Characterization of the action of different hydrolytic bacteria and compound bacterial agents on long-flame coal

The process of coal-to-biogas mainly relies on the joint action of bacteria and archaea,gas production is the purpose,and the substrate utilization of coal is the key. The hydrolysis is the rate-limiting step of the whole fermentation process,which is related to the hydrolysis rate and degradation rate of coal. Hydrolysis bacteria,as an important functional group of coal-to-methane anaerobic fermentation process,are of special importance for studying the characteristic degradation function of the dominant hydrolysis strains. In this study,the degradation characteristics of coal were analyzed by each single strain and compound bacterial agent with the bacteria in the hydrolysis process, and the conjugation relationship between the strains was explored. The results were as follows:the sample after combined degradation of Bacillus immobilis and Pseudomonas aeruginosa in gas production showed the highest total gas production,with the total gas production of 19.86 mL/g. The sample after Pseudomonas treatment showed the highest total methane production, with the total methane production of 10. 78 mL/g. The degradation characteristics of the combined degradation of Bacillus immobilis and Pseudomonas were similar to those of Bacillus immobilis. The combined degradation of Bacillus immobilis and Bacillus polymyxa lost the degradation ability of OH bond and single-neighboring aromatic C-H bond in the carboxylic acid. The combined degradation of Pseudomonas and Bacillus polymyxa weakened the degradation ability of OH bond and single-neighboring aromatic C-H bond in the carboxylic acid. The specific surface area and the total pore volume of the coal samples degraded by Pseudomonas decreased the most,which decreased by 16.478 m²/g and 0.284 m³/g,respectively. The average pore size of mesopores and macropores generally increased after being degraded by different bacterial agents,while the most pore size of micropores generally decreased. This study provides some references for the improvement of the hydrolysis rate and the final methane production capacity of coal.