LAUSR

Abstract Higher activity and stability at neutral pH and tolerance toward anions have made bilirubin oxidases (BODs) proper candidates for industrial utilizations. A putative BOD from Thermosediminibacter oceani (ToBOD) exhibited high stability over a pH range of 3.5–10.0 after heterologous expression and purification. The optimal temperature for the enzyme activity was 75 °C. ToBOD displayed a high thermostability with a half-life of 180 min at 70 °C and 120 min at 80 °C, respectively. Km and Kcat values were 126.5 μM and 130.9 S−1 for ABTS, 19.6 μM and 72.5 S−1 for SGZ, and 31.2 μM and 76.2 S−1 for unconjugated bilirubin, respectively. ToBOD showed tolerance to 10% and 50% (v/v) of water-miscible organic solvents and Triton X-100 as a non-ionic surfactant. In the presence of ABTS as the mediator, ToBOD decolorized malachite green (MG) and Congo red (CR) dyes at a rate of about 63% and 71%, respectively in 2 h. Decolorization was improved within 4 h at a rate of 86% and 89% for MG and CR, respectively. Structural analyses of ToBOD showed that lower folding heat capacity, folding enthalpy, folding free energy, and side-chain hydrogen bonds have a correlation with in vitro biochemical properties.