Study on improving the hydrophilicity of coal by a biosurfactant-producing strain screened from coal

In order to improve the hydrophilicity of coal and solve the potential environmental problems caused by chemical surfactants, in this study, a biosurfactant-producing bacteria (PLD01) was screened from coal through biochemical test screen. The species, biosurfactant types and composition analysis of the strain were studied. PLD01 was identified by 16S rRNA, and exhibited 99% sequence similarity with Pseudomonas bacteria. Fourier Transform Infrared Spectrophotometer (FTIR) analysis showed the presence of N-H, carboxyl groups, and glycosidic bonds in biosurfactants, which were determined as glycolipids. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis showed that the biosurfactants had Mono-rhamno-mono-lipidic congeners (Rha-C12), Di-rhamno-mono-lipidic congeners (Rha-Rha-C10), and Mono-rhamno-di-lipidic congeners (Rha-C12-C10/Rha-C10-C12). Finally, the analysis of the potential and performance of PLD01 to produce surfactants revealed that it was an effective biosurfactant. The yield of biosurfactant was 4.35 g/L when OD600 = 1.34 and cultured for 7 d. The critical micelle concentration (CMC) of the separated biosurfactant was as low as 50.0 mg/L, which reduced the surface tension of water from 72.8 mN/m to 40.6 mN/m. The modified wetting effect was better than the common chemical surfactant sodium dodecyl sulfate (SDS). Therefore, the biosurfactant-producing bacteria have good engineering application prospects.