Conversion of waste gases into sustainable animal feeds using mixotrophic bacteria

Industrial processes such as fuel refining and waste treatment produce large quantities of mixed waste gases. A sustainable and lucrative solution is to use gas-consuming bacteria to convert these gases into nutritionally rich animal feeds. While previous work has shown chemoautotrophs can convert single gaseous substrates, mixed gas conversion remains unexplored. Here we will validate and optimise the ability of chemoautotrophs, i.e. bacteria that grow using gases as their energy and carbon sources, to microaerobically convert mixed waste gases into commercial feeds. Our central innovation, based on our previous high-profile research demonstrating unexpected metabolic flexibility of bacteria, is that process efficiency and stability can be enhanced by using mixed rather than single gaseous substrates. First, we will compare the performance of four bacterial strains using different mixed gas combinations by using different proportions of CO2, H2, CH4, CO, and H2S as energy/carbon sources. We will then use genetic engineering to enhance product value and experimental evolution to optimise process efficiency of the two most promising strains. Finally, we will scale-up production using batch and continuous bioreactors. The aim is to produce high-yield protein feeds suitable for pets, livestock, and aquaculture, as well as higher-value genetically engineered fish feeds containing carotenoids and omega-3 fatty acids. A positive outcome could radically enhance the efficiency of chemoautotrophic bioprocesses and be attractive to the rapidly growing gas-to-liquids industry.