A Possible Mechanism of Graphene Oxide to Enhance Thermostability of D-Psicose 3-Epimerase Revealed by Molecular Dynamics Simulations

Advances in the biosynthesis of D-allulose

D-allulose is a rare monosaccharide and a C-3 epimer of D-fructose. It has physiological functions, such as antihyperglycemic, obesity-preventing, neuroprotective, and reactive oxygen species (ROS) scavenging effects, making it an ideal sugar substitute. The synthesis methods for D-allulose include chemical synthesis and biosynthesis. Chemical synthesis requires strict reaction conditions and tends to produce byproducts. Biosynthesis is mainly an enzymatic process. Enzymatic catalysis for the conversion of starch or glycerol to D-allulose is performed mainly by enzymes such as isoamylase (IA), glucose isomerase (GI), D-allulose 3-epimerase (DPE), D-allulose-6-phosphate 3-epimerase (A6PE), D-allulose 6-phosphate phosphatase (A6PP), ribitol 2-dehydrogenase (RDH), glycerophosphate kinase (GK), glycerophosphate oxidase (GPO), and dihydroxyacetone phosphate (DHAP)-dependent aldolase. Biosynthesis is a more energy-efficient process, producing fewer harmful by-products and pollutants, and significantly reducing negative environmental impacts. Furthermore, the specific catalytic activity of enzymes facilitates the production of compounds of higher purity, thereby facilitating the isolation and purification of the products. It has thus become the main method for producing D-allulose. This article reviews the progress in research on the biosynthetic production of D-allulose, focusing on the enzymes involved and their enzymatic properties, and discusses the production prospects for D-allulose.

An Overview of Crosslinked Enzyme Aggregates: Concept of Development and Trends of Applications

Enzymes are commonly used as biocatalysts for various biological and chemical processes in industrial applications. However, their limited operational stability, catalytic efficiency, poor reusability, and high-cost hamper further industrial usage. Thus, crosslinked enzyme aggregates (CLEAs) are developed as a better enzyme immobilization tool to extend the enzymes' operational stability. This immobilization method is appealing because it is simpler due to the absence of ballast and permits the collective use of crude enzyme cocktails. CLEAs, so far, have been successfully developed using a variety of enzymes, viz., hydrolases, proteases, amidases, lipases, esterases, and oxidoreductase. Recent years have seen the emergence of novel strategies for preparing better CLEAs, which include the combi- and multi-CLEAs, magnetics CLEAs, and porous CLEAs for various industrial applications, viz., laundry detergents, organic synthesis, food industries, pharmaceutical applications, oils, and biodiesel production. To better understand the different strategies for CLEAs' development, this review explores these strategies and highlights the relevant concerns in designing innovative CLEAs. This article also details the challenges faced during CLEAs preparation and solutions for overcoming them. Finally, the trending strategies to improve the preparation of CLEAs alongside their industrial application trends are also discussed.

Enzyme immobilization studied through molecular dynamic simulations

In recent years, simulations have been used to great advantage to understand the structural and dynamic aspects of distinct enzyme immobilization strategies, as experimental techniques have limitations in establishing their impact at the molecular level. In this review, we discuss how molecular dynamic simulations have been employed to characterize the surface phenomenon in the enzyme immobilization procedure, in an attempt to decipher its impact on the enzyme features, such as activity and stability. In particular, computational studies on the immobilization of enzymes using i) nanoparticles, ii) self-assembled monolayers, iii) graphene and carbon nanotubes, and iv) other surfaces are covered. Importantly, this thorough literature survey reveals that, while simulations have been primarily performed to rationalize the molecular aspects of the immobilization event, their use to predict adequate protocols that can control its impact on the enzyme properties is, up to date, mostly missing.

Cross-linked cyclodextrin glucanotransferase aggregates from Bacillus lehensis G1 for cyclodextrin production: Molecular modeling, developmental, physicochemical, kinetic and thermodynamic properties

Type of cross-linking agents influence the stability and active cross-linked enzyme aggregates (CLEA) immobilization. The information of molecular interaction between enzyme-cross linker is not well explored thus screening wide numbers of cross-linker is crucial in CLEA development. This study combined the molecular modeling and experimental optimization to investigate the influences of different cross-linking agents in developing CLEA of cyclodextrin glucanotranferase G1 (CGTase G1) for cyclodextrins (CDs) synthesis. Seven types of cross-linkers were tested and CGTase G1 cross-linked with chitosan (CS-CGTG1-CLEA) displayed the highest activity recovery (84.6 ± 0.26%), aligning with its highest binding affinity, radius of gyration and flexibility through in-silico analysis towards CGTase G1. CS-CGTG1-CLEA was characterized and showed a longer half-life (30.06 ± 1.51 min) and retained a greater thermal stability (52.73 ± 0.93%) after 30 min incubation at optimal conditions compared to free enzyme (10.30 ± 1.34 min and 5.51 ± 2.10% respectively). CS-CGTG1-CLEA improved CDs production by 33% and yielded cumulative of 52.62 g/L CDs after five cycles for 2 h of reaction. This study reveals that abundant of hydroxyl group on chitosan interacted with CGTase G1 surface amino acid residues to form strong and stable CLEA thus can be a promising biocatalyst in CDs production.