Microbial H2 for biocompatible metabolite hydrogenation in vivo Mirren White , Dr Stephen Wallace University of Edinburgh, UK Hydrogenation is one of the most ubiquitous industrial processes worldwide due to its high efficiency and lack of product specificity; any number of carbon-carbon double bonds in any molecule can be reduced in a single reaction. However, the majority of H2 gas is currently manufactured via steam reforming of natural gas, which is a non-renewable resource and requires large amounts of energy. However, hydrogen gas is also a natural metabolite produced by many microbes as a product of anaerobic fermentation. Despite the prevalence of hydrogen in nature, a wealth of understanding surrounding its biosynthesis, and the tools to encode its synthesis into a laboratory microbe, the use of microbial hydrogen gas for hydrogenation chemistry has been limited. Seminal work by Balskus et al has previously shown that an engineered E. coli strain in conjunction with a heterogeneous Pd catalyst can reduce activated alkenes with high efficiency. Here we disclose that, in addition to engineered strains, unmodified laboratory strains of E. coli can be used as a source of H2 gas for biocompatible chemistry when cultured under anaerobic fermentation conditions. Like the engineered strain, the reduction reaction proceeds with high efficiency at ambient temperatures and pressures, achieving a 75-100% reduction of substrates in a similar time frame. Furthermore, this pathway can be used in conjunction with metabolic engineering to reduce metabolites to their saturated forms, as well as to reduce exogenous substrates. Overall, this research suggests a general approach to the bio-production of saturated small molecules, especially those that cannot be accessed via synthetic biology due to the absence of known enzymes. In conjunction with the use of waste feedstocks, this project will provide a sustainable method of manufacture for these difficult-to- access compounds.
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