Effects of regular addition and discontinuation of biosurfactant on hydrocarbon biodegradation and microorganisms in heavy oily sludge

Purpose This study was conducted to investigate the effect of biosurfactant and nutrient amendment on the bioremediation of heavy oily sludge. The biosurfactants exhibit characteristics of amphiphilicity, emulsifying activity, and biodegradability. The application of biosurfactant, appropriate water and nutrition, combined with mechanical stirring effectively enhanced bioremediation, providing a promising scheme for sustainable development of the ecosystem. Methods Here, biosurfactant was produced by strain Pseudomonas sp. CH1. Biosurfactant (80 mg L −1 ) was periodically added to heavy oily sludge for 10 weeks. The effects of biosurfactants on petroleum hydrocarbon content, catalase activity, and microbial community composition were characterized. Results Compared with the control (water addition only), treatment supplemented with biosurfactants exhibited better performance in degrading total petroleum hydrocarbons and n -alkanes, while regular cumulative addition of biosurfactants inhibited biodegradation. Moreover, the analysis of microbial community structure showed that the biosurfactant selectively enriched microorganisms that are capable of degrading petroleum hydrocarbons. Conclusion The results demonstrate the potential of biosurfactants for heavy oily sludge bioremediation. The application of biosurfactants can improve catalase activity and enrich the degrading populations, thereby promoting the biodegradation of total petroleum hydrocarbons, especially the aliphatic fractions, whereas high biosurfactant content inhibited the biodegradation. Graphical abstract