A newly isolated halotolerant Rubrivivax gelatinosus MBE with capable of producing hydrogen in the presence of ammonium

The large-scale cultivation of photosynthetic bacteria requires significant quantities of fresh water. Screening strains that can thrive in brackish water or seawater is a solution to mitigate the dwindling availability of freshwater. Through phylogenetic analysis based on 16S rDNA sequences, this study identified a strain Rubrivivax gelatinosus MBE isolated from seawater. The effects of several key factors, including carbon sources, pH, NH₄⁺ and NaCl concentration on hydrogen production performance were investigated. Rubrivivax gelatinosus MBE showed a preference for glucose, but not organic acids for hydrogen production. It also exhibited alkalinity, achieving its peak hydrogen yield of 4626.82 ± 155.65 mL⋅L⁻¹ at pH 8. Interestingly, Rubrivivax gelatinosus MBE could exploit ammonium nitrogen for hydrogen synthesis, thriving even in specific ammonium and salt concentrations. Its resilience was further highlighted by a maximum hydrogen production yield of 4741.41 ± 167.01 mL⋅L⁻¹ and a hydrogen production rate of 37.59 ± 3.37 mL⋅L⁻¹⋅h⁻¹ with 10 g⋅L⁻¹ NaCl, underscoring its significant salt tolerance. These results suggested that Rubrivivax gelatinosus MBE could be a promising candidate for biofuel production, and it is significant to take sustainability study on the application of MBE to deal with alkali wastewater from paper making, pharmacy and printing and high salinity wastewater in the future.