Induced enzyme activities by acclimatised BAC-ZS mixed culture during the treatment of acid orange 7

Abstract

Azo dyes are the most common group of synthetic colourants released into the environment. Improper discharge of effluents containing azo dyes and their metabolites into the water bodies are detrimental as it generates highly coloured wastewater, and releases compounds that can be toxic, carcinogenic or mutagenic to living organisms. The acclimatised BAC-ZS mixed culture was able to decolourise azo dye, Acid Orange 7 (AO7) in a sequential facultative anaerobic-aerobic condition. The whole genome sequencing showed two possible enzymes are associated with decolourisation and degradation of AO7 which are azoreductase and NADH peroxidase. Both azoreductase and NADH peroxidase were produced intracellularly during treatment of AO7 using the sequential facultative anaerobicaerobic condition. The maximum activity of azoreductase was obtained during the facultative anaerobic condition while the maximum activity of NADH peroxidase was obtained during the aerobic condition. During the facultative anaerobic condition (2 hours of static condition), azoreductase activity was about 2 fold (0.013U/mg) higher than aerobic conditions which only produced specific activity of 0.006 U/mg. These indicated that azoreductase was induced during the facultative anaerobic condition while NADH peroxidase was mainly induced during the aerobic condition. Its highest activity was obtained during the exponential phase under aerobic condition (48 hours agitation) with specific activity of 4.63 U/mg.