Semi-continuous desulfurization of natural gas in photobioreactor by green sulfur-oxidizing bacterial consortia isolated
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ORIGINAL ARTICLE
Semi-continuous desulfurization of natural gas in photobioreactor by green sulfur-oxidizing bacterial consortia isolated from hot spring Hanieh Sharifian-Koupaiee 1,2 & Nafiseh Sadat Naghavi 1
&
Tooraj Tavakoli-Ghinani 3
Received: 2 March 2020 / Revised: 18 September 2020 / Accepted: 9 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Anoxygenic phototrophic bacteria are able to oxidize and remove hydrogen sulfide from natural sources by using inorganic substrates and light. In the present study, anoxygenic phototrophic bacteria were isolated from Vartoon hot spring (east of Isfahan Province, Iran) and used for removal of sulfide compounds from natural gas in a semi-continuous photobioreactor. Mat samples that obtained from the depth of spring were introduced into Winogradsky columns and kept in the presence of sunlight for 3–4 months until green and purple layers were composed. The layers were then transferred into mineral medium and incubated under anaerobic condition. The sequence of amplified 16S rDNA in green bacteria and an amplified sequence among the gene encoding photosynthetic reaction center in purple bacteria were used for molecular identification of bacteria. The bacterial growth based on the contents of bacteriochlorophylls and the extent of elemental sulfur production by the cells were measured after ethanol extraction. Molecular identification validated the presence of Chlorobium phaeobacteroides and Prosthecochloris vibrioformis from green sulfur bacteria in the consortium. The results indicated the most increase in bacteriochlorophylls c, d, and e content of mineral medium after bacterial growth. In addition, by releasing 62.4 mmol elemental sulfur, 79.30% increase was detected in sulfur content of the medium during 3 weeks. The consortium of sulfur-oxidizing phototrophic bacteria was potentially used for natural gas desulfurization in the semi-closed photobioreactor. This system is suggested as a replacement for chemoautotrophic systems in areas where there is sufficient access to sunlight. Keywords Natural gas . Desulfurization . Anoxygenic phototrophic bacteria . Photobioreactor
1 Introduction Chemolithotrophs such as Acidithiobacillus ferrooxidans have been commonly used for the removal of sulfur compounds from the environment, but these bacteria are not able to remove organic sulfur and require relatively high oxygen amounts (higher than 5%) and acidic pH range (1.5–3.5) to maintain their oxidization activity. On the other hand, exact control of the oxygen concentration is required when using
* Nafiseh Sadat Naghavi [email protected]; [email protected] 1
Department of Microbiology, Falavarjan Branch, Islamic Azad University, Isfahan, Iran
2
Department of Microbiology, College of Science, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
3
Department of Chemical Engineering, Isfahan University, Isfahan, Iran
chemoautotrophic bacteria to produce elemental sulfur instead of sulfate. Therefore, some sulfate is pro
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