Bio-Fenton Systems with Glucose Oxidase Expressed in Pichia pastoris for Degradation of Dyes and Lignin

Abstract

The Fenton reaction is an efficient and sustainable approach for the degradation of recalcitrant pollutants, such as lignin and synthetic dyes. This process relies on hydroxyl radicals (•OH), which possess with standard reduction potential of +2.8 V and non-specifically oxidize organic compounds to acquire electrons. The generation of hydroxyl radicals requires hydrogen peroxide (H₂O₂) and Fe²⁺/Fe³⁺ as key reactants. Based on this mechanism, the present study aims to enhance the degradation efficiency of recalcitrant pollutants by establishing a Bio-Fenton system using Pichia pastoris X-33 engineered to express glucose oxidase (GOX) for the continuous in-situ production of H₂O₂. In this study, the pPICZα-A expression vector was employed to drive the expression of extracellular of glucose oxidase (GOX) from Penicillium amagasakiense in P. pastoris X-33. Additionally, the CTA1 gene encoding catalase in P. pastoris was knocked out to prevent the decomposition of H₂O₂ generated by the glucose oxidase activity. A Bio-Fenton system incorporating Fe(III)-citrate (0.5 mM) as a catalyst was applied to degrade guaiacylglycerol-β-guaiacyl ether (GGGE), a lignin model compound derived from wood, as well as synthetic dyes such as methylene blue and indigo carmine. The results showed that GGGE was degraded by over 80% within 7 days, and methylene blue and indigo carmine were successfully degraded within 120 minutes and 72 hours, respectively. This study demonstrates the potential of a Bio-Fenton system based on the sustainable supply of H₂O₂ from microbial sources as an efficient and environmentally friendly technology for treating recalcitrant pollutants. The findings highlight its applicability in advancing green and sustainable approaches to pollutant management.