Biocatalytic Elimination of Pharmaceutics Found in Water With Hierarchical Silica Monoliths in Continuous Flow

Wassim Sebai,Clément Levard,Marie-Pierre, Belleville,Sher Ahmad,Perrine Chaurand,Nicolas Brun,Alexis Boccheciampe,Jose Sanchez-Marcano,Anne Galarneau

doi:10.3389/fceng.2022.823877

Abstract

Pharmaceutical products (PPs) are considered as emerging micropollutans in wastewaters, river and seawaters, and sediments. The biodegradation of PPs, such as ciprofloxacin, amoxicillin, sulfamethoxazole, and tetracycline by enzymes in aqueous solution was investigated. Laccase from Trametes versicolor was immobilized on silica monoliths with hierarchical meso-/macropores. Different methods of enzyme immobilization were experienced. The most efficient process was the enzyme covalent bonding through glutaraldehyde coupling on amino-grafted silica monoliths. Silica monoliths with different macropore and mesopore diameters were studied. The best support was the monolith featuring the largest macropore diameter (20 µm) leading to the highest permeability and the lowest pressure drop and the largest mesopore diameter (20 nm) ensuring high enzyme accessibility. The optimized enzymatic reactor (150 mg) was used for the degradation of a PP mixture (20 ppm each in 30 ml) in a continuous recycling configuration at a flow rate of 1 ml/min. The PP elimination efficiency after 24 h was as high as 100% for amoxicillin, 60% for sulfamethoxazole, 55% for tetracycline, and 30% for ciprofloxacin.

Highlights

Pharmaceutical products (PPs) are a group of hazardous contaminants found in wastewater in the concentration range of (Halling-Sørensen et al, 1998; Björlenius et al, 2018; Burns et al, 2018)
Control of Porosity Silica monoliths of 0.6 cm diameter and 10 cm length exhibiting a homogeneous network of macropores as shown by scanning electron microscopy (SEM) pictures (Figure 2) were synthesized by a combination of spinodal decomposition and sol-gel process using polyethylene oxide (PEO) of 20 and 100 kDa in acidic aqueous medium in the presence of tetraethyl orthosilicate (TEOS)
Methods of Enzyme Immobilization Reactors formed by silica monoliths (0.6 cm diameter, 0.5 cm length, 50 mg) grafted with amino function (1.5 NH2 per nm2) and cladded with FEP gains at 180°C were used for laccase immobilization following 3 methods: (1) covalent grafting by coupling with GLU or glyoxal, (2) electrostatic interactions, and (3) adsorption followed by reticulation into the mesopores with cross-linkers as GLU or poly(ethylene glycol) diglycidyl ether (PEGDGE) (CLEA method) (Figure 1)

Summary

Introduction

Pharmaceutical products (PPs) are a group of hazardous contaminants found in wastewater in the concentration range of (ng L−1–μg L−1) (Halling-Sørensen et al, 1998; Björlenius et al, 2018; Burns et al, 2018). Oxidoreductase enzymes have been employed for the degradation of many recalcitrant PPs in wastewater. Oxidoreductase enzymes have shown catalyzing complex chemical reactions with high efficiency and selectivity at mild operational conditions. Different oxidoreductase enzymes such as peroxidases, tyrosinase, and laccases have been studied for PP degradation; laccases obtained from fungi (Shraddha et al, 2011) are most commonly applied for PP degradation (Singh Arora and Kumar Sharma, 2010; Demarche et al, 2012; de Cazes et al, 2014a). The widespread application of laccase stems from its low selectivity and ability to catalyze the oxidation reactions of a range of substrates such as ortho- and paradiphenols, methoxy-substituted phenols, aromatic amines, phenolic acids, and several other compounds via a singleelectron oxidation mechanism (Pype et al, 2019)

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Conclusion