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.