Inhibitory effect of lignin on the hydrolysis of xylan by thermophilic and thermolabile GH11 xylanases

BACKGROUND: Enzymatic hydrolysis of lignocellulosic biomass into platform sugars can be enhanced by the addition of accessory enzymes, such as xylanases. Lignin from steam pretreated biomasses is known to inhibit enzymes by non-productively binding enzymes and limiting access to cellulose. The effect of enzymatically isolated lignin on the hydrolysis of xylan by four glycoside hydrolase (GH) family 11 xylanases was studied. Two xylanases from the mesophilic Trichoderma reesei, TrXyn1, TrXyn2, and two forms of a thermostable metagenomic xylanase Xyl40 were compared. RESULTS: Lignin isolated from steam pretreated spruce decreased the hydrolysis yields of xylan for all the xylanases at 40 and 50 °C. At elevated hydrolysis temperature of 50 °C, the least thermostable xylanase TrXyn1 was most inhibited by lignin and the most thermostable xylanase, the catalytic domain (CD) of Xyl40, was least inhibited by lignin. Enzyme activity and binding to lignin were studied after incubation of the xylanases with lignin for up to 24 h at 40 °C. All the studied xylanases bound to lignin, but the thermostable xylanases retained 22–39% of activity on the lignin surface for 24 h, whereas the mesophilic T. reesei xylanases become inactive. Removing of N-glycans from the catalytic domain of Xyl40 increased lignin inhibition in hydrolysis of xylan when compared to the glycosylated form. By comparing the 3D structures of these xylanases, features contributing to the increased thermal stability of Xyl40 were identified. CONCLUSIONS: High thermal stability of xylanases Xyl40 and Xyl40-CD enabled the enzymes to remain partially active on the lignin surface. N-glycosylation of the catalytic domain of Xyl40 increased the lignin tolerance of the enzyme. Thermostability of Xyl40 was most likely contributed by a disulphide bond and salt bridge in the N-terminal and α-helix regions. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13068-022-02148-4

Techniques and Issues in Multicast Security

Multicast networking support is becoming an increasingly important future technology area for both commercial and military distributed and group-based applications. Integrating a multicast security solution involves numerous engineering tradeoffs. The end goal of effective operational performance and scalability over a heterogeneous internetwork is of primary interest for widescale adoption and application of such a capability. Various techniques that have been proposed to support multicast security are discussed and their relative merits are explored

TECHNIQUES AND

Mdticast networking support is becoming an increasingly important future technology area for both commercial and military distributed and group-based applications. Integrating a multicast security solution involves numerous engineering tradeoffs. The end goal of effective operational performance and scalabili ~ over a heterogeneous internetwork is of prima ~ interest for widescale adoption and application ofsucha capabili~. Various techniques that have beenproposedto support multicast security are discussed and their relative merits are explored

A Survey of Multicast Security Issues and Architectures

This paper addresses issues relevant to implementing security for IP multicast networks. These issues are of importance to application developers wishing to implement security services for their multicast applications. The paper investigates the steps required to create a secure multicast session including issues of group membership and key distribution. A common simple criteria is established that can be used to evaluate multicast keying architectures. The criteria focuses on the efficiency and scalability of the keying solution. Using this criteria, several keying architectures are evaluated and compared to determine their strengths and weaknesses

MRD-Cl potential surfaces using balanced basis sets. IV. The H2 molecule and the H3 surface

The utility of midbond functions in molecular calculations was tested in two cases where the correct results are known: the H2 potential curve and the collinear H3 potential surface. For H2, a variety of basis sets both with and without bond functions was compared to the exact nonrelativistic potential curve of Kolos and Wolniewicz [J. Chem. Phys. 43, 2429 (1965)]. It was found that optimally balanced basis sets at two levels of quality were the double zeta single polarization plus sp bond function basis (BF1) and the triple zeta double polarization plus two sets of sp bond function basis (BF2). These gave bond dissociation energies De=4.7341 and 4.7368 eV, respectively (expt. 4.7477 eV). Four basis sets were tested for basis set super-position errors, which were found to be small relative to basis set incompleteness and therefore did not affect any conclusions regarding basis set balance. Basis sets BF1 and BF2 were used to construct potential surfaces for collinear H3, along with the corresponding basis sets DZ*P and TZ*PP which contain no bond functions. Barrier heights of 12.52, 10.37, 10.06, and 9.96 kcal/mol were obtained for basis sets DZ*P, TZ*PP, BF1, and BF2, respectively, compared to an estimated limiting value of 9.60 kcal/mol. Difference maps, force constants, and relative rms deviations show that the bond functions improve the surface shape as well as the barrier height

MRD Cl calculation of the first and second ionization potential of OH

Multireference Cl calculations are reported for OH(2Π). OH+ (3Σ-), and OH2+ (4Σ-) using several basis sets. Ionization potentials derived from the potential curves are compared to previous calculations and to experimental values. We show that the errors obtained from the calculations can be traced to the difficulty in obtaining an accurate treatment of the ionization energy of the oxygen atom. No experimental artifact needs to be invoked to explain the discrepancy with the experimental results