Assessing the use of nanoimmobilized laccases to remove micropollutants from wastewater.
Enzymes immobilization is a useful way to allow enzyme reuse and increase their stability. A high redox potential laccase from Trametes versicolor (TvL) and a low redox potential, but commercially available low-cost laccase from Myceliophthora thermophila (MtL), were successfully immobilized and co-immobilized onto fumed silica nanoparticles (fsNP). Enzyme loads of 1.78 ± 0.07, 0.69 ± 0.03, and 1.10 ± 0.01 U/mg fsNP were attained for the optimal doses of TvL, MtL, and co-immobilized laccases, respectively. In general, the laccase-fsNP conjugates showed a higher resistance against an acidic pH value (i.e., pH 3), and a higher storage stability than free enzymes. In addition, immobilized enzymes exhibited a superior long-term stability than free laccases when incubated in a secondary effluent from a municipal wastewater treatment plant (WWTP). For instance, the residual activity after 2 weeks for the co-immobilized laccases and the mixture of free laccases were 40.2 ± 2.5% and 16.8 ± 1.0%, respectively. The ability of the laccase-fsNP to remove a mixture of (14)C-bisphenol A (BPA) and (14)C-sodium diclofenac (DCF) from spiked secondary effluents was assessed in batch experiments. The catalytic efficiency was highly dependent on both the microbial source and state of the biocatalyst. The high redox potential TvL in free form attained a four-fold higher percentage of BPA transformation than the free MtL. Compared to free laccases, immobilized enzymes led to much slower rates of BPA transformation. For instance, after 24 h, the percentages of BPA transformation by 1000 U/L of a mixture of free laccases or co-immobilized enzymes were 67.8 ± 5.2 and 27.0 ± 3.9%, respectively. Nevertheless, the use of 8000 U/L of co-immobilized laccase led to a nearly complete removal of BPA, despite the unfavorable conditions for laccase catalysis (pH ~ 8.4). DCF transformation was not observed for any of the enzymatic systems, showing that this compound is highly recalcitrant toward laccase oxidation under realistic conditions.
Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain. adriana.arca@rai.usc.es.
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Arca-Ramos
Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, Gründenstrasse 40, Muttenz, 4132, Switzerland.
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Ammann
Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, Gründenstrasse 40, Muttenz, 4132, Switzerland.
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Gasser
Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, Gründenstrasse 40, Muttenz, 4132, Switzerland.
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Nastold
Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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Eibes
Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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Feijoo
Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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Lema
Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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Moreira
Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, Gründenstrasse 40, Muttenz, 4132, Switzerland.|State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University Xianlin Campus, Xianlin Avenue 163, Nanjing, 210023, China.
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Corvini
D001559:Benzhydryl Compounds; D002384:Catalysis; D004800:Enzymes, Immobilized / Q000378:metabolism*; D042845:Laccase / Q000378:metabolism*; D053758:Nanoparticles / Q000378:metabolism; D010084:Oxidation-Reduction; D010636:Phenols; D012822:Silicon Dioxide / Q000737:chemistry; D055454:Trametes / Q000201:enzymology; D062065:Wastewater / Q000737:chemistry; D018508:Water Purification / Q000379:methods*; D000098826:Bisphenol A Compounds
D001559:Benzhydryl Compounds; D004800:Enzymes, Immobilized; D042845:Laccase; D010636:Phenols; D012822:Silicon Dioxide; D062065:Wastewater; C006780:bisphenol A; D000098826:Bisphenol A Compounds
Enzyme immobilization; Fumed silica nanoparticles; Laccase; Micropollutants; Secondary effluent