Exogenous DBT and overexpression of deoR improved the waste tire rubber desulfurization ability of a newly isolated Escherichia sp. strain

Abstract

The environmental hazards caused by accumulation of waste tire rubber (TR) constitute a major global concern. Microbial desulfurization is an environmentally friendly method for treating waste TR for recycling; it is characterized by mild reaction conditions and low generation of harmful pollutants. Here, we report a new microorganism, Escherichia sp., which was isolated from waste tire surfaces and has the ability to desulfurize TR. Exogenous dibenzothiophene (DBT) increased the cell growth and TR desulfurization ability of Escherichia sp. in a desulfurization medium containing TR. Transcriptomic analysis revealed that TR-only treatment significantly upregulated the expression of the 4S desulfurization pathway gene and six transcription factors, and TR-DBT cotreatment further increased the upregulation of these genes compared with TR-only treatment in Escherichia sp. Overexpression of these six transcription factors in Escherichia sp. revealed that, deoR, was the most effective at increasing transcription of 4S genes and enhancing the TR desulfurization ability. In addition, exogenous DBT and deoR overexpression enhanced the ability of Escherichia sp. to decrease the intensities of CC and C-S bonds and increased the intensities of SO and OSO bonds. Our report establishes a TR desulfurization strategy involving exogenous DBT treatment or deoR overexpression in a new Escherichia sp. strain.