs are a group of microorganisms that gather energy from the sun, can uptake organic carbon without aeration, and are capable PHA producers. In this project we propose to use nutrient-limited organic-laden petrochemical wastewater and mixed cultures abundant in anoxygenic phototrophs to overcome the three major costs of current production: 1) cost of feedstock; 2) energy used for aeration; and 3) energy used for sterilization. Operational conditions including light wavelength and intensity, light cycling, temperature, substrate components and degree of fermentation, mixing, and pH will be explored to fully understand process parameters on PHA production and refine conditions for scale up design. Concurrently, high-throughput DNA sequencing, flow cytometry, and molecular biology techniques will be used to study microbial community changes and identify key functional organisms and their PHA synthesis genes to further optimize the system. At project completion a small scale outdoor raceway pond system will be prototyped at QAPCO facilities treating QAPCO wastewater under open conditions for PHA production. In parallel, the study will investigate and refine known PHA extraction techniques tailored for the organisms and cell densities resulting from our process for optimized yield, purity and molecular weight integrity. Extracted PHA polymers and co-polymers will be characterized with respect to their chemical composition and thermo-mechanical properties, and subsequently blended with other polymers to achieve desirable properties for commercial application while maintaining biodegradability. Polymer characterization will feedback to culture process operation to achieve conditions where bacteria produce the optimum monomer compositions for polymer blending. To confirm the suitability of the process traditional FF cultures will also be tested on the same wastewater as a benchmark and a life cycle assessment of environmental and economic costs compared to traditional PHA production and petro-plastic production will be conducted. At the end of this project we aim to have developed a refined process for integrated PHA production with petrochemical wastewater management and to have piloted at small scale under environmental conditions. Explicitly, our goal is to employ circular bioeconomy practices to expand QAPCOs existing plastic product lineup and from this project provide the necessary knowledge to move to fully integrated piloting. Such initiatives allow a smooth transition from existing petroleum economy to a knowledge fueled circular economy by leveraging on the former, in line with Qatar National Vision 2030 objectives.

Hamad Bin Khalifa University (HBKU)