Impact of bagasse lignin-carbohydrate complexes structural changes on cellulase adsorption behavior.

Pretreatment technology has attracted much attention as an effective method for the conversion of sugarcane bagasse into biochemicals. However, residual lignin-carbohydrate complexes (LCC) can negatively impact the subsequent enzymatic hydrolysis of bagasse. In this work, the changes in bagasse LCC after pretreatment with hot water and dilute acid were characterized by component analysis, 13C NMR and 1H-13C HSQC NMR to reveal the correlation between LCC structure and cellulase adsorption. A real-time dynamic model of LCC affecting adsorption of cellulase was constructed using a quartz crystal microbalance (QCM-D). The QCM-D results demonstrated that cellulase exhibited different adsorption characteristics on different LCCs. For example, the maximum adsorption capacities for cellulase onto the raw material LCC (RW-LCC), hot water pretreated LCC (LHW-LCC), and dilute acid pretreated LCC (AP-LCC) at 4 °C were 29.0 ng/cm2, 94.9 ng/cm2 and 129.8 ng/cm2, respectively. In addition, the adsorption rate constants for cellulase on RM-LCC, LHW-LCC and AP-LCC at 4 °C were 0.09, 0.14 and 0.19, respectively.

Solar light induced synthesis of silver nanoparticles by using lignin as a reductant, and their application to ultrasensitive spectrophotometric determination of mercury(II).

Lignin nanoparticles (LNPs) were employed as the reducing and stabilizing agent in the preparation of silver nanoparticles (Ag NPs) from silver nitrate under solar light. The Ag NPs were characterized by spectrophotometry, TEM, HRTEM, element mapping, XRD and XPS. The formation of Ag NPs and the structural changes of lignin during the reaction was monitored by analysis via 31P NMR, 1H NMR and 13C NMR. The Ag NPs have uniform shape and an average size of ~14 nm. They were loaded onto the surface of LNPs and entangled in lignin. The resulting Ag NP-LNP suspension displays an ultrasensitive and selective optical response to Hg (II) in giving a color change from yellow to colorless. The assay was performed by spectrophotometry at 450 nm. The analytically useful range extends from 5 nM to 100 nM of Hg (II), and the limit of detection is 1.4 nM in deionized water and 1.8 nM in spiked tap water. This is lower than the threshold level (10 nM) in drinking water specified by the US Environmental Protection Agency. Graphical abstract Schematic representation of the solar light induced synthesis of sliver nanoparticles (Ag NPs) by lignin nanoparticles (LNPs) and their application to colorimetric determination of Hg2+.

How Pseudo-lignin Is Generated during Dilute Sulfuric Acid Pretreatment.

Pseudo-lignin is generated from lignocellulose biomass during pretreatment with dilute sulfuric acid and has a significant inhibitory effect on cellulase. However, the mechanism of pseudo-lignin generation remains unclear. The following main points have been addressed to help elucidate the pseudo-lignin generation pathway. Cellulose and xylan were pretreated with sulfuric acid at different concentrations; aliquots were periodically collected; and the changes in the byproducts of the prehydrolysate were quantified. Milled wood lignin (MWL) mixed with cellulose and xylan was pretreated to evaluate the impact of lignin on pseudo-lignin generation. Furfural, 5-hydroxymethylfurfural, and MWL were pretreated as model compounds to investigate pseudo-lignin generation. The result indicated that the increasing acid concentration significantly promoted the generation of pseudo-lignin. When the acid concentration was increased from 0 to 1.00 wt %, pseudo-lignin was increased from 1.36 to 4.05 g. In addition, lignin promoted the pseudo-lignin generation through the condensation between lignin and the generated intermediates.

Fe3O4Nanoparticles Loaded on Lignin Nanoparticles Applied as a Peroxidase Mimic for the Sensitively Colorimetric Detection of H2O2.

Lignin is the second largest naturally renewable resource and is primarily a by-product of the pulp and paper industry; however, its inefficient use presents a challenge. In this work, Fe3O4 nanoparticles loaded on lignin nanoparticles (Fe3O4@LNPs) were prepared by the self-assembly method and it possessed an enhanced peroxidase-like activity. Fe3O4@LNPs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue color, was observable by the naked eye. Under the optimal conditions, Fe3O4@LNPs showed the ability of sensitive colorimetric detection of H2O2within a range of 5⁻100 µM and the limit of detection was 2 µM. The high catalytic activity of Fe3O4@LNPs allows its prospective use in a wide variety of applications, including clinical diagnosis, food safety, and environmental monitoring.

Improving the homogeneity of sugarcane bagasse kraft lignin through sequential solvents.

The heterogeneous features of lignin, especially the wide distribution of its molecular weight, limit its high value-added application. To improve the homogeneity of lignin, sugarcane bagasse kraft lignin (KL) dissolved in methanol/acetone (7 : 3, v/v) was successively fractionated into four fractions (i.e.., F1, F2, F3, and F4) with various organic solvents of decreasing dissolving capacity (i.e.., ethyl acetate, ethyl acetate/petroleum ether 1 : 1 v/v, and petroleum ether). The yields of the four fractions (F1, F2, F3, and F4) were 59.6, 28.4, 10.8, and 1.2% that of KL, respectively. Gel permeation chromatography (GPC) analysis indicated the molecular weight of each fraction decreased from F1 to F4. All fractions had a lower polydispersity than KL. KL and the fractions were comprehensively characterized by chemical composition analysis, elemental composition analysis (EA), methoxyl group analysis, Fourier transform infrared spectroscopy (FT-IR), nitrobenzene oxidation analysis (NBO), and nuclear magnetic resonance (NMR) including 31P and 1H-13C HSQC NMR. The results showed that the methoxyl group, hydroxyl group, interunit linkages, and thermal properties of the fractions varied with the molecular weight. The homogeneity of lignin was improved through solvent fractionation.