Halophilic Nitratireductor aquibiodomus NITDSM8 from the Coastal Water of Odisha: A Novel Source for Polyhydroxybutyrate Production, Characterization and RSM-Based Optimization

The escalating environmental impacts of petroleum-based plastics on terrestrial and aquatic ecosystems have intensified the demand for sustainable and biodegradable alternatives, including polyhydroxybutyrate (PHB). In this study, halophilic bacteria were isolated from the coastal waters of Puri, Odisha, an unexplored marine ecosystem that harbours microorganisms that are capable of synthesizing biopolymers. Nitratireductor aquibiodomus NITDSM8 showed the highest level of intracellular PHB accumulation among the isolates. To the best of our knowledge, this study is the first to report PHB synthesizing capability by this species. The structural identification of the recovered polymer was confirmed through its physicochemical properties, which matched those with the commercial PHB. Glucose, peptone, and NaCl were selected as key factors due to their significant effects on biomass synthesis and polymer accumulation. Response Surface Methodology (RSM) resulted in increasing biomass concentration to 4.8 g/L, marking a 1.9-fold improvement. The PHB production process reached a maximum yield of 75.2% (w/w) with a PHB concentration of 3.6 g/L under these optimized conditions. This resulted in a 1.34-fold increase in the PHB yield and approximately a 2.5-fold increase in PHB concentration. The strain showed consistent growth and sustained polymer production in high NaCl concentration, indicating its physiological tolerance for bioprocess applications in higher saline environments. Overall, these findings suggest that N. aquibiodomus NITDSM8 is a promising new halophilic strain for efficient, scalable, and sustainable PHB production.