Investigation into the causes for the changed biodegradation process of dissolved pyrene after addition of hydroxypropyl-β-cyclodextrin (HPCD)

► The initial concentration of pyrene for biodegradation was kept under its apparent solubility. ► Biodegradation process of originally existing states of pyrene was monitored using synchronous fluorimetry non-destructively. ► Possible reasons for the influence of HPCD's addition on biodegradation process of pyrene were investigated. ► Hydrophobicity and emulsifying activity of microorganisms were found to be important factors influence biodegradation of pyrene. Bioremediation of surface waters contaminated with polycyclic aromatic hydrocarbons (PAHs) is a serious problem, often limited by the low bioavailability of contaminants as a result of their low aqueous solubility. In this study, we studied the influence of hydroxypropyl-β-cyclodextrin (HPCD) addition on the biodegradation of dissolved pyrene in aqueous solution. Five types of unidentified bacterial strains were used with a concentration of pyrene under its solubility limit. The reduction of pyrene content was monitored during the biodegradation process using synchronous fluorimetry. The presence of HPCD changed the rate of pyrene biodegradation by microorganisms due to the formation of an inclusion complex between pyrene and HPCD. The hydrophobicity and the emulsifying activity of microorganisms relative to their biodegrading capacity were investigated. The results indicated that hydrophobicity and emulsifying activity of the microorganisms were important factors that can influence the biodegradation process. The hydrophobicity and emulsifying activity were strongly correlated with the biodegrading capacity of the microorganisms toward pyrene in the presence of solubilizing agents or organized media.