Optimization of restrictive factors during process of removing sulfide into elemental sulfur by sulfur oxidizer

Abstract:

[Objective] Concerning the special biochemical characteristics of sulfur oxidizer, we optimized related restrictive factors during the process of oxidizing sulfide to elemental sulfur for improving productivity of the elemental sulfur. [Methods] A typical desulfurization strain Thermithiobacillus tepidarius JNU-2 (T. tepidarius JNU-2) was used for oxidizing sulfide into elemental sulfur. The culture trait and desulfurization performance was respectively studied with Na2S2O3 as the energy substrate. Then the process of oxidizing sulfide into elemental sulfur related restrictive factor was optimized via single factor experiments. [Results] With Na2S2O3 as the sole energy substrate, μmax of T. tepidarius JNU-2 was 0.207 h?1 and the final biomass was 4.0×106 cells/mL. Nearly 98% Na2S2O3 had been consumed at 24 h and elemental sulfur production reached the maximum value 0.8 g/L. Then elemental sulfur was gradually oxidized and eventually maintained at 0.2 g/L. The optimum conditions of major restrictive factors such as carbon and nitrogen source, MgSO4, FeSO4 and energy substrate was determined through the single factor experiments as follow. CO2, NH4Cl 0.5 g/L, MgSO4 0.5 g/L, FeSO4 0.1 g/L, Na2S2O3 15.0 g/L. After optimization, the maximum biomass reached 4.0×106 cells/mL during the process of oxidizing Na2S2O3 into elemental sulfur and its titer was increased to 1.14 g/L, which was improved by 42.5% compared to the previous non-optimized one. [Conclusion] The efficiency of elemental sulfur from oxidizing sulfide by chemoautotrophic T. tepidarius JNU-2 could be effectively improved via optimization of major restrictive factors.