Production of poly-hydroxy-butyrate using nitrogen removing methanotrophic mixed culture bioreactor

Methanotrophic biotechnologies for methane mitigation and nitrogen removal are becoming more apparent. However, the sludge produced during these processes is often underutilized and instead can be applied for resources recovery. Fortunately, methanotrophic bacteria can utilize methane while also producing poly-hydroxy-butyrate (PHB), bioplastics, under nutrients deficient conditions. Bioplastics are increasing in popularity and can be produced from unexploited resources, such as methane and carbon dioxide, within wastewater facilities. This research demonstrates that methanotrophic sludge generated during a methanotrophic-based nitrogen removal process, which has been recently suggested, can be directly utilized for PHB production. It was found that the PHB storage response of the methanotrophic driven mixed culture was greatest when methane and oxygen were supplied in equal volume to volume ratios. In addition, the PHB response due to imposing feast-like conditions along with nitrogen or phosphorus deprivation were assessed. The highest PHB storage achieved was 21 ± 1.31% after one cycle under methane sufficient and nitrogen limited conditions. Whereas, only applying feast-like conditions demonstrated a PHB storage of 15 ± 0.67% while simultaneously removing nitrate. Finally, further optimization and continued feast- and famine-like cycles can lead to a greater PHB storage response by the culture. •The methanotrophic culture was enriched in a novel bioreactor for nitrogen removal.•Feast and famine-like conditions were applied based on methane availability.•Achieved a maximum PHB capacity of 21 ± 1.31% in a mixed methanotrophic culture.•Feast and famine conditions and nitrogen limitation led to the greatest capacity.