Biodegradation of azo dye Reactive Black 5 by strict anaerobe Clostridium acetobutylicum and evaluation of its effects for hydrogen production

As azo dyes are commercially used to treat textiles and leather articles, but they were toxic, allergenic, carcinogenic, and mutagenic to human and environment if they were not well treated, the content and degradation of azo dyes in wastewater were very important. So far, various methods such as physical, chemical, and biological methods have been applied to solve this. As a sequential work, we tried to remove a famous azo dye, Reactive Black 5 (RB5) by biological assay and found that Clostridium acetobutylicum showed the best decolorization of RB5 among the hydrogen producing Clostridium species examined. It was also found 100 ppm concentration of RB5 did not affect biohydrogen production of C. acetobutylicum suggesting simultaneous degradation of azo dye and biohydrogen production was possible. Optimal condition for simultaneous decolorization and biohydrogen production was selected as pH 6, 40 °C, and 200 rpm, and high concentration (200 ppm) of RB5 could be decolorized up to 97%. When C. acetobutylicum was examined for further decoloring activities, it was showed the decolorization of various dyes such as Bromophenol, Bromocresol, Methyl Red, and Reactive Red 120. This study showed potential application of C. acetobutylicum in wastewater treatment by simultaneous decolorizing and biohydrogen production.