Upper mesophilic temperature acclimation of halophilic, hydrogen-producing bacteria from salt fields was investigated in this study, along with the changes in microbial abundance during anaerobic digestion (AD) process. Genomic approaches such as PCR-denaturing gradient gel electrophoresis (DGGE) and next-generation sequencing (NGS) were performed to profile the microbial communities. During AD, there was a significant abundance of Halanaerobacter lacunarum at 48°C followed by the increase in hydrogen yield, signifying potential contribution from the halophile in the hydrogen production. A decrease in the dominance of H. lacunarum and Halanaerobium fermentans at 42°C, likely due to an increase in other bacterial species, was noted but their dominance significantly increased at temperatures of 45°C and 48°C. This investigation provides valuable insights in highlighting the potential of Halanaerobium sp. and the other halophilic bacteria to adapt under upper mesophilic temperature conditions and synthesizing hydrogen. The findings in the present study also underscore the importance of optimizing temperature and pH conditions to maximize hydrogen yield during high-salt anaerobic digestion
