CONICET | Buscador de Institutos y Recursos Humanos

Sulfate-reducing microorganisms (SRM) constitute a group of anaerobic organismsfrequently found in anoxic environments. These microorganisms employ sulfate as theirfinal electron acceptor during metabolism, leading to the generation of sulfide anions.Industries, such as Oil & Gas production, suffer huge economic losses in consequenceof SRM growth and consequent sulfide production, due to their involvement inMicrobiologically Influenced Corrosion (MIC). The prevalent method for SRM detection inindustry is the Most Probable Number assay (MPN), which may require up to 28 days forgetting results. Over the past decades, diverse methods (microscopy techniques, molecularbiology techniques, enzymatic techniques, microbiological techniques) with differingcomplexities, costs, and time demands have been developed to identify and monitor SRMin industrial environments. However, the use of costly high-tech equipment and therequirement for highly skilled professionals, have hindered their practical field applicationover the MPN technique.SRM can proliferate at various pH levels, generally below 8. At these pH levels, sulfidespeciation yields minimal free sulfide species concentrations (S-2), which fall beyond theanalytical range of the Nernst equation for the electrode (over 10-6 mol L-1). Lower sulfideconcentrations, exhibits a super-Nernstian response in the equilibrium, unsuitable forprecise analytical quantification. However, in the case of biological respiration, this yieldsan exceedingly sensitive response that differentiates sulfate-reducing metabolism fromothers in a semi-quantitative manner.This study presents a methodology for highly sensitive detection of SRM metabolicactivity in aqueous media, based on tracking changes in the equilibrium potential of anAg/Ag2S electrode, caused by the presence of biogenic sulfide. We constructed the Ag/Ag2S electrode and evaluated its response under distinct pHconditions, growth media, microbial metabolism, and abiotic system. We assessed thesensor both, as an external unit for culture testing and as an internal culture sensor forcontinuous monitoring. Detection times of the sensor were found to be lower than those ofMPN and to lower cell counts.Through time response assays we effectively linked the growth of an SRM culture to thesensor´s output in a media inoculated with a cell count as low as 102 SRM mL-1, whichactivity could be identified in less than 24 hours. With this data, we established an SRMquantitative estimation based on the sensor´s readings for a laboratory-grade culture, whichcan be applicable for quick SRM microorganism estimation in the field.This innovative approach can be used on-site with minimal technical, professional, andequipment requirements and bridges the gap between detection events and application ofpreventive measures, such as biocides dosage

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