Enzymatic production of xylooligosaccharides from corn cobs: Assessment of two different pretreatment strategies.

Corn cobs (CCs) are abundant xylan-rich agricultural wastes. Here, we compared CCs XOS yields obtained via two different pretreatment routs, alkali and hydrothermal, using a set of recombinant endo- and exo-acting enzymes from GH10 and GH11 families, which have different restrictions for xylan substitutions. Furthermore, impacts of the pretreatments on chemical composition and physical structure of the CCs samples were evaluated. We demonstrated that alkali pretreatment route rendered 59 mg of XOS per gram of initial biomass, while an overall XOS yield of 115 mg/g was achieved via hydrothermal pretreatment using a combination of GH10 and GH11 enzymes. These results hold a promise of ecologically sustainable enzymatic valorization of CCs via "green" and sustainable XOS production.

Trimetallic Nanoalloy of NiFeCo Embedded in Phosphidated Nitrogen Doped Carbon Catalyst for Efficient Electro-Oxidation of Kraft Lignin.

Recently, electro-oxidation of kraft lignin has been reported as a prominent electrochemical reaction to generate hydrogen at lower overpotential in alkaline water electrolysis. However, this reaction is highly limited by the low performance of existing electrocatalysts. Herein, we report a novel yet effective catalyst that comprises nonprecious trimetallic (Ni, Fe, and Co) nanoalloy as a core in a phosphidated nitrogen-doped carbon shell (referred to as sample P-NiFeCo/NC) for efficient electro-oxidation of kraft lignin at different temperatures in alkaline medium. The as-synthesized catalyst electro-oxidizes lignin only at 0.2 V versus Hg/HgO, which is almost three times less positive potential than in the conventional oxygen evolution reaction (0.59 V versus Hg/HgO) at 6.4 mA/cm2 in 1 M KOH. The catalyst demonstrates a turnover frequency (TOF) three to five times greater in lignin containing 1 M KOH than that of pure 1 M KOH. More importantly, the catalyst P-NiFeCo/NC shows theoretical hydrogen production of about 0.37 µmoles/min in the presence of lignin, much higher than that in pure 1 M KOH (0.0078 µ moles/min). Thus, this work verifies the benefit of the NiFeCo nanoalloy incorporated in carbon matrix, providing the way to realize a highly active catalyst for the electro-oxidation of kraft lignin.

Delignification of sugarcane bagasse using glycerol-water mixtures to produce pulps for saccharification.

This paper describes the organosolv delignification of depithed bagasse using glycerol-water mixtures without a catalyst. The experiments were performed using two separate experimental designs. In the first experiment, two temperatures (150 and 190°C), two time periods (60 and 240 min) and two glycerol contents (20% and 80%, v/v) were used. In the second experiment, which was a central composite design, the glycerol content was maintained at 80%, and a range of temperatures (141.7-198.3°C) and time (23-277 min) was used. The best result, obtained with a glycerol content of 80%, a reaction time of 150 min and a temperature of 198.3°C, produced pulps with 54.4% pulp yield, 7.75% residual lignin, 81.4% delignification and 13.7% polyose content. The results showed that high contents of glycerol tend to produce pulps with higher delignification and higher polyoses content in relation to the pulps obtained from low glycerol content reactions. In addition, the proposed method shows potential as a pretreatment for cellulose saccharification.

Monodisperse lignin fractions as standards in size-exclusion analysis: comparison with polystyrene standards.

The difficulty of preparing monodisperse lignin fractions on a large scale is a limiting factor in many applications. The present paper addresses this problem by examining the properties and size-exclusion behavior of lignin isolated by the acetosolv pulping process from post-extraction crushed sugarcane bagasse. The isolated lignin was subjected to a solvent pretreatment, followed by preparative gel permeation chromatography fractionation. The fractions were analyzed by high-performance size-exclusion chromatography (HPSEC) and these samples showed a great decrease in polydispersity, compared to the original acetosolv lignin. Several fractions of very low polydispersity, close to unity, were employed as calibration curve standards in HPSEC analysis. This original analytical approach allowed calibration with these lignin fractions to be compared with the polystyrene standards that are universally employed for lignin molecular mass determination. This led to a noteworthy result, namely that the lignin fractions and polystyrene standards showed very similar behavior over a large range of molecular masses in a typical HPSEC analysis of acetosolv lignin.

Surface esterification of cellulose fibers: characterization by DRIFT and contact angle measurements.

The surface chemical modification of microcrystalline cellulose and cellulose fibers obtained from different sugar cane bagasse pulping processes, viz. Kraft, organosolv ethanol/water and organosolv/supercritical carbon dioxide, were studied in heterogeneous conditions using modest amounts of octadecanoyl and dodecanoyl chloride. The ensuing surfaces acquired a non-polar character, suitable for incorporating these fibers as reinforcing agents in composite materials based on polymeric matrices. The success of these chemical modifications was assessed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and contact angle measurements. In particular, the dynamic and equilibrium contact angle measurements, before and after the treatments, revealed that the value of the polar component (gamma(s)p) of the surface energy had decreased very considerably following the modification.