Hydrogen sulfide oxidation under anoxic conditions by a nitrate-reducing, sulfide-oxidizing bacterium isolated from the Mae Urn Long Luang hot spring, Thailand

Biological removal of hydrogen sulfide (H2S) has been widely practiced across the world because it overcomes the drawbacks associated with physico-chemical processes. In this study, the role of a novel MAL 1HM19 strain of a nitrate-reducing, sulfide-oxidizing bacterium (NR-SOB) isolated from the Mae Urn Long Luang hot spring (Thailand) was investigated in batch systems for H2S removal under different initial N-NO3- concentrations (60,120 and 240 mg N-NO3-/L) at 35 degrees C. The strain MAL 1 HM19 was capable of removing 100% of the gas-phase H2S within 10 h of incubation. In the liquid-phase, the final products depended on the initial N-NO3- concentration: at 120 and 240 mg N-NOVL, 15% and 18% SO42- formation was detected, while no SO4 was detected at an initial N-NO3- concentration of 60 mg N-NOVL. The identification of strain MAL 1HM19, based on the 16S rDNA nucleotide sequence, revealed it was closely related to Paracoccus sp. (99.93% similarity). The soxB gene was present in strain MAL 1HM19. In addition, strain MAL 1HM19 showed a good capacity to grow at several NaCl concentrations (0.03-7% w/v), at temperatures varying between 20 and 50 degrees C and within the pH range of 7.0-9.0. (C) 2017 Elsevier Ltd. All rights reserved.