GDP-l-fucose, the key substrate for fucosyloligosaccharide biosynthesis, has been synthesized via a de novo pathway in bacteria. In the present study, genes for GDP-l-fucose biosynthesis were cloned into the expression vector pET-28a (+) to construct five E. coli strains, with recombinant enzymes being purified by using Ni–NTA chromatography. Following optimization of the 3-step reaction, Glk, ManB and ManC were added to the reaction mixture, after which Gmd and WcaG were added to overcome feedback inhibition from the end-product to produce GDP-l-fucose at 178.6 mg/l, with a yield of 14.1%. Our studies provide the basis for using cell-free enzyme production of GDP-l-fucose.

We extracted, purified, and characterized three neutral and three acidic polysaccharides from the roots, stems, and leaves of Aralia continentalis Kitigawa. The results of the analysis of monosaccharide composition indicated that the polysaccharides from the roots and stems were more similar to each other than they were to the polysaccharides from the leaves. The in vitro antioxidant results demonstrated that the acidic polysaccharides had stronger antioxidant activity than the neutral fractions. Therefore, we investigated the primary purified acidic polysaccharide fractions (WACP(R)-A-c, WACP(S)-A-c, and WACP(L)-A-d) by NMR and enzymatic analysis. The structural analytical results indicated that WACP(R)-A-c contained homogalacturonan (HG); WACP(S)-A-c contained HG and rhamnogalacturonan II (RG-II), and WACP(L)-A-d contained HG, RG-II, and rhamnogalacturonan I (RG-I) domains. Our findings offer insights into the screening of natural polysaccharide-based antioxidants and provide a theoretical basis for the application of A. continentalis.

Black soybean hull, as main by-production in black bean processing, has significant biological activity. In this study, the polysaccharide from black soybean hull (BSPS-H) was obtained by enzymatic hydrolysis, the yield was 5.3%, and its chemical composition and structural composition were further studied. The results shown that BSPS-H was mainly composed of Mannose, Galactose, and Glucose (molar ratio = 48.1: 29.7: 15.8), and might be existed in the form of pyran ring in α/β-linkage type. The anti-oxidant activity shown that BSPS-H had a certain capacity of anti-oxidation in a concentration-dependent manner. Among them, it has the best scavenging effect on DPPH free radicals. When the polysaccharide concentration was 10 mg/ml, the scavenging rate reached 94.37%. The results of anti-fatigue effect indicated that BSPS-H could prolong the duration of exhaustive swimming in mice, increased the contents of liver glycogen, reduced the content of blood urea nitrogen (BUN), enhanced the activity of lactate dehydrogenase (LDH) and reduced the accumulation of lactic acid (LA). This study provides a fundamental basis for the development and use of BSPS-H in medicine and functional foods. Graphical Abstract

Paenibacillus polymyxa exhibits remarkable hemicellulolytic activity. In the present study, 13 hemicellulose-degrading enzymes were identified from the secreted proteome of P. polymyxa KF-1 by liquid chromatography-tandem mass spectrometry analysis. α-L-arabinofuranosidase is an important member of hemicellulose-degrading enzymes. A novel α-L-arabinofuranosidase (PpAbf51b), belonging to glycoside hydrolase family 51, was identified from P. polymyxa. Recombinant PpAbf51b was produced in Escherichia coli BL21 (DE3) and was found to be a tetramer using gel filtration chromatography. PpAbf51b hydrolyzed neutral arabinose-containing polysaccharides, including sugar beet arabinan, linear-1,5-α-L-arabinan, and wheat arabinoxylan, with L-arabinose as the main product. The products from hydrolysis indicate that PpAbf51b functions as an exo-α-L-arabinofuranosidase. Combining PpAbf51b and Trichoderma longibrachiatum endo-1,4-xylanase produced significant synergistic effects for the degradation of wheat arabinoxylan. The α-L-arabinofuranosidase identified from the secretome of P. polymyxa KF-1 is potentially suitable for application in biotechnological industries.