Dynamic response of biofilm microbial ecology to para-chloronitrobenzene biodegradation in a hydrogen-based, denitrifying and sulfate-reducing membrane biofilm reactor

Abstract

The dynamic response of biofilm microbial ecology to para-chloronitrobenzene (p-CNB) biodegradation was systematically evaluated according to the composition and loading of electron acceptors and H2 availability (controlled by H2 pressure) in a hydrogen-based, denitrifying and sulfate-reducing membrane biofilm reactor (MBfR). To accomplish this, a laboratory-scale MBfR was set up and operated with different influent p-CNB concentrations (0, 2, and 5 mg p-CNB/L) and H2 pressures (0.04 and 0.05 MPa). Polymerase chain reaction-denaturing gel electrophoresis (PCR-DGGE) and cloning were then applied to investigate the bacterial diversity response of biofilm during p-CNB biodegradation. The results showed that denitrification and sulfate reduction largely controlled the total demand for H2. Additionally, the DGGE fingerprint demonstrated that the addition of p-CNB, which acted as an electron acceptor, was a critical factor in the dynamics of the MBfR biofilm microbial ecology. The presence of p-CNB also had a more advantageous effect on the biofilm microbial community. Additionally, clone library analysis showed that Proteobacteria (especially beta- and gamma-) comprised the majority of the microbial biofilm response to p-CNB biodegradation, and that Pseudomonas sp. (Gammaproteobacteria) played a significant role in the biotransformation of p-CNB to aniline.