Microstructure, bacterial community and metabolic prediction of multi-species biofilms following exposure to di-(2-ethylhexyl) phthalate (DEHP)

Abstract

The occurrence and transportation of phthalate esters in biofilms from natural and engineered sources have attracted considerable research interest. However, little information is available highlighting the responses of multi-species biofilms in terms of their physicochemical structure and bacterial community induced by phthalate esters. Di-(2-ethylhexyl) phthalate (DEHP), a model phthalate eater, was selected to treat multi-species biofilm aggregates, including an attached biofilm from a moving bed bioreactor (MBBR), a periphytic biofilm from a natural source and activated sludge in short-term exposure experiments (120 h). The production of extracellular polymeric substances (EPS) from the three biofilms initially decreased and then slightly increased after exposure to DEHP, consistent with the variation of the most dominant fluorescent compounds consisting of humic-acid-like organic substances. The MBBR and periphytic biofilms secreted more fluorescence compounds than the activated sludge during the exposure period. The organic matter in the EPS was converted into smaller molecules, while limited variation was observed in the functional groups and secondary protein structures. Acinetobacter and Bacillus demonstrated significant increases and were likely the key genera responsible for DEHP degradation. The combined use of spectral, chromatographic and sequencing analyses indicated that the periphytic biofilm was more resistant to DEHP, possibly owing to the presence of more mature assemblages, including cells with higher metabolic activity and a higher diversity within the bacterial community. This study provides insights into the microstructural and bacterial responses of multi-species biofilms following exposure to phthalate esters, and provides important guidance for bioremediation of phthalate esters using periphytic biofilms.

Keywords: Bacterial community; Di-(2-ethylhexyl) phthalate (DEHP); Extracellular polymeric substances (EPS); Moving bed bioreactor (MBBR); Periphytic biofilm.