ABSTRACT
Thiosulfate, as a contaminant, can be bio-transformed by Sulfur-Oxidizing-Bacteria (SOB) into various less toxic products, e.g., elemental sulfur (S0). In this study, the distribution of thiosulfate bio-oxidation products was studied in shake flasks and bioreactors using an indigenous SOB consortium. Original cells enriched at 400 ppm thiosulfate completely bio-transformed 700 ppm thiosulfate into 65% sulfate and 5% sulfur. Cells maintained on solid (liquid) medium were used to prepare active consortium (1-day-old), which resulted in an S0 formation of 230 ppm (155 ppm) during 3000 ppm thiosulfate oxidation as compared to 6 ppm (97 ppm) using 8-day-old cells. Thiosulfate bio-oxidation at a higher level (4000 ppm) was examined in a magnetically stirred bioreactor at 1 and 2 vvm aerations. After 40 h, thiosulfate was fully oxidized at 2 vvm while only 43% oxidation was obtained at 1 vvm. However, maximum S0 formation of 44% alongside complete thiosulfate oxidation at 3000 ppm, was obtained in a stirred reactor at 60 rpm and 36 h with 1 vvm aeration. Our enriched SOB consortium was, therefore, well capable of biotransformation of thiosulfate into S0, which is an intermediate product with multipurpose applications.
