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To understand the structural changes of lignin after soda-AQ and kraft pretreatment, milled straw lignin, black liquor lignin and residual lignin extracted from wheat straw were characterized by FT-IR, UV, GPC and NMR. The results showed that the main lignin linkages were β-aryl ether substructures (β-O-4'), followed by phenylcoumaran (β-5') and resinol (β-β') substructures, while minor content of spirodienone (β-1'), dibenzodioxocin (5-5') and α,β-diaryl ether linkages were detected as well. After pretreatment, most lignin inter-units and lignin-carbohydrate complex (LCC) linkages were degraded and dissolved in black liquor, with minor amount left in residual pretreated biomass. In addition, through quantitative (13)C and 2D-HSQC NMR spectral analysis, lignin and LCC were found to be more degraded after kraft pretreatment than soda-AQ pretreatment. Furthermore, the subsequent enzymatic hydrolysis results showed that more cellulose in wheat straw was converted to glucose after kraft pretreatment, indicating that LCC linkages were important in the enzymatic hydrolysis process., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In most native lignins, at least 50% of the phenylpropane (C(9)) units are involved in β-O-4 linkages. It was recently observed that ethylguaiacol (EG) was efficient at trapping coniferyl alcohol generated from the cleavage of uncondensed β-O-4 dimeric structures during soda-anthraquinone (AQ) or SAQ delignification of sugar maple wood meal. Some of the coniferyl alcohol was transformed to vinylguaiacol and isoeugenol, and the α-carbon atom in all three monomers formed C-C bonds with the C-5 position of EG. In the present research, eucalyptus and sugar cane bagasse meals were also investigated, and the yields of uncondensed β-O-4 structures in the nonsyringyl fraction were quantitated. The estimates of the uncondensed fraction of the lignin in the three samples (assuming S units are 90-95% uncondensed) were in close agreement with results from traditional but more tedious methods such as permanganate oxidation or spectroscopic methods requiring a sample representative of native lignin.

The positive aspects of the non-sulfur soda/anthraquinone (SAQ) process are mostly tied to improved energy efficiency while lower pulp brightness after bleaching is its most significant drawback. A credible method that quantifies bleachability as well as an approach that solves the problem for SAQ pulps from hardwoods will be described. A straight line correlation (R2=0.904) was obtained between O2 kappa number and final light absorption coefficient (LAC) value after standardized OD0EpD1 bleaching of nine hardwood kraft pulps from three laboratories and one pulp mill. The bleachability of pulps from four different soda processes catalyzed by anthraquinone (AQ) and 2-methylanthraquinone (MAQ) was compared to that of conventional kraft pulps by comparing O2 kappa number decrease and final LAC values. It was observed that a mild hot water pre-hydrolysis improved the bleachability of SAQ pulps to a level equal to that of kraft.

A sulfated emodin glucoside, emodin 8-O-beta-D-glucopyranosyl-6-O-sulfate (1), was isolated from the roots of Rheum emodi in an investigation of the active constituents of this Nepalese medicinal plant, and its structure was determined by spectroscopic and chemical methods. Additionally, two rare auronols, carpusin (2) and maesopsin (3), besides other anthraquinones and phenolics, were isolated and identified. Compounds 2 and 3 showed significant antioxidant activity in the DPPH assay, while chrysophanol, physcion, and emodin and their 8-O-glucosides were found to be inactive.

This is a new technique to assay virtually any endoglycanase activity where enough polysaccharide material is available to allow for production of the amorphous, dyed beads used as substrates. It allows for a direct comparison of endoglycanase activities between laboratories since dyed beads from at least the most common polysaccharides such as cellulose, xylan, mannan, and chitin are now under development and will soon be commercially available; cellulose beads already are. It is a very sensitive technique and enzyme activities can be measured using a nonsophisticated spectrophotometer., (Copyright 2000 Academic Press.)