Removal of dyes released in water by textile industries presents a major challenge for the researchers. Soybean peroxidase (SBP) has been widely explored for removal of a variety of toxic aromatics consisting of phenolic or anilino functional groups. Also, it has been known to possess the ability of azo-bond cleavage. This thesis was aimed to investigate azo-bond cleavage by SBP in the presence of hydrogen peroxide, if possible, in the absence of these functional groups. Direct Yellow 12 and azobenzene were chosen as a model compounds for this study. Experiments were conducted at a range of pHs, SBP and hydrogen peroxide to investigate the hypothesis. Enzymatic removal of p-anisidine and Methyl Orange (MO) and azo-bond cleavage of MO were also studied. Optimization of pH, hydrogen peroxide-to-substrate ratio and SBP activity were performed to achieve ≥95% removal of these substrates in 3 hours, analyzed using high-performance liquid chromatography. A time course study was conducted to calculate pseudo-first-order rate constants and half-lives for degradation of these compounds. Mass spectrometry analysis showed oligomerization of p-anisidine and for MO, evidence of azo-bond cleavage was obtained after the enzymatic treatment
