Enhanced biodegradation of Baolixile coal by Bacillus sp. XK1 using combined surfactants to produce chain alkanes

The biodegradation of coal is an effective way of clean and efficient utilization of coal. However, how to improve the degradation rate has been the focus of attention. The effect of combined surfactants Tr-Rh (Tr-octyl phenoxy poly ethoxy, Rh-rhamnolipid) on the degradation of Baolixile coal by Bacillus sp. XK1 was studied. The degradation experiment showed that compared with non-surfactant, the degradation rate of Tr-Rh increased by 25.4 % and the degradation time was shortened by 2 days. The bacterial growth characteristics experiment found that in the presence of Tr-Rh, the highest OD 600 of Bacillus sp. XK1 reached 1.311 and the alkaline protease activity was 93.09 U/mL, indicating that Tr-Rh promoted the growth of Bacillus sp. XK1 , secreting more alkaline proteases, and increasing the contact with coal. The surface property experiments of coal showed that, the contact angle and adsorption rate of coal sample were 16.2 ° and 68.3 % in the presence of Tr-Rh respectively, which indicated that Tr-Rh improved the hydrophilicity and charge of coal surface, and increased the adsorption of bacteria on the coal surface. Furthermore, the degradation products were characterized by GC–MS and FTIR. Compared with non-surfactant, the chain alkanes of the liquid bioproducts increased from 48.22 % to 66.10 % in the presence of Tr-Rh. FITR analysis indicated that Bacillus sp. XK1 , in the presence of Tr-Rh, degraded certain aromatic rings and side-chain groups in coal samples. This study provides a new method and theoretical basis for the efficient biodegradation of coal by microorganisms to produce chain alkanes.