Biodegradation of ethanethiol in aqueous medium by a new Lysinibacillus sphaericus strain RG-1 isolated from activated sludge.

In the present study, a new bacterial strain isolated from activated sludge has been identified as Lysinibacillus sphaericus based on its morphology, physiochemical properties, and the results of 16S ribosomal RNA (rRNA) gene sequence analysis. This new bacterial strain uses ethanethiol as both carbon source and energy source. The key factors for controlling the degradation efficiency of ethanethiol by this strain were found to be initial ethanethiol concentration, temperature, and pH value of solutions. Under the optimized conditions, as well as 4 mg l(-1) ethanethiol, 30°C, and pH = 7.0, almost 100% ethanethiol can be degraded within 96 h and sulfate as a final product was detected in aqueous medium. The degradation reaction of ethanethiol over this newly isolated strain can be described by pseudo first-order equation in which the maximum degradation rate constant K and the minimum half-life were respectively calculated to be 0.0308 h(-1) and 22.5 h under the optimal conditions.