Enzyme Catalytic Efficiency: A Function of Bio–Nano Interface Reactions

Abstract

Biocatalyst immobilization onto carbon-based nanosupports has been implemented in a variety of applications ranging from biosensing to biotransformation and from decontamination to energy storage. However, retaining enzyme functionality at carbon-based nanosupports was challenged by the non-specific attachment of the enzyme as well as by the enzyme-enzyme interactions at this interface shown to lead to loss of enzyme activity. Herein, we present a systematic study of the interplay reactions that take place upon immobilization of three pure enzymes namely soybean peroxidase, chloroperoxidase, and glucose oxidase at carbon-based nanosupport interfaces. The immobilization conditions involved both single and multipoint single-type enzyme attachment onto single and multi-walled carbon nanotubes and graphene oxide nanomaterials with properties determined by Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Our analysis showed that the different surface properties of the enzymes as determined by their molecular mapping and size work synergistically with the carbon-based nanosupports physico-chemical properties (i.e., surface chemistry, charge and aspect ratios) to influence enzyme catalytic behavior and activity at nanointerfaces. Knowledge gained from these studies can be used to optimize enzyme-nanosupport symbiotic reactions to provide robust enzyme-based systems with optimum functionality to be used for fermentation, biosensors, or biofuel applications.

Increasing the activity of immobilized enzymes with nanoparticle conjugation

“…NP morphology can play a key role in impacting enzymatic enhancement as well. Since NPs/nanotubes maintain higher radii of curvature due to their smaller diameters, these materials allow for increased center-tocenter distances between adjacent immobilized enzymes while limiting unfavorable protein-to-protein interactions [28]. Furthermore, enzyme orientation can be controlled by careful manipulation of the enzyme attachment chemistry, allowing for strategic orientation of the substrate binding pocket of the immobilized enzyme away from the NP surface and toward incident substrate [29 ].…”

Emerging Enzyme-Based Technologies for Wastewater Treatment

“…Immobilization onto nanosupports such as nanotubular aluminosilicate (71), graphene oxide (72), carbon nanotubes (73)(74)(75), graphene oxide sheets (74), nanodiamonds (76), and metal-oxide particles (77), was achieved either through physical or chemical means or through encapsulation into a gel (78) or membrane (79,80). Optimization of the immobilization conditions at any of these nanosupport interfaces involved controlling the enzyme interactions with the nanosupport or encapsulator (with or without a linker) (74) to preserve its functionality and catalytic behavior.…”

“…Optimization of the immobilization conditions at any of these nanosupport interfaces involved controlling the enzyme interactions with the nanosupport or encapsulator (with or without a linker) (74) to preserve its functionality and catalytic behavior. Typically, the immobilization interfaces could lead to non-specific interactions with the enzymes that could change its structure and conformation and decrease its catalytic activity (74). Previous studies have shown that additionally, protein-protein interactions (74,81) at such nanosupport interfaces could also lead to enzyme loss of activity (82).…”

“…For physical immobilization that relies primarily on nonspecific, hydrophobic interactions between enzyme and the nanosupport (77), it was observed that enzyme loadings (amount of enzyme/ amount of the support), activities and catalytic efficiencies (both relative to free enzyme in solution) are somewhat variable due to the inherent non-specificity of the interactions or the non-uniformity of enzyme loading (74). Complementary, for covalent immobilization that uses chemical reactions to form a covalent bond between the nanosupport and the enzyme (i.e., through a zero EDC/NHS chemistry between carboxylic acids and amines (73) or through the glutaraldehyde chemistry involving an interaction between amines and carbonyl groups) (83), it was shown that the chemical groups of the enzyme can be manipulated to interact with the functional groups of the nanosupport (83) with a variety of support functionalizations influencing the immobilization efficiency as well as its "initiator" (e.g., carboxylic acid (73), hydroxyl (76), amine (76), or carbonyl (76) respectively).…”

Hybrid nanocomposites with enhanced visible light photocatalytic ability for next generation of clean energy systems

“…[11,12] Specifically, studies aiming to improve TiO2 reactivity under visible light irradiation proposed introducing suitable heteroatoms onto its structure [13,14] and/or narrowing its band-gap. [15] However, such heteroatoms inserts need special technologies processing (e.g., sputtering, [16] ion implantation, [17] thermal treatments, [18] and others), are high energy cost and largely inefficient when yield is desired, thus with limited large-scale consumer and industrial implementation. Further, photocatalysis efficiency of the heteroatoms modified semiconductor materials may not be significantly improved when compared to their starting counterpart.…”