Metabolic Flexibility of Ammonia Oxidizing Bacteria in a Coupled Nitrification-Biomethanol Production Process

Biological methanol production using ammonia-oxidizing bacteria offers an attractive and efficient alternative for carbonaceous recovery from wastewater. In this study, we explore the impacts of CH4 exposure and co-oxidation on the community structure, function, and adaptation of a mixed microbial culture of nitrifying bacteria. The transition to a NH3 and CH4 cofeeding regime in a continuous flow bioreactor resulted in high-efficiency ammonia conversion (>90%) concurrent with CH3OH production. CH4 exposure also led to the selective out-competition of nitrite-oxidizing bacteria as well as the development of a modified nitrifying consortium with higher specific ammonia and nitrite oxidation rates and lower biomass yield coefficients. Metabolic flexibility of AOB during NH3–CH4 cometabolism was reflected in gene expression profiles favoring anabolism (cbbL) over catabolism (amoA, hao). However, the functional biomarker in AOB most impacted by NH3–CH4 co-oxidation corresponded to electron flow (nirK). In summary, we demonstrate the feasibility of a versatile biotechnological platform aimed at concurrent nitrification and biomethanol production. Upon further optimization, such integrated platforms could harness the potential of microbial communities to fulfill multiple interlinked objectives within a resource-efficiency framework.