Biodegradation of malodorous mercaptans by a novel Staphylococcus capitis strain isolated from gas-washing wastewaters of the Tunisian Chemical Group

Abstract

There are increasing concerns over the harmful effects of the phosphate industry on human health and quality of life worldwide, including the Tunisian Chemical Group (GCT) in Sfax, which generates various malodorous gas fractions, such as hydrogen sulfide (H2S) and fetid mercaptans, causing nuisance to employees and local residents. Accordingly, the present study aimed to investigate the ability of an adapted microbial consortium isolated from the gas-washing wastewaters (GWWs) generated from GCT to degrade hazardous and malodorous mercaptans. A novel mesophilic bacterial strain (SH6), which was noted to display particularly high mercaptan degradation potential, was isolated from the adapted consortium growing on those GWWs and several malodorous mercaptans after enrichment on 1-dodecanethiol. The results from 16 rRNA gene sequencing and identity analysis revealed that the SH6 isolate belonged to Staphylococcus genus, with a high sequence similarity to Staphylococcus capitis (99.7 %). The SH6 strain was able to completely degrade 1-dodecanethiol, used as the sole carbon and energy source, after 72 h of incubation at 37 °C and 180 rpm. A decrease in the surface tension of cell-free culture supernatants was observed during the oxidation of dodecanethiol, suggesting the production of surface-active compounds. The stain was also able to grow on other mercaptans, such as 1,8-octanedithiol and 2,3-butanedithiol, which further supports its potential candidacy for application in the bioremediation of mercaptan-contaminated sites. Overall, the findings of the present study indicate that the SH6 strain might offer promising opportunities for the development of more adapted, efficient and cost-effective bio-disodoration strategies.