Hydrogen sulfide elimination from natural gas by native isolated bacteria from hot-spring

Abstract

Recently due to strict environmental regulations, concentration of hazardous organic sulfur compounds from gas stream should be reduced. A new efficient method for removal of hydrogen sulfide from natural gas is required. Conventional methods for desulfurization are very costly and required solvent, high operation temperature, and pressure. In contrary, biological processes have great potential to eliminate hydrogen sulfide under mild conditions. Extensive research has been conducted on sulphur oxidizing bacteria for the removal of hydrogen sulfide. However, with present achievements is still not enough to satisfy the industrial requirements. To improve the biodesulfurization efficiency additional research required to isolate a particular strain organism. In this article the ability of newly isolated bacteria was discussed. For this purpose the mixed culture was isolated from native hot spring in the hill side of Damavand Mountain (in North of Iran). The isolated culture was inoculated on nutrient plate agar under anaerobic condition. After incubation for duration 72 h two distinct colonies white and yellow color were observed. Each species was separately grown in nutrient broth and then the optimal conditions were obtained. The desired conditions for white colony such as temperature, pH and agitation rate were 36˚C, 6.5 and 180 rpm, respectively. All the above conditions for yellow colony were identical except for pH slightly reduced to 6. On the basis of optimal biodesulfurization conditions, maximum cell dry weight for the each isolated specie was achieved; approximately were 1.35 and 1.12 g.l-1 for white and yellow colony respectively. The removal of hydrogen sulfide from natural gas stream as the aim of present work was obtained. The percentage removals were 67 and 35% for white and yellow colony, respectively.