From wetlands to wastewater: leveraging natural biomes to determine key factors for engineering stable biological processes

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Waste management and renewable energy represent critical challenges for sustainability and emissions reduction in Canada. The process of anaerobic digestion (AD) addresses both of these needs through the combined activities of bacteria and other microbes in the break down of waste into biogas (methane and carbon dioxide) for energy. Currently Canada accesses only 13% of its potential biogas production via AD. Wider application of AD is limited in part because of the inconsistency in methane (the portion of biogas used for energy) yield. The instability of the interactions between the microbes within AD systems when exposed to disruptions in conditions and toxins is a key factor in methane yield. An emerging strategy in waste management is the reduction of waste volume by hydrothermal liquefaction (HTL) of wet waste for production of biocrude fuel. Liquid by-products of HTL contain many compounds known to boost methane production in AD, namely volatile fatty acids. However, HTL by-products also contain many toxins which are not tolerated by the microbes in most AD systems, and disrupt the stability of the system, reducing overall methane yield. Valorization of HTL by-products is critical for the economic viability of biocrude production by HTL, just as greater stability of microbial systems is needed for wider implementation of AD. Wetlands are a natural analogue for AD processes, and are among the highest methane producing environments on the planet. Water from streams and rivers collect in wetlands, often causing the build-up of toxic compounds. As such, wetlands and may contain microbes with a high potential to tolerate these toxins. While sourcing natural microbial communities to supply stability to engineered systems is growing in use, the mechanisms of this stability remain unresolved if this approach is to be implemented at scale in engineered microbial processes. This Discovery Grant aims to build a path toward wider use of AD and HTL technologies by addressing specific factors underlying the stability of engineered microbial systems. This will be achieved through construction and study of a model microbial system with microbes from wetland sediments to test three specific factors that contribute the stability of microbial interactions: 1) The metabolic capacity to tolerate various toxic compounds, 2) Microdiversity: small genetic variation within microbial species that may allow for survival in changing conditions 3) Presence of phage: viruses that infect and kill specific microbes. In developing a process to select for microbes from wetland that tolerate toxins, we are constructing a model system that can be used to test the specific factors underlying stability of AD processes. This approach will provide both fundamental and applied knowledge while training students and researchers in the rapidly growing area of engineered microbial systems.