Cellulase Immobilization on Nanostructured Supports for Biomass Waste Processing

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

Microbial β-glucanases: production, properties, and engineering

Lignocellulosic biomass, which mainly consists of cellulose and hemicellulose, is the most abundant renewable biopolymer on earth. β-Glucanases are glycoside hydrolases (GHs) that hydrolyze β-glucan, one of the dominant components of the plant cell wall, into cello-oligosaccharides and glucose. Among them, endo-β-1,4-glucanase (EC 3.2.1.4), exo-glucanase/cellobiohydrolase (EC 3.2.1.91), and β-glucosidase (EC 3.2.1.21) play critical roles in the digestion of glucan-like substrates. β-Glucanases have attracted considerable interest within the scientific community due to their applications in the feed, food, and textile industries. In the past decade, there has been considerable progress in the discovery, production, and characterization of novel β-glucanases. Advances in the development of next-generation sequencing techniques, including metagenomics and metatranscriptomics, have unveiled novel β-glucanases isolated from the gastrointestinal microbiota. The study of β-glucanases is beneficial for research and development of commercial products. In this study, we review the classification, properties, and engineering of β-glucanases.

Co-Immobilization of Lactase and Glucose Isomerase on the Novel g-C3N4/CF Composite Carrier for Lactulose Production

The g-C₃N₄/CF composite carrier was prepared by ultrasound-assisted maceration and high-temperature calcination. The enzyme immobilization using the g-C₃N₄/CF as the novel carrier to immobilize lactase and glucose isomerase was enhanced for lactulose production. The carbon fiber (CF) was mixed with melamine powder in the mass ratio of 1:8. The g-C₃N₄/CF composite carrier was obtained by calcination at 550 °C for 3 h. After the analysis of characteristics, the g-C₃N₄/CF was successfully composited with the carbon nitride and CF, displaying the improvement of co-immobilization efficiency with the positive effects on the stability of the enzyme. The immobilization efficiency of the co-immobilized enzyme was 37% by the novel carrier of g-C₃N₄/CF, with the enzyme activity of 13.89 U g^-1 at 60 °C. The relative activities of co-immobilized enzymes maintained much more steadily at the wider pH and higher temperature than those of the free dual enzymes, respectively. In the multi-batches of lactulose production, the relative conversion rates in enzymes co-immobilized by the composite carrier were higher than that of the free enzymes during the first four batches, as well as maintaining about a 90% relative conversation rate after the sixth batch. This study provides a novel method for the application of g-C₃N₄/CF in the field of immobilizing enzymes for the production of lactulose.