Molecular Characteristics and Antioxidant Activity of Spruce (Picea abies) Hemicelluloses Isolated by Catalytic Oxidative Delignification

Abstract

Spruce (Piceaabies) wood hemicelluloses have been obtained by the noncatalytic and catalytic oxidative delignification in the acetic acid-water-hydrogen peroxide medium in a processing time of 3–4 h and temperatures of 90–100 °C. In the catalytic process, the H2SO4, MnSO4, TiO2, and (NH4)6Mo7O24 catalysts have been used. A polysaccharide yield of up to 11.7 wt% has been found. The hemicellulose composition and structure have been studied by a complex of physicochemical methods, including gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The galactose:mannose:glucose:arabinose:xylose monomeric units in a ratio of 5:3:2:1:1 have been identified in the hemicelluloses by gas chromatography. Using gel permeation chromatography, the weight average molar mass Mw of hemicelluloses has been found to attain 47,654 g/mol in noncatalytic delignification and up to 42,793 g/mol in catalytic delignification. Based on the same technique, a method for determining the α and k parameters of the Mark–Kuhn–Houwink equation for hemicelluloses has been developed; it has been established that these parameters change between 0.33–1.01 and 1.57–472.17, respectively, depending on the catalyst concentration and process temperature and time. Moreover, the FTIR spectra of the hemicellulose samples contain all the bands characteristic of heteropolysaccharides, specifically, 1069 cm−1 (C–O–C and C–O–H), 1738 cm−1 (ester C=O), 1375 cm−1 (–C–CH3), 1243 cm−1 (–C–O–), etc. It has been determined by the thermogravimetric analysis that the hemicelluloses isolated from spruce wood are resistant to heating to temperatures of up to ~100 °C and, upon further heating, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses has been examined using the compounds simulating the 2,2-diphenyl-2-picrylhydrazyl free radicals.

Preparation, Characterization and Anti-Complementary Activity of Three Novel Polysaccharides from Cordyceps militaris

“…Obviously, the CMP-1, CMP-2 and CMP-3 were composed of at least 10 kinds of different monosaccharides, which were more abundant than the previously reported polysaccharides from C. militaris . Compared with polysaccharides from other sources (including other fungi, algae and plants) [ 32 , 33 ], they were usually composed mainly of glucose and galactose in their monosaccharide composition. However, glucosamine in these three polysaccharides was rarely found in polysaccharides from plants.…”

The Structural Characteristics of an Acidic Water-Soluble Polysaccharide from Bupleurum chinense DC and Its In Vivo Anti-Tumor Activity on H22 Tumor-Bearing Mice

“…The effects of different extraction temperature (70 °C, 90 °C) and ethanol concentration (60%, 70%, 80%) on the molecular weight of Bupleurum chinense DC polysaccharide were compared. Six samples were prepared for analysis [ 29 ]. The average molecular weight of BCP was evaluated by HPGPC (Agilent Technologies, Palo Alto, CA, USA).…”

Composition and Structure of Aspen (Pópulus trémula) Hemicelluloses Obtained by Oxidative Delignification

“…Recently, there has been a steadily growing trend toward the replacement of fossil fuels by lignocellulosic biomass biofuels. Lignocellulosic biomass has been proven to be an ideal alternative resource, and due to its large amount, short regeneration cycle, biodegradability, and environmental friendliness, can significantly reduce the amount of fossil sources used [ 4 , 5 , 6 ].…”

“…The main components of lignocellulosic biomass are cellulose, hemicellulose, and lignin. Although cellulose is the most widely used polysaccharide [ 7 , 8 , 9 , 10 ], hemicellulose, being the second most common renewable natural polymer, remains understudied, but has attracted increasing attention [ 11 ] as a potential resource for application in various fields [ 4 , 12 , 13 ]. Depending on the type of raw material used, hemicelluloses can have different compositions: in deciduous plant species, partially acetylated xylans dominate, while coniferous species consist mainly of glucomannans [ 14 ].…”

“…In early studies [ 21 , 22 ], various biomass pretreatment methods were used, but few of them have proven their efficiency. A promising pretreatment method is oxidative delignification in an acetic acid-water-hydrogen peroxide medium characterized by a high ability of separating lignin from cellulose and hemicellulose without their degradation and use of high temperatures or strong acids [ 4 , 18 , 23 , 24 , 25 ]. In this delignification process, hydrogen peroxide and acetic acid react with the formation of peracetic acid, which converts the lignin aromatic rings into carboxylic acids by oxidative cleavage [ 4 , 25 ].…”