Dibenzothiophene desulfurization capability and evolutionary divergence of newly isolated bacteria
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ORIGINAL PAPER
Dibenzothiophene desulfurization capability and evolutionary divergence of newly isolated bacteria Nasrin Akhtar1 · Muhammad A. Ghauri1 · Kalsoom Akhtar1
Received: 22 November 2015 / Revised: 11 February 2016 / Accepted: 2 March 2016 © Springer-Verlag Berlin Heidelberg 2016
Abstract Metabolically microorganisms are diverse, and they are capable of transforming almost every known group of chemical compounds present in coal and oil in various forms. In this milieu, one of the important microbial metabolic processes is the biodesulfurization [cleavage of carbon–sulfur (C–S) bond] of thiophenic compounds, such as dibenzothiophene (DBT), which is the most abundant form of organic sulfur present in fossil fuels. In the current study, ten newly isolated bacterial isolates, designated as species of genera Gordonia, Amycolatopsis, Microbacterium and Mycobacterium, were enriched from different samples in the presence of DBT as a sole source of organic sulfur. The HPLC analysis of the DBT grown cultures indicated the consumption of DBT and accumulation of 2-hydroxybiphenyl (2-HBP). Detection of 2-HBP, a marker metabolite of 4S (sulfoxide–sulfone–sulfinate–sulfate) pathway, suggested that the newly isolated strains harbored metabolic activity for DBT desulfurization through the cleavage of C–S bond. The maximum 2-HBP formation rate was 3.5 µmol/g dry cell weight (DCW)/h. The phylogenetic analysis of the new isolates showed that they had diverse distribution within the phylogenetic tree and formed distinct clusters, suggesting that they might represent strains of already reported species
Communicated by Matthias Boll. Electronic supplementary material The online version of this article (doi:10.1007/s00203-016-1209-5) contains supplementary material, which is available to authorized users. * Nasrin Akhtar [email protected]; [email protected] 1
Industrial Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, P. O. Box 577, Jhang Road, Faisalabad, Pakistan
or they were altogether new species. Estimates of evolutionary divergence showed high level of nucleotide divergence between the isolates within the same genus. The new isolates were able to use a range of heterocyclic sulfur compounds, thus making them suitable candidates for a robust biodesulfurization system for fossil fuels. Keywords Dibenzothiophene · Organic sulfur · C–S bond cleavage · 16S rRNA gene · Phylogenetic analysis
Introduction Fossil fuels (coal and oil) contain various heterocyclic organosulfur-containing compounds, including alkylated and non-alkylated forms of dibenzothiophene (DBT) and benzothiophene (BT). Combustion of fossil fuels generates many waste products. In this context, sulfur dioxide is one of the most noxious gases, which have bad effects on environment, plants, humans and animals’ health. Therefore, environmental regulations around the world have been demanding a reduction in the sulfur contents, requiring concentrations lower than 15 ppm (Bhatia and Sharma 2010; Maass et al. 2015; Nu
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