Improved secretory expression and characterization of thermostable xylanase and ß-xylosidase from Pseudothermotoga thermarum and their application in synergistic degradation of lignocellulose.

Xylanase and ß-xylosidase are the key enzymes for hemicellulose hydrolysis. To further improve hydrolysis efficacy, high temperature hydrolysis with thermostable hemicellulases showed promise. In this study, thermostable xylanase (Xyn) and ß-xylosidase (XynB) genes from Pseudothermotoga thermarum were cloned and secretory expressed in Bacillu subtilis. Compared with Escherichia coli expression host, B. subtilis resulted in a 1.5 time increase of enzymatic activity for both recombinant enzymes. The optimal temperature and pH were 95°C and 6.5 for Xyn, and 95°C and 6.0 for XynB. Thermostability of both recombinant enzymes was observed between the temperature range of 75-85°C. Molecular docking analysis through AutoDock showed the involvement of Glu525, Asn526, Trp774 and Arg784 in Xyn-ligand interaction, and Val237, Lys238, Val761 and Asn76 in XynB-ligand interaction, respectively. The recombinant Xyn and XynB exhibited synergistic hydrolysis of beechwood xylan and pretreated lignocellulose, where Xyn and XynB pre-hydrolysis achieved a better improvement of pretreated lignocellulose hydrolysis by commercial cellulase. The observed stability of the enzymes at high temperature and the synergistic effect on lignocellulosic substrates suggested possible application of these enzymes in the field of saccharification process.

Electrochemical annulation of 1,2,3-benzotriazinones with alkynes to access isoquinolin-1(2H)-ones.

An eco-friendly approach for electrochemical radical cascade annulation of 1,2,3-benzotriazinones with alkynes is described. Under catalyst-free and external reductant-free electrolysis conditions, a range of isoquinolin-1(2H)-ones were obtained in moderate to good yields. Cyclic voltammetry and control studies suggest that the reaction proceeds via a radical pathway. Furthermore, this approach could be easily scaled up.

Cobalt(III)-Catalyzed Fast and Solvent-Free C-H Allylation of Indoles Using Mechanochemistry.

Mechanochemical conditions have been applied to a highly efficient cobalt(III)-catalyzed C-H bond activation for the first time. In a subsequent step to the olefin insertion and ß-oxygen elimination, N-pyrimidinylindoles were allylated with vinylethylene carbonates in the absence of organic solvent under high-speed ball-milling condition. As the reaction afforded the desired products in up to 98% yields within a short time, this method constitutes an environmentally friendly and powerful alternative to the common solution-based approaches.