Selective synthesis of rebaudioside M2 through structure-guided engineering of glycosyltransferase UGT94D1.

Rebaudioside M2 (Reb M2), a novel steviol glycoside derivative, has limited industrial applications due to its low synthetic yield and selectivity. Herein, we identify UGT94D1 as a selective glycosyltransferase for rebaudioside D (Reb D), leading to the production of a mono ß-1,6-glycosylated derivative, Reb M2. A variant UGT94D1-F119I/D188P was developed through protein engineering. This mutant exhibited a 6.33-fold improvement in catalytic efficiency, and produced Reb M2 with 92% yield. Moreover, molecular dynamics simulations demonstrated that UGT94D1-F119I/D188P exhibited a shorter distance between the nucleophilic oxygen (OH6) of the substrate Reb D and uridine diphosphate glucose, along with an increased Ophosphate-C1-Oacceptor angle, thus improving the catalytic activity of the enzyme. Therefore, this study provides an efficient method for the selective synthesis of Reb M2 and paves the way for its applications in various fields.

A carbon ink for use in thin, conductive, non peelable, amphiphilic, antioxidant, and large-area current collector coating with enhanced lithium ion battery performance.

We reported that a stable carbon ink composed of conductive carbon materials (graphene and super P), binder (sodium carboxymethyl cellulose (CMC)), interface active agent (sodium dodecyl sulfate (SDS)), and metal coupling agent ((3-aminopropyl)triethoxysilane (APTES)) for using in coating conducting layer on cathode/anode current collector for LIBs. Graphene materials are obtained using a low-cost graphite material (KS 6) and processing it via a wet ball-milling to exfoliate single layers into the ink. The ink can be coated on the LIB current collector in a large area by a doctor blade to form a carbon layer of about 1 µm without overflow. Carbon-coated current collectors have amphiphilic properties, not peel off under extreme physical and chemical conditions, and resist oxidation under high temperature (200 °C) processing conditions. In addition, carbon-coated current collector are superior to the batteries using bare metal foil a current collectors in the LIB performance of graphite half-cell, graphite full-cell, LiFePO4 half-cell, and silicon-carbon full-cell. These results show that the carbon-coated metal foil can reduce the interface resistance with the active material and improves the adhesion of the active materials to the current collector, avoiding peeling off during charge/discharge process, thereby improving of LIBs performance. The developed method can produce high-quality, low-cost carbon material inks on a large scale through a simple and inexpensive process, and coat them evenly and finely on current collectors, making it possible to achieve efficient industrial and commercial perspectives for next-generation LIB-based current collectors.