Optimization of Methane Feed and N:C Ratio for Biomass and Polyhydroxybutyrate Production by the Alphaproteobacterial Methanotroph Methylocystis sp. Rockwell

The consumption of methane and the production biodegradable polymers using alphaproteobacterial methanotrophs offers a promising strategy to mitigate greenhouse gas emissions reduce non-biodegradable plastic pollution. This study identified an ideal amount added N:C ratio in 100 mL batch cultures methanotroph Methylocystis sp. Rockwell growing 1-L sealed bottles Response Surface Methodology (RSM) achieve both high biomass polyhydroxybutyrate (PHB) production. RSM analysis showed achievement optimal at 474.7 ± 10.1 mg/L nitrate mineral salts (NMS) medium 480.0 65.5 ammonium (AMS) with 8 mmol 0.022. However, PHB concentration was achieved 6 ratios 0.012 NMS (149.7 16.1 mg/L) 0.022 AMS (200.3 5.1 mg/L). A multi-objective projected maxima %PHB cell content (based on dry weight) when 4.88 0.016 cultures, 6.28 cultures. Cultures grown under these conditions produced 173.7 mg PHB/L 46.8% 196.9 53.1% AMS. Taken together, analyses predicted for growth confirmed preference as N-source information is valuable media formulation industrial scale-up