Biocatalytic properties of cell surface display laccase for degradation of emerging contaminant acetaminophen in water reclamation

Abstract

The surface display laccase (SDL) biocatalyst, where the enzyme laccase is displayed on the surface of biological cells through synthetic biology, provides a new opportunity to develop sustainable technologies for removal of emerging contaminants from wastewater. This study vigorously characterized biocatalytic properties of the SDL in comparison to free laccase in removing emerging contaminant acetaminophen (APAP), with the aim to understand the effect of surface display on enzyme functionality and identify the strategy to overcome the potential limitation. The SDL could effectively remove APAP. Adding redox mediators substantially improved the removal efficiency. The Michaelis–Menten kinetic analysis showed that the redox mediator 2,2‐azinobis‐3‐ethylbenzothiazoline‐6‐sulfonate could overcome the limitation of APAP accessing the active site of laccase in the SDL biocatalyst. The APAP removal rate catalyzed by the SDL in real secondary wastewater effluent was higher than that in acetate buffer; comprehensive enzyme kinetic analysis provided clear evidence that there were redox mediating compounds in the wastewater. Analysis of transformation products revealed that surface display did not change laccase functionality in terms of APAP transformation mechanism. In addition, the SDL retained 88% of the initial activity after six repeated APAP biotransformation reactions. Results from this study provide a scientific basis for developing and implementing SDL as an innovative biocatalytic material for contaminant treatment applications.

Comparison of Acetaminophen Degradation by Laccases Immobilized by Two Different Methods via a Continuous Flow Microreactor Process Scheme

“…Taken together, our findings strongly suggest that the developed biocatalysts, in conjunction with a continuous flow microreactor process scheme, are well suited as an alternative and economically appealing route for the treatment of recalcitrant micropollutants. This is in line with previous reports for microbioreactor systems with immobilized biocatalysts that indicate relatively high biocatalytic activity and pollutant removal efficiency, while maintaining cost-effectiveness because of recycling and reuse of the enzyme [ 39 ]. Future work will be dedicated to finding pathways for scaling-up and optimizing this novel process.…”

“…Currently, it is very challenging to remove such pollutants from wastewaters due to their high stability and resistance to physicochemical and biological degradation. Some of the most worrisome micropollutants include pharmaceuticals, personal care products, industrial chemicals, and pesticides [ 20 , 39 ]. Acetaminophen has become one of the most consumed pharmaceutical and personal care products in many countries; it is excreted in both native and metabolized forms to sewer systems, wastewater treatment plants, and natural environments [ 19 ].…”

“…However, high concentrations of acetaminophen may inhibit their activity significantly, making them difficult to scale-up and highly unprofitable. In contrast, laccases can carry out degradation processes of pesticides, dyes, pharmaceutical and personal care products while having low energy requirements and mild operational conditions and producing fewer undesirable pollutants after degradation [ 19 , 38 , 39 , 40 ]. Some approaches using cell surface-displayed laccase have shown acetaminophen removal efficiency of 70%, in 24 h, Wu, Y., et al (2019) [ 39 ].…”

“…In contrast, laccases can carry out degradation processes of pesticides, dyes, pharmaceutical and personal care products while having low energy requirements and mild operational conditions and producing fewer undesirable pollutants after degradation [ 19 , 38 , 39 , 40 ]. Some approaches using cell surface-displayed laccase have shown acetaminophen removal efficiency of 70%, in 24 h, Wu, Y., et al (2019) [ 39 ]. This method is based on the expression and localization of laccase on the surface of Saccharomyces cerevisiae through engineered biological machinery, allowing the enzyme to be functionally expressed on the cell surface.…”

Alternative Strategies for Microbial Remediation of Pollutants via Synthetic Biology

“…The scientists and researchers are performing the experimental setup to study the bioremediation (Yergeau et al, 2012) potential against various pollutants like oil spill, plastics, synthetic dyes, organic hydrocarbons (Yadav et al, 2015), pesticides (Jaiswal et al, 2019a), heavy metals (Hemmat-Jou et al, 2018;Lebrazi and Fikri-Benbrahim, 2018), and other xenobiotics, etc (Rucká et al, 2017;Paniagua-Michel and Fathepure, 2018;Wu et al, 2020). Considering that bioremediation is performed in an open environment rather than in a closed fermentation tank, the ecological safety of bioremediation performing bacteria must be considered.…”