Effects of electrochemical reduction reactions on the biodegradation of recalcitrant organic compounds (ROCs) and bacterial community diversity.

Five bacterial species, capable of degrading the recalcitrant organic compounds (ROCs) diethyleneglycol monomethylether (DGMME), 1-amino-2-propanol (APOL), 1-methyl-2- pyrrolidinone (NMP), diethyleneglycol monoethylether (DGMEE), tetraethyleneglycol (TEG), and tetrahydrothiophene 1,1-dioxide (sulfolane), were isolated from an enrichment culture. Cupriavidus sp. catabolized 93.5+/-1.7 mg/l of TEG, 99.3+/-1.2 mg/l of DGMME, 96.1+/-1.6mg/l of APOL, and 99.5+/-0.5mg/l of NMP in 3 days. Acineobacter sp. catabolized 100 mg/l of DGMME, 99.9+/-0.1 mg/l of NMP, and 100 mg/l of DGMEE in 3 days. Pseudomonas sp.3 catabolized 95.7+/-1.2 mg/l of APOL and 99.8+/-0.3 mg/l of NMP. Paracoccus sp. catabolized 98.3+/-0.6 mg/l of DGMME and 98.3+/-1.0 mg/l of DGMEE in 3 days. A maximum 43+/-2.0 mg/l of sulfolane was catabolized by Paracoccus sp. in 3 days. When a mixed culture composed of the five bacterial species was applied to real wastewater containing DGMME, APOL, NMP, DGMEE, or TEG, 92~99% of each individual ROC was catabolized within 3 days. However, at least 9 days were required for the complete mineralization of sulfolane. Bacterial community diversity, analyzed on the basis of the TGGE pattern of 16S rDNA extracted from viable cells, was found to be significantly reduced in a conventional bioreactor after 6 days of incubation. However, biodiversity was maintained after 12 days of incubation in an electrochemical bioreactor. In conclusion, the electrochemical reduction reaction enhanced the diversity of the bacterial community and actively catabolized sulfolane.