Prospective Approach to the Anaerobic Bioconversion of Benzo- and Dibenzothiophene Sulfones to Sulfide

Sulfur recovery from organic molecules such as toxic sulfones is an actual problem, and its solution through the use of environmentally friendly and nature-like processes looks attractive for research and application. For the first time, the possible bioconversion of organic sulfones (benzo-and dibenzothiophene sulfones) to inorganic sulfide under anaerobic conditions with simultaneous biogas production from glucose within a methanogenesis process is demonstrated. Biogas with a methane content of 50.7%-82.1% was obtained without H₂S impurities. Methanogenesis with 99.7%-100% efficiency and 97.8%-100% conversion of benzo- and dibenzothiophene sulfones (up to 0.45 mM) to inorganic sulfide were obtained in eight days by using a combination of various anaerobic biocatalysts immobilized in a poly(vinyl alcohol) cryogel. Pure cell cultures of sulfate-reducing bacteria and/or H₂-producing bacteria were tested as additives to the methanogenic activated sludge. The immobilized activated sludge "enhanced" by bacterial additives appeared to retain its properties and be usable multiple times for the conversion of sulfones under batch conditions.