Governments and private enterprises alike are gearing up for travel across our Solar System. Plans to colonize nearby planets are underway, with Elon Musk spearheading the initiative to put a human colony on Mars by 2030. In a parallel vein, NASA is planning a manned exploratory mission to Mars as early as the 2030s. Several other space agencies have similar plans and timelines for their own Mars explorations. This exciting time in our history nonetheless comes with the challenges of long-term space travel. Two ecological and economic challenges arise: the sustainable management of waste produced on a spaceship and the high cost of shipping materials to space.
This year, the University of Calgary's project involves using genetically engineered E. coli to turn human waste into bioplastics. We envision our project as a start-to-finish integrated system that can be used in space to generate items useful to astronauts during early Mars missions. This will solve the problem of waste management by upcycling solid human waste into a usable product. It will also reduce astronautical costs, as expensive fuel routinely used to ship materials to space can be saved.
Poly(3-hydroxybutyrate) (PHB) is a linear polyester and is a product of bacterial fermentation of some sugars or lipids (Anjum, 2016). PHB is used by bacteria (such as Ralstonia eutropha and Pseudomonas aeruginosa) (Anderson, 1990) as carbon and energy storage (Tsuge, 2003). PHB is one preferred alternative to petroleum-based plastics due to its biodegradability (Tsuge, 2003) and the potential for more environmentally friendly manufacturing processes. Current PHB production processes are costly, which limits industrial scale use and application of PHB (Anjum, 2016). We aim to eliminate the cost of using lipid or sugar feedstocks in PHB-production facilities by using human solid waste as a feedstock. We have engineered recombinant Escherichia coli to utilize genes from native PHB-producing bacteria. These genes code for enzymes in the glycolysis and fatty acid beta-oxidation pathways (which break down sugars and lipids, respectively), and in PHB production. We thus hope to optimize PHB production by improving yields and cutting costs, which would promote the use of PHB in industry. This process could also improve the management of human waste by producing a value-added product.
We have focused our efforts on PHB synthesis in engineered E. coli cells, PHB secretion from these cells for easy harvest, the overall start-to-finish process development, and how our project will impact the future of space travel through our human practices work.
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Anderson, A. & Dawes, E. (1990). Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates. Microbiol Rev., 54(4): 450-472
Anjum, A., Zuber, M., Zia, K.M., Noreen, A., Anjum, M.N. & Tabassum, S. (2016). Microbial production of polyhydroxyalkanoates (PHAs) and its copolymers: A review of recent advancements. Int J Biol Macromol., 89: 161-74
Tsuge, T., Taguchi, K., Seiichi, T. & Doi, Y. (2003). Molecular characterization and properties of (R)-specific enoyl-CoA hydratases from Pseudomonas aeruginosa: metabolic tools for synthesis of polyhydroxyalkanoates via fatty acid ß-oxidation. Int J of Biol Macromol., 31(4–5): 195–205