Biodegradations of three different rank coals by a newly isolated bacterium Bacillus sp. XK1

Abstract

Biodegradation of coal was closely related to coal rank. In this study, three kinds of coals whose coal ranks from high to low were Zhundong coal (ZDC), Hongshaquan coal (HSQC) and Heishan coal (HSC) were degraded by Bacillus sp. XK1 isolated from mine water. The degradation experiment results indicated that the degradation rate increased with the decrease of coal rank, and the highest degradation rate of HSC (low-rank coal) was 78.2 %, which was three times higher than that of ZDC (high-rank coal). The enzyme activity experiment showed that the alkaline protease and lignin peroxidase secreted by Bacillus sp. XK1 were key substances for coal biodegradation, and the alkaline protease activity and lignin peroxidase activity were all the highest in the presence of HSC, which were beneficial for coal biodegradation. The adsorption experiment found that HSC was more favorable to contact with Bacillus sp. XK1 than ZDC and HSQC. Furthermore, biodegradation products analysis suggested that with the decrease of coal rank, the contents of long chain alkanes in liquid products increased, among which the highest content of long chain alkane in liquid product of HSC was 86.98 %. The above experimental results demonstrated that biodegradation of low rank coal was an effective pathway.