Bacterial Diversity and Function of Aerobic Granules Engineered in a Sequencing Batch Reactor for Phenol Degradation

Abstract

Aerobic granules are self-immobilized aggregates of microorganisms and represent a relatively new form of cell immobilization developed for biological wastewater treatment. In this study, both culture-based and cultureindependent techniques were used to investigate the bacterial diversity and function in aerobic phenol-degrading granules cultivated in a sequencing batch reactor. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes demonstrated a major shift in the microbial community as the seed sludge developed into granules. Culture isolation and DGGE assays confirmed the dominance of ␤-Proteobacteria and high-G؉C gram-positive bacteria in the phenol-degrading aerobic granules. Of the 10 phenol-degrading bacterial strains isolated from the granules, strains PG-01, PG-02, and PG-08 possessed 16S rRNA gene sequences that matched the partial sequences of dominant bands in the DGGE fingerprint belonging to the aerobic granules. The numerical dominance of strain PG-01 was confirmed by isolation, DGGE, and in situ hybridization with a strain-specific probe, and key physiological traits possessed by PG-01 that allowed it to outcompete and dominate other microorganisms within the granules were then identified. This strain could be regarded as a functionally dominant strain and may have contributed significantly to phenol degradation in the granules. On the other hand, strain PG-08 had low specific growth rate and low phenol degradation ability but showed a high propensity to autoaggregate. By analyzing the roles played by these two isolates within the aerobic granules, a functional model of the microbial community within the aerobic granules was proposed. This model has important implications for rationalizing the engineering of ecological systems.

Evidence of species succession during chlorobenzene biodegradation

“…One of the published studies describes the characterisation of a phenol degrading community present in aerobic granules, where the dominant degrader in the bioreactor was found to be a Pandoraea spp. Similarly to our study, this strain emerged as the fastest degrader and was stably maintained over the operating period (Jiang et al, 2004). Other studies also reported the degradation of aromatic compounds, such as p-xylene, 1,3-dihydroxybenzene and 2-chlorobenzoate (Bramucci et al, 2002;Demnerova et al, 2003;Matsui et al, 2006).…”

Microbial community analysis for aerobic granular sludge reactor treating high-level 4-chloroaniline wastewater

“…The homology between band 11 and Anoxynatronum sibiricum was 88.1 %, whereas the homology between band 12 and Xanthomonas sp. PG-07 (Jiang et al 2004) and Xanthomonas axonopodis (Malik et al 2003) was 99.0 %. Furthermore, the homology between band 5 and the uncultured Cytophagales OPB56 was 90.6 %, and the homology between band 6 and the uncultured Planctomycete Clone T-RF20-23 was 90.4 %.…”

Degradation of phenol by aerobic granules and isolated yeast Candida tropicalis

“…One likely reason accounting for the high degradation efficiency of granules that degrade phenol is the mass transfer barrier provided by a granule matrix that produces lower local phenol concentrations on cells than the bulk value (Liu and Tay, 2004). Jiang et al (2004b) isolated 10 bacterial strains from their aerobic phenol-degrading granules and identified their potential for degrading phenol. The PG-01 strain, a member of b-proteobacteria, is common in granules and is the predominant strain in phenol degradation.…”