Glycine betaine enhances biodegradation of phenol in high saline environments by the halophilic strain Oceanobacillus sp. PT-20

The halophilic bacterial strain PT-20, isolated from saline alkali soil samples and identified as a member of the genus Oceanobacillus, exhibited a robust ability to degrade phenol under high salt conditions. It was determined that strain PT-20 was capable of degrading 1000 mg L−1 phenol completely in the presence of 10% NaCl within 120 h. Under the optimal degradation conditions, pH 8.0, 3% NaCl and 30 °C, 1000 mg L−1 phenol could be completely degraded in 48 h. Interestingly, the biodegradation rate of phenol was dramatically improved in the presence of glycine betaine. When glycine betaine was added, the time required to degrade 1000 mg L−1 phenol completely was significantly reduced from 120 h to 72 h, and the corresponding average degradation rate increased from 8.43 to 14.28 mg L−1 h−1 with 10% NaCl. Furthermore, transcriptome analysis was performed to investigate the effects of phenol and glycine betaine on the transcriptional levels of strain PT-20. The results indicated that the addition of glycine betaine enhanced the resistance of cells to phenol, increased the growth rate of strain PT-20 and upregulated the expression of related enzyme genes. In addition, the results of enzyme activity assays indicated that strain PT-20 degraded phenol mainly through a meta-fission pathway.