A New Strategy for the Enzymatic Degradation of Sudan Dyes in Non-alkaline Conditions

Abstract

Sudan dyes are widely used as coloring agents in various solvents, waxes, and polishes. However, the dyes are environmental contaminants and Sudan I is a weak carcinogen, and its removal from wastewater remains challenging. Here, we developed a new strategy for Sudan dye degradation for use in the non-alkaline conditions typically found in wastewater. By combing glucose oxidase (GOD) and horseradish peroxidase (HRP), we avoided the hydrogen peroxide-induced HRP damage and inactivation. Moreover, the GOD-HRP-coupled degradation of Sudan dyes were enhanced by the addition of different kinds of phenols. Systematic investigations were carried out to determine the optimal process parameters (i.e., phenol concentration, pH value, temperature, and enzyme dose) for degrading Sudan I with GOD and HRP. Also, this strategy could be applied to degradation of Sudan II and Sudan III. We were also able to co-express GOD and HRP in a prokaryotic-like polycistronic expression system in Pichia pastoris, based on the internal ribosome entry sites (IRES). Therefore, this fermented liquid containing GOD and HRP might be used in the future to degrade pollutants in weakly acidic conditions.