Layer-by-Layer-Assembled Laccase Enzyme on Stimuli-Responsive Membranes for Chloro-Organics Degradation

Abstract

Functionalized membranes provide versatile platforms for incorporation of bio-catalysts and nanostructured materials for efficient and benign environmental remediation. The existing techniques for remediating chloro-organics in water consist of both physical and chemical means mostly using metal oxide-based catalysts, despite associated environmental concerns. To offer bioinspired remediation as an alternative, we herein demonstrate a layer-by-layer approach to immobilize laccase enzyme into pH-responsive functionalized membranes for degradation of chloro-organics from water. Efficacy of these bioinspired membranes towards dechlorination of 2,4,6-trichlorophenol (TCP) is demonstrated under pressure driven continuous flow mode (convective flow) for the first time to the best of our knowledge. Over 80% of the initial TCP was degraded at optimum flow rate under an applied air pressure of about 0.7 bar or lower. This corresponds to degrading a substantial amount of the initial substrate in only 36 seconds residence time, which in a batch reaction take hours. This, in fact, demonstrates an energy efficient flow through system with potential large scale applications. Comparison of the stability of the enzyme in solution phase vs. immobilized on membrane phase showed a loss of some 65% of enzyme activity in the solution phase after 22 days, whereas the membrane-bound enzyme lost only a negligible percentage of activity in comparable time span. Finally, the membrane was exposed to rigorous cycles of TCP degradation trials to study its reusability. The primary results reveal a loss of only 14% of the initial activity after four cycles of use in a period of 25 days, demonstrating its potential to reuse. Regeneration of the functionalized membrane was also validated by dislodging the immobilized enzyme followed by immobilization of fresh enzyme on to the membrane.

Role of membrane pore polymerization conditions for pH responsive behavior, catalytic metal nanoparticle synthesis, and PCB degradation

“…The diameter and morphology of the membrane pores decreased substantially after the PAA polymerization reaction, becoming uniformly circular and smaller with an average pore size of 65 ± 7 nm (Fig. 3e); which conform with our earlier reported works [35,40]. The pores of the functionalized PVDF membrane reduced in size due to formation of PAA domain inside the pores.…”

“…Lab scale PVDF membranes were functionalized via an in-situ polymerization method, as reported before [31,35]. Before functionalization, membranes were soaked in methanol for 5–10 min to remove dirt, clean the pores and increase the hydrophilicity of the surface [36].…”

Synthesis of magnetic nanoparticles with an IDA or TED modified surface for purification and immobilization of poly-histidine tagged proteins

“…Protein and enzyme immobilization have extensive applications in the environment and biomedicine. [1][2][3][4] Current approaches for immobilizing enzymes include embedding, adsorption, crosslinking, covalent bonding. [5][6][7][8] For example, glucose sensitivity was greatly improved by using glucose oxidase (GOx) and horseradish peroxidase (HRP) co-embedded nanoowers.…”

Miniaturized systems for evaluating enzyme activity in polymeric membrane bioreactors

“…It is a complex aromatic polymer rich in phenolic compounds; enzyme‐based reactors that can oxidize these phenols and depolymerize lignin could provide a new route to sustainable biofuels and aromatic fine chemicals beyond conventional refineries . Research groups are looking at laccase enzymes for breaking down organic materials ; these enzymes can adhere to charged membrane surfaces and can also be engineered with binding sites such as his‐tag sequences to attach to metal‐ion coated synthetic membranes. Membrane‐immobilized enzymes that can break down lignin from woody and non‐woody plants are sought after for compact and room‐temperature energy extraction systems.…”