Assessing the use of nanoimmobilized laccases to remove micropollutants from wastewater

Abstract

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.

Evaluation of the applicability of the aquatic ascomycete Phoma sp. UHH 5‐1‐03 for the removal of pharmaceutically active compounds from municipal wastewaters using membrane bioreactors

“…Batch degradation experiments were performed in order to assess the removal of micropollutants by Phoma sp., thereby verifying the activity of the fungus toward target pollutants at their environmentally relevant trace concentrations, and previously reported removal mechanisms involved [15]. Time courses of relative concentrations (initial = 100%; please refer to Supporting Information Table S1 for the corresponding absolute value) of DF, which is known to be directly oxidized by laccase [15,23,24], in batch tests employing active Phoma sp. with stimulated laccase production and in experiments containing the active fungus without stimulated laccase production are depicted in Fig.…”

The Protagonism of Biocatalysis in Green Chemistry and Its Environmental Benefits

“…Laccases immobilized onto silica nanoparticles have been used to remove bisphenol from secondary effluent in a municipal wastewater treatment plant [96] as well as phenol from coking wastewater [97]. There are many studies on the synthesis and comparison of SENs with free enzymes; however, SEN applications for wastewater treatment are still in the rational design phase [98,99].…”

Formulation of Laccase Nanobiocatalysts Based on Ionic and Covalent Interactions for the Enhanced Oxidation of Phenolic Compounds

“…The rationale behind the high activity yields is attributed to the fact that immobilized laccases on this type of support would have high affinity for standard substrates such as ABTS. For instance, Arca-Ramos et al [42] reported the hyperactivation of laccase from T. versicolor after the formation of covalent bonds with silica nanoparticles; whereas Matijosyte et al [11] described a similar behavior for laccase from T. villosa (activity recovery up to 148%) after the formation of cross-linking aggregates (CLEAS ® , CLEATechnologies, Delft, The Netherlands).…”

“…Lower activity of immobilized laccase towards phenolic substrates has also been previously reported. For instance, Arca-Ramos et al [42] found that bisphenol A degradation rate was much slower for immobilized laccases (from 6-to 26-fold lower than that of the free enzyme). This lower reaction rate was related to the potential aggregation of the nanoparticles which could reduce substrate accessibility.…”