Structural characterization, and in vitro hypoglycemic activity of a polysaccharide from the mushroom Cantharellus yunnanensis.

A polysaccharide CY-2 from C. yunnanensis was obtained through a process of consecutive water extraction, alcohol precipitation, and DEAE-52 fast-flow chromatography. CY-2, with an average molecular weight of 2.69 × 104 Da mainly consisted of glucose and mannose with a molar ratio of 33.5: 56.9. Infrared spectrum (IR), methylation analysis, and nuclear magnetic resonance (NMR) results revealed that CY-2 may have a backbone consisting of →6)-α-D-Manp-(1 â†’ 3)-ß-D-Glcp-(1→, and branch chain ß-D-Glcp-(1→. Meanwhile, CY-2 had a higher inhibition rate on α-glucosidase activity compared with other fractions (CY-0, CY-1, and CY-4) and was a mixed competitive inhibitor. In addition, CY-2 at the concentration of 10 µg/mL presented a superior power to improve glucose consumption and metabolism in HepG2 cells compared with metformin. Overall, these findings highlight the potential value of CY-2 as a hypoglycemic agent.

Structural characterization of pectic polysaccharides from Amaranth caudatus leaves and the promotion effect on hippocampal glucagon-like peptide-1 level.

In this study, decolorized pectic polysaccharides (D-ACLP) with molecular weight (Mw) distribution of 3483- 2,023,656 Da were prepared from Amaranth caudatus leaves. Purified polysaccharides (P-ACLP) with the Mw of 152,955 Da were further isolated from D-ACLP through gel filtration. The structure of P-ACLP was analyzed by 1D and 2D NMR spectra. P-ACLP were identified as rhamnogalacturonan-I (RG-I) containing dimeric arabinose side chains. The main chain of P-ACLP was composed of →4)-α-GalpA-(1→, →2)-ß-Rhap-(1→, →3)-ß-Galp-(1→ and →6)-ß-Galp-(1→. There was a branched chain of α-Araf-(1→2)-α-Araf-(1→ connected to the O-6 position of →3)-ß-Galp-(1→. The GalpA residues were partially methyl esterified at O-6 and acetylated at O-3. The 28-day consecutive gavage of D-ALCP (400 mg/kg) significantly elevated the hippocampal glucagon-like peptide-1 (GLP-1) levels in rats. The concentrations of butyric acid and total short chain fatty acids in the cecum contents also increased significantly. Moreover, D-ACLP could significantly increase the gut microbiota diversity and dramatically up-regulated the abundance of Actinobacteriota (phylum) and unclassified Oscillospiraceae (genus) in intestinal bacteria. Taking together, D-ACLP might promote the hippocampal GLP-1 level through the beneficial regulation of butyric acid-producing bacteria in gut microbiota. This study contributed to making full use of Amaranth caudatus leaves for cognitive dysfunction intervention in food industry.

Purification and characterization of a cellulase-free, thermostable endo-xylanase from Streptomyces griseorubens LH-3 and its use in biobleaching on eucalyptus kraft pulp.

Xylanase is an important enzyme involved in degrading xylan. In this study, an extracellular cellulase-free, thermostable endo-xylanase which was produced by Streptomyces griseorubens LH-3 with bagasse semi-cellulose as a carbon source was purified and characterized. The xylanase was purified 4-fold with a recovery yield of 21.6% by precipitation with 25-55% (NH4)2SO4, Mono Q ion exchange chromatography and sephacryl S-200 HR gel filtration chromatography. It appeared as a monomeric protein on SDS-PAGE gel and had an apparent molecular weight of 45.5 kDa with specific activity of 434 IU/mg. Using birchwood xylan as substrate, the maximum velocity (Vmax) and Michaelis-Menten constant (Km) were found to be 1.44 mg/ml and 2.05 µmol/min mg, respectively. The purified xylanase was active at pH 4.0-8.0 with an optimum pH of 5.0. It was stable at temperatures between 30°C and 50°C, exhibiting maximum activity at 60°C. Hg2+ and Al3+ inhibited the enzyme activity significantly. Enzymatic product analysis indicated that the enzyme was an endo-xylanase, whose hydrolysis products were mainly a series of short-chain xylooligosaccharides. Furthermore, it was used for biobleaching of eucalyptus kraft pulp, and results showed that this purified xylanase increased the brightness of the pulp by 14.5% and reduced the kappa number by 24.5%. All these industrially relevant characteristics made it had potential application in the pulp and paper industry as a biobleaching agent.