Laccase-immobilized on superparamagnetic iron oxide nanoparticles incorporated polymeric ultrafiltration membrane for the removal of toxic pentachlorophenol.

A biocatalytic membrane offers an ideal alternative to the conventional treatment process for the removal of toxic pentachlorophenol (PCP). The limelight of the study is to utilize superparamagnetic iron oxide nanoparticles (SPIONs) incorporated (poly (methyl vinyl ether-alt-maleic acid) (PMVEAMA) and poly (ether - ether) sulfone (PEES)) membrane for immobilization of laccase and its application towards the removal of PCP. In regard to immobilization of Tramates versicolor laccase onto membranes, 5 mM glutaraldehyde with 10 h cross-linking time was employed, yielding 76.92% and 77.96% activity recovery for PEES/PMVEAMA/La and PEES/PMVEAMA/SPIONs/Lac, respectively. In the context of kinetics and stability studies, the immobilized laccase on PEES/PMVEAMA/Lac membrane outperforms the free and PEES/PMVEAMA laccases. At pH 7.0, the free enzyme loses half of its activity, while the immobilized laccases maintained more than 87% of their initial activity even after 480 min. With regard to PCP removal, the removal efficiency of immobilized laccase on the membrane was more than free enzyme. With 100 ppm of PCP, immobilized laccase on PEES/PMVEAMA/SPIONs membrane at pH 4.0 and 50 °C had a removal efficacy of 61.65% in 24 h. Furthermore, to perk up the removal of PCP, the laccase-aided system with mediators was investigated. Amongst, veratryl alcohol displayed 71.04% of PCP removal using immobilized laccase. The reusability of the laccase heightened after immobilization on PEES/PMVEAMA/SPIONs portraying 62.44% of the residual activity with 39.4% of PCP removal even after five cycles. The current investigation reveals the efficacy of the mediator-aided PEES/PMVEAMA/lac membrane system towards removing PCP from the aqueous solution, which can also be proposed for a membrane bioreactor.

Removal of pentachlorophenol and phenanthrene from lignocellulosic biorefinery wastewater by a biocatalytic/biosurfactant system comprising cross-linked laccase aggregates and rhamnolipid.

Synthesis and characterization of highly active cross-linked laccase aggregates (CLLAs) were performed and evaluated for removal of pentachlorophenol and phenanthrene from lignocellulosic biorefinery wastewater. Laccase from Tramates versicolor MTCC 138 was insolubilized as CLLAs via precipitation with 70% ammonium sulphate and simultaneous cross-linking with 5 mM glutaraldehyde to obtain activity recovery of 89.1%. Compared to the free laccase, the pH and thermal stability of the prepared CLLAs were significantly higher. At a high temperature of 60 °C, free laccase had a half-life of 0.25 h, while CLLAs had a half-life of 6.2 h. In biorefinery wastewater (pH 7.0), the free and CLLAs were stored for 3 day at a temperature of 30 °C. Free laccase completely lost their initial activity after 60 h; however, the CLLAs retained 39% activity till 72 h. Due to its excellent stability, free laccase and CLLAs were assessed for removing pentachlorophenol and phenanthrene in wastewater. CLLAs could remove 51-58% of pentachlorophenol (PCP) and phenanthrene (PHE) in 24 h. Biosurfactants, including surfactin, sophorolipid, and rhamnolipid, were assessed for their aptitude to improve the removal of organic contaminants in wastewater. Biorefinery wastewater incubated with all surfactants enhanced PCP and PHE removal compared to the no-surfactant controls. Further, 1 µM rhamnolipid significantly amplified pentachlorophenol and phenanthrene removal to 81-93% for free laccase and CLLAs, respectively.

Insolubilization of Tramates versicolor laccase as cross-linked enzyme aggregates for the remediation of trace organic contaminants from municipal wastewater.

The novelty of this study deals with the biocatalytic treatment of trace organic contaminants (TrOCs) from municipal wastewater by insolubilized laccase. Laccase from Trametes versicolor was aggregated by three-phase partitioning technique followed by cross-linking with glutaraldehyde to produce insolubilized laccase as cross-linked enzyme aggregates (CLEAs). The optimal conditions for CLEAs preparation include ammonium sulphate concentration of 83% (w/v), crude to t-butanol ratio of 1.00: 1.05 (v/v), pH 5.3, and glutaraldehyde concentration of 20 mM obtained via statistical design. The efficiency of insolubilization of the CLEAs laccase based on the kcat/km ratio was approximately 4.8-fold greater than that of free laccase. The developed CLEAs showed greater resistance to product inhibition mediated by ABTS than the free enzyme and exhibited excellent catalytic activity even after the tenth successive cycle. Further, free laccase and the synthesized CLEAs laccase were utilized to treat five analgesics, two NSAIDS, three antibiotics, two antilipemics, and three pesticides in the municipal wastewater. Under the batch process with operating conditions of pH 7.0 and 20 °C, 1000 U/L of CLEAs, laccase removed 11 TrOCs in the range of about 20-99%. However, the inactivated CLEAs only adsorbed 2-25% of TrOCs. It was observed that acetaminophen, mefenamic acid, trimethoprim, and metolachlor depicted almost complete removal with CLEAs laccase. The performance of CLEAs laccase in a perfusion basket reactor was tested for the removal of TrOCs from municipal wastewater.

Performance study of fouling resistant novel ultrafiltration membranes based on the blends of poly (ether ether sulfone)/poly (vinyl pyrrolidone)/nano-titania for the separation of humic acid, dyes and biological macromolecular proteins from aqueous solutions.

This study explains the use of a ultrafiltration membrane made of polyvinyl pyrrolidone (PVP) and poly(ether ether sulfone) (PEES)/Nano-titania (n-TiO2) for the separation of organic compounds. The results of the tests for porosity, water content, surface chemistry, membrane morphology, and contact angle demonstrated that the developed membranes have more hydrophilicity than PEES membranes due to the redundant hydrophilic nature of PVP and n-TiO2. The membrane pure water flux, which contains 5 wt% PVP and 1.5 wt% n-TiO2, was 312.76 Lm-2h-1, about three-fold higher than that of pristine membrane (95.71 Lm-2h-1). Employing bovine serum albumin as a model foulant, the fouling resistance of the PEES/PVP/n-TiO2 membrane was examined. According to the analysis of flux recovery ratio and irreversible resistance, modified membranes were less likely to foul, and the PEES/n-TiO2 membrane with 5% PVP addition was recommended as optimal. The fabricated membranes effectively removed more than 95% of various organic compounds such as humic acid, safranin O, egg albumin, pepsin, and trypsin from aqueous solution. Permeability of safranin O and humic acid of PEES/PVP/n-TiO2 membranes was about 118 Lm-2h-1 and 138 Lm-2h-1, respectively.