Analyses of community structure and role of immobilized bacteria system in the bioremediation process of diesel pollution seawater

Immobilized bacteria system plays an important role during degradation process in oil contaminated seawater. Although the immobilized bacteria system can be recycled to avoid pollution after remediation, it remains an open question on whether or not the secondary pollution occurs during the degradation process. Additionally, the research on the role of immobilized bacteria system in the process of oil removal is not clear enough. In this study, both the diesel degradation rate of diesel by immobilized bacteria system and changes in marine microbial community structure were determined to explore the role of immobilized bacteria system. The immobilized bacteria system was added to the diesel polluted seawater (1% diesel) for 30 days. The degradation performance was investigated during the process, and the microbial community structure was analyzed simultaneously. The results illustrated that the degradation rate of diesel by immobilized bacteria system reached 78.39% after 30 days, and Alcanivorax (59.09%), Achromobacter (24.34%) and Thalassospira (9.84%) were the dominant genera in the immobilized bacteria system. The addition of immobilized bacteria system increased the content of nitrogen and phosphorus, and then promoted the growth of oil-degrading bacteria. Thus, functional genes related to oil degradation increased. Additionally, there was little difference in the microbial composition between the treated seawater and the unpolluted seawater. Based on all results, it can be inferred that immobilized bacteria system triggered and stimulated diesel degradation process. This study provides a promising way to improve the removal of oil, and provides theoretical support for the wide application of immobilized microorganism technology.