Anaerobe isolation from denitrifying benzene-degrading enrichment culture and their capacity to mineralize benzene

Abstract

AbstractOnly a few benzene-mineralizing anaerobes have been isolated to date. In an attempt using classical isolation techniques to isolate benzene-mineralizing pure cultures from a benzene-mineralizing nitrate-reducing microbial community, two putative isolates were gained under nitrate-reducing conditions spiked separately with acetate and benzene as sole sources of carbon and energy with media containing ammonium or without ammonium. Both putative isolates; Bz4 (with ammonium) and Bz7 (without ammonium) - mineralized13C-labelled acetate under anoxic conditions at 3.3 and 2.7 μM day-1, respectively, revealed by analysis of evolved13CO2. However, only Bz4 mineralized [13C6]-labelled benzene (0.298 μM benzene mineralized day-1) generated up to 960.2 ± 0.3 ‰ δ13C-CO2during 184 days while producing only slight amounts of nitrite (4.60 ± 0.004 μM); no benzene was mineralized by Bz7 during 184 d, and no nitrite was detected. The 16S rRNA gene amplicon sequencing of the acetate-grown bacteria revealed consortia enriched inNocardioides(8.9%),Pseudomonas(18.2%),Rhizobiaceae(21.0%),Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium(51.4%) for Bz4 and Simplicispira(96.7%) for Bz7. The gained Bz4 consortium that mineralized benzene under anoxic condition can be further purified and explored for their metabolic potentials.