Valorisation of waste fractions from autohydrolysis of selected lignocellulosic materials (original) (raw)
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Trends in Food Science & Technology, 2004
Mild acid treatments of lignocellulosic materials result in hemicellulose conversion into sugar and sugar oligomers as well as in solubilization of phenolic compounds with potential food applications. The effect of the operational conditions (measured by the severity factor) on the yield of soluble phenolics and the utilization of these compounds (with antioxidant and antimicrobial activities) as food additives are reviewed. Additional information on other biological effects of phenolics that could be of interest for the formulation of functional foods is provided.
Journal of Food Engineering, 2008
Non-isothermal treatments of barley husks in aqueous media were performed under a variety of operational conditions, to cause the hydrolytic degradation of hemicelluloses. The amount and composition of solid and liquid phases were determined. Liquors from treatments were extracted with ethyl acetate in order to remove non-saccharide components (mainly derived from the extractive acid-soluble lignin fractions), and the extracted fractions were quantified and assayed for antioxidant activity using the DPPH radical scavenging test. Posthydrolysis of autohydrolysis liquors led to xylose-containing solutions suitable as fermentation media. The dependence of the major process parameters (concentrations of monosaccharides and monosaccharide-degradation products obtained after autohydrolysis-posthydrolysis, yield of ethyl acetate soluble compounds and antioxidant activity of isolates) on the severity of treatments was assessed. The ethyl acetate soluble fraction obtained under the best processing conditions showed an antioxidant activity in the range reported for synthetic antioxidants.
Lignocellulosic Biomass as Source for Lignin-Based Environmentally Benign Antioxidants
Molecules
Antioxidant activity is an essential aspect of oxygen-sensitive merchandise and goods, such as food and corresponding packaging, cosmetics, and biomedicine. Technical lignin has not yet been applied as a natural antioxidant, mainly due to the complex heterogeneous structure and polydispersity of lignin. This report presents antioxidant capacity studies completed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The influence of purification on lignin structure and activity was investigated. The purification procedure showed that double-fold selective extraction is the most efficient (confirmed by ultraviolet-visible (UV/Vis), Fourier transform infrared (FTIR), heteronuclear single quantum coherence (HSQC) and 31P nuclear magnetic resonance spectroscopy, size exclusion chromatography, and X-ray diffraction), resulting in fractions of very narrow polydispersity (3.2–1.6), up to four distinct absorption bands in UV/Vis spectroscopy. Due to differential scanning calorimetry measurem...
Antioxidant and Antimicrobial Effects of Extracts from Hydrolysates of Lignocellulosic Materials
Journal of Agricultural and Food Chemistry, 2001
The antioxidant and antimicrobial activities of ethyl acetate extracts obtained from acid hydrolysates of several lignocellulosic materials (Eucalyptus globulus wood, barley bran, corn cobs, and corn leaves) were evaluated. The minimum inhibitory and bactericide concentrations (MIC and MBC, respectively) were determined against a selection of bacteria and yeasts. Extracts from Eucalyptus wood hydrolysates were the most active for inhibiting bacteria and yeast growth, with MIC in the range of 10 2-5 × 10 3 µg/mL and MBC in the range of 10 3-10 5 µg/mL. Bacteriogenic and bacteriostatic activities of extracts from Eucalyptus wood and barley bran acid hydrolysates were slightly higher than those of corn cobs and leaves. Both the radical scavenging capacity and the inhibition of the-carotene bleaching caused by extracts were determined and compared with those of synthetic antioxidants. The antioxidant activity of extracts increased with their concentrations in the media, the stronger properties corresponding to those obtained from Eucalyptus wood hydrolysates.
Phenolics production from alkaline hydrolysis of autohydrolysis liquors
CyTA - Journal of Food, 2015
The objective of this work was to study the release, identification and characterization of phenolic compounds by saponification of nonisothermal autohydrolysis liquors of corn (Zea mays) cobs and Eucalyptus globulus. Corn cobs and E. globulus are lignocellulosic materials with high contents in cellulose and hemicelluloses. Efficient use of these materials can be achieved using autohydrolysis as the first stage of a biorefinery, resulting in a solid phase rich in cellulose and lignin, and a liquid phase containing essentially hemicelluloses-derived compounds and phenolic compounds from the partial solubilization of lignin. This work studied the combination of alkaline hydrolysis and extraction with organic solvents to maximize the amounts of released phenolic compounds since these compounds are interesting for their properties and food applications.
Scientific Works - University of Agronomical Sciences and Veterinary Medicine, Bucharest. Series C, Veterinary Medicine, 2012
The paper presents the results of fractioning the biomass towards its bioconversion to ethanol for both – the carbohydrates resulting from hemicelluloses and from the ones of the lignocellulosic complex. Therefore not only methods of chemical hydrolysis were applied, but enzymatic ones too, using products developed in our own laboratories. Also, the possibility of turning into account the phenolic compounds – with high antioxidant potential – was closely looked into, as the phenols are the result of the enzymatic cleavage of the lignocellulosic edifice, rigidly structured. This treatment, unlike the acid hydrolysis, does not cause degradations in the aromatic structures, when submitted to high temperatures. The distillation process, as well as the correction one for the ethanolic solutions that came both from the pretreatment phase and from the celluloso – lythical saccharification phase were performed in the same fashion, using the identical methodology. The results were, therefore...
Food Chemistry, 1999
Eucalyptus wood hydrolysates were extracted with organic solvents (ethyl acetate and diethyl ether) to remove part of the phenolics derived from lignin. In order to obtain increased phenolic removal, the eects of the major experimental variables aecting extraction (type of solvent, hydrolysate to solvent volume ratio, temperature, pH and coupling of extraction stages) were explored. Under the best operational conditions, up to 84% of the initial lignin-derived compounds were extracted. The phenolic compounds extracted by solvents showed antioxidant activity. Under the best conditions, the antioxidant activity coecient was 64% of the value found with a synthetic antioxidant (BHT). Extracted hydrolysates led to xylose solutions, allowing an enhanced fermentative production of xylitol with the yeast Debaryomyces hansenii.
Characterization of the radical scavenging activity of lignins––natural antioxidants
Bioresource Technology, 2004
The present work is devoted to studies of the radical scavenging properties of lignins, which are recognized as efficient antioxidants of natural origin. Radical scavenging efficiency of a series of lignins isolated from deciduous and coniferous wood species and 10 lignin related monomeric compounds were examined against 1,1-diphenyl-2-picrylhydrazyl (DPPH Å ) radical in homogeneous conditions using ESR and spectrophotometry methods. Some structure-activity relationships are proposed, pointing out the importance of the non-etherified OH phenolic groups, ortho-methoxy groups, hydroxyl groups and the double bond between the outermost carbon atoms in the side chain for increasing scavenger activity. Analysis of rate constants for the lignins-DPPH Å interaction revealed the contribution of polymer molecular weight and p-polyconjugation systems. The p-conjugation systems of lignins operate as catalysts/activators of the interaction with DPPH Å . Heterogeneity in terms of component composition (carbohydrate admixtures) and polydispersity is the factor which can decrease drastically the antioxidant efficiency of isolated lignins. The connection of the antibacterial effect of kraft lignin with radical scavenging activity of its soluble fraction was assumed.
Journal of the Chilean Chemical Society, 2015
Eucalyptus globulus wood chips were subjected to autohydrolysis pretreatment at 175ºC at three different residence times. Part of the recovered solids were submitted to alkaline extraction with NaOH solution to remove leachable lignin. The chemical composition of the fibrous material was analyzed by HPLC, Py-GCMS and 2D-NMR HSQC, while morphological changes were evaluated by SEM and LSCM. The pretreated materials were hydrolyzed with cellulases at a substrate loading of 10% (w/v) for up to 72 h. Glucose yields (based on dry wood) obtained in the enzymatic hydrolysis ranged between 38% and 65%, depending on reaction time in the autohydrolysis pretreatment. After the alkaline extraction, no significant change was observed in the yields in the enzymatic hydrolysis at 72 h, but at the lower severities, the initial rates of saccharification increased. The main effect of the hydrothermal pretreatment was removal of hemicelluloses, resulting in enriched cellulose pulps. SEM and LSCM images of the hydrothermal pretreated samples showed a disruption of the fiber surface, mainly in those samples obtained at the higher severity. Py-GC/MS and HSQC analysis showed that no major changes in the lignin structure occurred in the samples obtained by autohydrolysis and further alkaline extraction. By autohydrolysis at the higher severity (So=4.02), the lateral chains in lignin were cleaved and the formation of lignin droplets was observed. Hemicelluloses removal and lignin redeposition as droplets in certain regions of the fiber surface was associated with the higher accessibility of cellulose and the yield increase of the enzymatic hydrolysis.