Ionic liquids (ILs) are innovative and effective solvents for pretreating lignocellulose biomasses because they bring about a noticeable increase in the enzymatic saccharification of these materials. However, the reported solid loadings in ILs of approximately 5.0 wt% reflect their large consumption per gram of biomass and hinder their use in biomass pretreatment. In the present study, a twin-screw extruder with high shearing force was used as a pretreatment reactor to process sugarcane bagasse at high loadings in the IL 1-ethyl-3-methylimidazolium acetate. This procedure allowed effective pretreatment of biomasses at loadings as high as 25 wt% for 8 min at 140 °C, resulting in glucose yields of more than 90% after 24 h of enzymatic saccharification of the pretreated material. This glucose yield was comparable to that of a 4.8 wt% bagasse loading that was pretreated for 120 min at 120 °C in a stirring reactor and enzymatically hydrolyzed under the same conditions. A higher bagasse loading, 50 wt%, also afforded a high glucose yield of 76.4%. Characterization of the pretreated materials by examining the surface morphology at the nanoscopic scale, measuring the specific surface area (SSA), and analyzing the degree of crystallinity showed that the use of the extruder as a pretreatment reactor significantly decreased the crystallinity and increased the SSA by more than 100-fold. In addition, the extrusion process can be conducted continuously and is appropriate for industrial-scale biomass processing, allowing higher reactant concentrations and throughputs, higher mixing rates, and more uniform products compared to batch processes.

This study presents data on the production, purification, and properties of a thermostable β-xylanase produced by an Aspergillus awamori 2B.361 U2/1 submerged culture using wheat bran as carbon source. Fractionation of the culture filtrate by membrane ultrafiltration followed by Sephacryl S-200 and Q-Sepharose chromatography allowed for the isolation of a homogeneous xylanase (PXII-1), which was 32.87 kDa according to MS analysis. The enzyme-specific activity towards soluble oat spelt xylan, which was found to be 490 IU/mg under optimum reaction conditions (50°C and pH 5.0–5.5), was 17-fold higher than that measured in the culture supernatant. Xylan reaction products were identified as xylobiose, xylotriose, and xylotetraose. K _m values (mg ml⁻¹) for soluble oat spelt and birchwood xylan were 11.8 and 9.45, respectively. Although PXII-1 showed 85% activity retention upon incubation at 50°C and pH 5.0 for 20 days, incubation at pH 7.0 resulted in 50% activity loss within 3 days. PXII-1 stability at pH 7.0 was improved in the presence of 20 mM cysteine, which allowed for 85% activity retention for 25 days. This study on the production in high yields of a remarkably thermostable xylanase is of significance due to the central role that this class of biocatalyst shares, along with cellulases, for the much needed enzymatic hydrolysis of biomass. Furthermore, stable xylanases are important for the manufacture of paper, animal feed, and xylooligosaccharides.

The production of xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 °C and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources; in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, β-xylosidase and ferulic acid esterase to a peak concentrations of 44,880; 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest β-glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of β-glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and β-xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.