An Overview of the Biochemical and Molecular Aspects of Microbial Oxidation of Inorganic Sulfur Compounds

Inorganic sulfur compounds are oxidized mostly to sulfate by microorganisms belonging to the bacteria and archaea domains. These microorganisms produce different types of enzymes, e. g., oxidoreductases and hydrolases for the metabolism of inorganic sulfur compounds. These versatile biocatalysts have potential biotechnological applications in different fields including biohydrometallurgical processes for recovering precious heavy metals and also for bioremediation of sulfides in industrial waste effluents. Appropriate knowledge on the enzymatic pathways of inorganic sulfur compounds oxidation will help to tailor the catalytic properties of these microorganisms so that they are optimal not only for a given reaction but also in the context of harsh industrial processes. This review describes the distribution of inorganic sulfur compound-oxidizing microorganisms, various enzymatic systems associated with sulfur metabolism, and identification of the gene(s) responsible for catalysis of different enzymatic reactions.