Arabinoxylan source and xylanase specificity influence the production of oligosaccharides with prebiotic potential

Cereal arabinoxylans (AXs) are complex polysaccharides in terms of their pattern of arabinose and ferulic acid substitutions, which influence their properties in structural and nutritional applications. We have evaluated the influence of the molecular structure of three AXs from wheat and rye with distinct substitutions on the activity of β-xylanases from different glycosyl hydrolase families (GH 5_34, 8, 10 and 11). The arabinose and ferulic acid substitutions influence the accessibility of the xylanases, resulting in specific profiles of arabinoxylan-oligosaccharides (AXOS). The GH10 xylanase from Aspergillus aculeatus (AcXyn10A) and GH11 from Thermomyces lanuginosus (TlXyn11) showed the highest activity, producing larger amounts of small oligosaccharides in shorter time. The GH8 xylanase from Bacillus sp. (BXyn8) produced linear xylooligosaccharides and was most restricted by arabinose substitution, whereas GH5_34 from Gonapodya prolifera (GpXyn5_34) required arabinose substitution and produced longer (A)XOS substituted on the reducing end. The complementary substrate specificity of BXyn8 and GpXyn5_34 revealed how arabinoses were distributed along the xylan backbones. This study demonstrates that AX source and xylanase specificity influence the production of oligosaccharides with specific structures, which in turn impacts the growth of specific bacteria (Bacteroides ovatus and Bifidobacterium adolescentis) and the production of beneficial metabolites (short-chain fatty acids)

Cloning of a GH5 endoglucanase from genus <i>Penicillium</i> and its binding to different lignins

The <i>cel5C</i> gene, coding for an endoglucanase (Cel5C) of <i>Penicillium brasilianum</i> was cloned and heterologously expressed in <i>Aspergillus oryzae</i>. This is only the second GH5 EG from the genus <i>Penicillium</i> reported in the CAZy database. The promoter region of the gene has putative binding sites for both the carbon catabolite repressor CreA and the activator XlnR. The pH optimum of Cel5C was found to be 4.0 and the temperature optimum was 70°C. At a typical temperature for lignocellulose hydrolysis Cel5C retained full residual activity after 20 h of incubation at pH 5.0 and 6.0. Adsorption to Avicel and steam pretreated spruce, was found to follow the Langmuir isotherm, and the maximum adsorption was similar for both substrates, 40 and 49 mg/g, respectively. The affinity for Avicel was 10 times higher than for steam pretreated spruce, 0.040 and 0.0035 L/mg, respectively. Non-productive binding of cellulolytic enzymes to lignin is an important obstacle to overcome for commercial biomass to ethanol production. Therefore, the adsorption on residual lignin produced from various biomass samples was investigated. Both substrate and pretreatment conditions resulted in different adsorptions of Cel5C to residual lignin

Cloning of a GH5 endoglucanase from genus Penicillium and its binding to different lignins

The cel5C gene, coding for an endoglucanase (Cel5C) of Penicillium brasilianum was cloned and heterologously expressed in Aspergillus oryzae. This is only the second GH5 EG from the genus Penicillium reported in the CAZy database. The promoter region of the gene has putative binding sites for both the carbon catabolite repressor CreA and the activator XlnR. The pH optimum of Cel5C was found to be 4.0 and the temperature optimum was 70\ub0C. At a typical temperature for lignocellulose hydrolysis Cel5C retained full residual activity after 20 h of incubation at pH 5.0 and 6.0. Adsorption to Avicel and steam pretreated spruce, was found to follow the Langmuir isotherm, and the maximum adsorption was similar for both substrates, 40 and 49 mg/g, respectively. The affinity for Avicel was 10 times higher than for steam pretreated spruce, 0.040 and 0.0035 L/mg, respectively. Non-productive binding of cellulolytic enzymes to lignin is an important obstacle to overcome for commercial biomass to ethanol production. Therefore, the adsorption on residual lignin produced from various biomass samples was investigated. Both substrate and pretreatment conditions resulted in different adsorptions of Cel5C to residual lignin