Cellulase Immobilization on Nanostructured Supports for Biomass Waste Processing

Nanobiocatalysts, i.e., enzymes immobilized on nanostructured supports, received considerable attention because they are potential remedies to overcome shortcomings of traditional biocatalysts, such as low efficiency of mass transfer, instability during catalytic reactions, and possible deactivation. In this short review, we will analyze major aspects of immobilization of cellulase—an enzyme for cellulosic biomass waste processing—on nanostructured supports. Such supports provide high surface areas, increased enzyme loading, and a beneficial environment to enhance cellulase performance and its stability, leading to nanobiocatalysts for obtaining biofuels and value-added chemicals. Here, we will discuss such nanostructured supports as carbon nanotubes, polymer nanoparticles (NPs), nanohydrogels, nanofibers, silica NPs, hierarchical porous materials, magnetic NPs and their nanohybrids, based on publications of the last five years. The use of magnetic NPs is especially favorable due to easy separation and the nanobiocatalyst recovery for a repeated use. This review will discuss methods for cellulase immobilization, morphology of nanostructured supports, multienzyme systems as well as factors influencing the enzyme activity to achieve the highest conversion of cellulosic biowaste into fermentable sugars. We believe this review will allow for an enhanced understanding of such nanobiocatalysts and processes, allowing for the best solutions to major problems of sustainable biorefinery

Insights into Sustainable Glucose Oxidation Using Magnetically Recoverable Biocatalysts

Here, we developed magnetically recoverable biocatalysts for enzymatic oxidation of d-glucose to d-gluconic acid with high product yields. The catalyst support is based on nanoparticle clusters (NPCs) composed of magnetite particles and coated with the amino terminated silica layer to facilitate further functionalization. It involves the attachment of the glutaraldehyde linker followed by the covalent attachment of glucose oxidase (GOx) via its amino groups. It was established that the NPCs with a diameter of ∼430 nm attach 33% more GOx molecules than NPCs with a diameter of ∼285 nm, although the surface area of the former is lower than that of the latter. At the same time, the biocatalyst based on the smaller NPCs shows higher relative activity of 94% than that (87%) of the biocatalyst based on the larger NPCs, both at 50 °C and pH 7 (optimal reaction conditions). This surprising result has been explained by a combination of two major factors such as GOx crowding on the support surface which should prevent denaturation (similar to the enzyme behavior in cells) and the enzyme mobility which should be preserved upon immobilization. Apparently, for the biocatalyst based on 285 nm NPCs, the lower GOx crowding is compensated by its higher mobility. The high stability of these GOx based biocatalysts in 10 consecutive reactions as well as facile magnetic recovery combined with excellent catalytic activity in “tolerant” pH range make this biocatalyst design promising for other types of enzymatic catalysts

Immobilized glucose oxidase on magnetic silica and alumina: Beyond magnetic separation

Here we report immobilization of glucose oxidase (GOx) on magnetic silica (Fe3O4-SiO2) and alumina (Fe3O4-Al2O3) functionalized with amino groups using glutaraldehyde as a linker. Magnetic support based biocatalysts demonstrate high catalytic activity in d-glucose oxidation to D-gluconic acid at pH 5–7.5 and temperature of 30–50 °C with the best activities of 95% and 91% for magnetic silica and alumina, respectively. A comparison of magnetic and non-magnetic alumina and silica shows a significant enhancement of the relative catalytic activity for magnetic supports, while the silica based biocatalysts show a higher activity than the biocatalysts based on alumina. A noticeably higher activity of GOx immobilized on magnetic supports is explained by synergy of the GOx inherent activity and enzyme-like activity of iron oxide nanoparticles, while the enhancement with silica based catalysts is most likely due to a larger pore size and stronger Brønsted acid sites. Excellent relative activity of Fe3O4-SiO2-GOx (95% of native GOx) in a tolerant pH and temperature range as well as high stability in a repeated use (6% relative activity loss after five catalytic cycles) makes this catalyst promising for practical applications

Influence of the Mesoporous Polymer Matrix Nature on the Formation of Catalytically Active Ruthenium Nanoparticles

This paper reports on ruthenium nanoparticles formation and stabilization by hypercrosslinked poly-styrene and the catalytic properties of the nanocomposites obtained. Hypercrosslinked polystyrene with functional groups and without them was used. The nanocomposites were characterized using low-temperature nitrogen physisorption, X-ray photoelectron spectroscopy and transmission electron mi-croscopy. It is established that the tertiary amine group of the support influences both formation of ru-thenium nanoparticles, and their catalytic properties in the selective hydrogenation of D-glucose. Copyright © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Insights into Sustainable Glucose Oxidation Using Magnetically Recoverable Biocatalysts

Here, we developed magnetically recoverable biocatalysts for enzymatic oxidation of d-glucose to d-gluconic acid with high product yields. The catalyst support is based on nanoparticle clusters (NPCs) composed of magnetite particles and coated with the amino terminated silica layer to facilitate further functionalization. It involves the attachment of the glutaraldehyde linker followed by the covalent attachment of glucose oxidase (GOx) via its amino groups. It was established that the NPCs with a diameter of ∼430 nm attach 33% more GOx molecules than NPCs with a diameter of ∼285 nm, although the surface area of the former is lower than that of the latter. At the same time, the biocatalyst based on the smaller NPCs shows higher relative activity of 94% than that (87%) of the biocatalyst based on the larger NPCs, both at 50 °C and pH 7 (optimal reaction conditions). This surprising result has been explained by a combination of two major factors such as GOx crowding on the support surface which should prevent denaturation (similar to the enzyme behavior in cells) and the enzyme mobility which should be preserved upon immobilization. Apparently, for the biocatalyst based on 285 nm NPCs, the lower GOx crowding is compensated by its higher mobility. The high stability of these GOx based biocatalysts in 10 consecutive reactions as well as facile magnetic recovery combined with excellent catalytic activity in “tolerant” pH range make this biocatalyst design promising for other types of enzymatic catalysts