Cell Surface Display Fungal Laccase as a Renewable Biocatalyst for Degradation of Persistent Micropollutants Bisphenol A and Sulfamethoxazole

Fungal laccases have high activity in degrading various persistent organic pollutants. However, using enzymes in solution for water treatment has limitations of nonreusability, short enzyme lifetimes, and high cost of single use. In this study, we developed a new type of biocatalyst by immobilizing fungal laccase on the surface of yeast cells using synthetic biology techniques. The biocatalyst, referred to as surface display laccase (SDL), had an enzyme activity of 104 ± 3 mU/g dry cell (with 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonate (ABTS)). The SDL retained over 90% of the initial enzyme activity after 25 days storage at room temperature, while, in contrast, activity of free laccase declined to 60% of its initial activity. The SDL could be reused with high stability as it retained 74% of initial activity after eight repeated batch reactions. Proof-of-concept evaluations of the effectiveness of SDL in treating contaminants of emerging concern were performed with bisphenol A and sulfamethoxazole. Results from contaminant degradation kinetics and the effects of redox mediator amendment provided insights into the factors affecting the efficacy of the SDL system. This study reports, for the first time, the development of a surface display enzyme biocatalyst as an effective and renewable alternative for treating recalcitrant organic micropollutants.