Acetotrophic Sulphate-Reducing Bacteria (ASRB) were enriched in a sulphidogenic Continuous Stirred Tank Reactor (CSTR) fed with acetate/ethanol and diagnosed by Single-Strand Conformation Polymorphism (SSCP) and 16S rRNA gene clone library. The CSTR was run for 65 days with synthetic wastewater containing sulphate and acetate with intermittent ethanol at hydraulic retention time of 10 h. The Sulphate-Removal Rate (SRR) reached to 3.8 g/(L?day) after 35 days of start-up. The SSCP profiles of bacterial community changed rapidly at the beginning of start-up before Desulphococcus sp., Desulphomicrobium sp., Aminomonas and Anaerolinea formed a stable community. Bacterial diversity decreased when the ethanol in the influent was replaced by acetate of equal Chemical Oxygen Demand (COD). Desulphomicrobium sp. was enriched and found to have a significant role in acetate utilisation. When ethanol was re-added instead of acetate of equal COD strength, microbial diversity increased and the Desulphomicrobium band of SSCP profiles became weak. At the later start-up stage, the 16S rRNA gene clone library indicated the presence of bacteria belonging to six different known phyla and sequences with similarities to those of sulphate-reducing bacteria accounted for 22%. The SSCP band sequences revealed that the characteristics of bacterial community populations resembled those of clone library sequences. The present study showed the addition of ethanol to influent would enhance bacterial diversity and SRR, ASRB could be enriched and Desulphomicrobium sp. was the primary source of acetate oxidation.
Keywords: acetate, ethanol, sulphate-reducing bacteria, SRB, bacterial community structure, single-strand conformation polymorphism, SSCP, bioreactors, synthetic wastewater