Separation and characterization of biomass components (cellulose, hemicellulose, and lignin) from corn stalk

Representative hemicellulose, milled wood lignin (MWL), and cellulose were directly separated from corn stalk, and their main chemical content was determined using NREL methods. The chemical elements, chemical groups, and molecular structure of corn stalk biomass components (hemicellulose, MWL, and cellulose) were analyzed by elemental analysis, Fourier transform infrared, and nuclear magnetic resonance spectroscopy analyses．The results showed that the purity of the biomass components separated from corn stalk was high, the degree of damage was relatively small, and their own structural characteristics were relatively intact. The hemicellulose that was separated from corn stalk was mainly composed of L-arabino-β-(1→4)-D-glucuronoxylan units. There were also sugar residues attached to the main chain in the form of side chains, such as D-glucopyranose, galactose, glucuronic acid, and galacturonic acid. The isolated cellulose consisted of glucosyl linked by β-(1→4)-glucosidic bond. The MWL separated from corn stalk has a GSH-type of β-O-4 structure, and the contents were as follows, in order of more to less: guaiacyl (G), p-hydroxyphenyl (H), and syringyl (S) units. Biomass components with high purity were separated from corn stalk, and their respective structure and composition were understood, which provides a foundation for the subsequent high-value utilization of corn stalk.

Crystal structure of glycosyltrehalose synthase fromSulfolobus shibataeDSM5389

Glycosyltrehalose synthase (GTSase) converts the glucosidic bond between the last two glucose residues of amylose from an α-1,4 bond to an α-1,1 bond, generating a nonreducing glycosyl trehaloside, in the first step of the biosynthesis of trehalose. To better understand the structural basis of the catalytic mechanism, the crystal structure of GTSase from the hyperthermophilic archaeonSulfolobus shibataeDSM5389 (5389-GTSase) has been determined to 2.4 Å resolution by X-ray crystallography. The structure of 5389-GTSase can be divided into five domains. The central domain contains the (β/α)8-barrel fold that is conserved as the catalytic domain in the α-amylase family. Three invariant catalytic carboxylic amino acids in the α-amylase family are also found in GTSase at positions Asp241, Glu269 and Asp460 in the catalytic domain. The shape of the catalytic cavity and the pocket size at the bottom of the cavity correspond to the intramolecular transglycosylation mechanism proposed from previous enzymatic studies.

A two-step O- to C-glycosidic bond rearrangement using complementary glycosyltransferase activities

A 2′-O- to 3′-C-glucosidic bond rearrangement on the flavonoid-like aglycon phloretin was catalysed with perfect atom economy by coupled uridine 5′-diphosphate dependent O- and C-glycosyltransferase activities.

Chemical Analysis and Antioxidant Activities In Vitro of Polysaccharide Extracted from Corn Silk

Corn silk polysaccharide (CSP) was investigated for the treatment of different kinds of diseases. In order to characterize the chemical properties and antioxidant activities of CSP, the CSP was isolated from corn silk and purified by DE-52 cellulose column chromatography. Four components were separated, and the highest one named CSP-A. The CSP-A was characterized by FTIR and the monosaccharide components were analyzed by HPLC. The FTIR spectra indicated that CSP-A was characteristic of β-glucosidic bond and α-glycosidic bond. The CSP-A mainly comprised of glucose, galactose, arabinose, mannose, rhamnose. The antioxidant activities of CSP were determined by hydroxyl radical (•OH) and DPPH radicals scavenging assays. When the concentration of CSP was 10mg/mL, the scavenging capacity of •OH and DPPH could reach to 40% and 48%, respectively.