Sulfur-oxidising ability of bacteria isolated from soil samples in Akure, Nigeria: Site-linked evaluation

Abstract

Sulfur oxidising bacteria (SOB) are of great importance in the sulfur biogeochemical cycle and removal of undesirable hydrogen sulfide in biogas production. This study evaluated the sulfide oxidising ability of bacteria from different soils using bromocresol purple dye reduction method and spectrophotometry. The study sites were the abattoir, automobile workshop, dumpsite, rhizospheric soil, and sewer disposal sites. Starkey broth was used as a selective culture broth and sodium thiosulfate as an enrichment culture medium, both at pH 8.00. Sulfur ion evaluation was carried out using spectrophotometry at 450 nm wavelength. 16S rRNA sequencing of promising SOB was investigated. The total colony count of sulfur oxidising bacteria able to reduce the bromocresol dye on the sodium thiosulfate agar ranged from 2.00 × 103 cfu/g from the abattoir, dumpsite and sewer disposal sites to 1.50 × 104 cfu/g from the automobile workshop. Paenibacillus ripae and Staphylococcus aureus had the highest sulfur oxidation absorbance of 1.72 and 1.65 with a pH of 5.75 and 5.90 respectively. The pH of the studied bacteria on the sixth day of incubation ranged from 5.69 to 6.03. Bacillus cereus, P. ripae and S. aureus demonstrated most promising potential as sulfur oxidising agents. This work revealed the presence of SOB from different locations with relatively low pH and indicates potential importance of studied bacteria in the removal of hydrogen sulfide in biogas that may not support bio-corrosion.