Anaerobic co-digestion of commercial laundry wastewater and domestic sewage in EGSG pilot scale reactor: influence of surfactant concentration on microbial diversity, evaluation of microbial stratification and bamA gene for anaerobic ring fission

Different molecular tools (PCR-DGGE, high-throughput sequencing of 16S rRNA gene and sequencing of bamA gene) were used to compare and assess the microbial diversity of an EGSB reactor in full scale applied to anaerobic co-digestion of commercial laundry wastewater and domestic sewage submitted to increasing concentrations of anionic surfactant. Using the PCR-DGGE observed a microbial stratification along the sludge blanket of the reactor and, probably, related to size granule. 16S rRNA gene sequencing showed high diversity and richness of the samples, and the lowest Shannon value was obtained for the higher concentration of surfactant. For the Bacteria domain the genera Bellilinea, Syntrophus, Syntrophohobacter, Cytophaga, Bacteroides and Synergistes was the most abundant; whereas for Archaea domain the genera were Methanosaeta and Methanolinea. Only Pseudomonas genus is related to all stages of degradation and unique in the O oxidation. In the other stages, a greater richness (> 6 different genera) was observed, indicating the need for a microbial syntrophism for complete LAS mineralization. In addition, bamA gene sequencing indicated the presence of Syntrophorhabdus aromaticivorans, Desulfosarcine ketonica and Syntrophus aciditrophicus with genetic potential for the aromatic ring cleavage under anaerobic conditions. Therefore, the enrichment and maintenance of these microorganisms are desirable for the bioprocess.