Mild Organosolv Delignification of Residual Aspen Bark after Extractives Isolation as a Step in Biorefinery Processing Schemes

European aspen (Populus tremula (L.) (Salicaceae)) bark is a promising raw material in multi-step biorefinery schemes due to its wide availability and higher content of secondary metabolites in comparison to stem wood biomass. The main objective of this study was to investigate the major cell wall component-enriched fractions that were obtained from aspen bark residue after extractives isolation, primarily focusing on integration of separated lignin fractions and cellulose-enriched bark residue into complex valorization pathways. The “lignin first” biorefinery approach was applied using mild organosolv delignification. The varying solvent systems and process conditions for optimal delignification of residual aspen bark biomass were studied using a response surface methodology approach. The conditions for maximum process desirability at which the highest amount of lignin-enriched fraction was separated were as follows: 20-h treatment time at 117 °C, butanol/water 4:1 (v/v) solvent system with solid to liquid ratio of 1 to 10. At optimal separation conditions, lignin-enriched fraction exhibited a higher content of β–O–4 linkages vs. C–C linkages content in its structure as well as a high amount of hydroxyl groups, being attractive for its further valorization. At the same time, the content of glucose in products of cellulose-enriched residue hydrolysis was 52.1%, increased from 10.3% in untreated aspen bark. This indicates that this fraction is a promising raw material for obtaining cellulose and fermentable glucose. These results show that mild organosolv delignification of extracted tree bark can be proposed as a novel biorefinery approach for isolation of renewable value-added products with various application potentials

Antioxidant Activity of Different Extracts from Black Alder (<i>Alnus glutinosa</i>) Bark with Greener Extraction Alternative

Phenolic compounds isolated from plant biomass consist of bioactive components showing a wide range of benefits for humans, including antioxidant, antimicrobial or anti-inflammatory effects. This paper presents the potential value of black alder (Alnus glutinosa (L.) Gaertn. (Betulaceae)) bark for the production of biologically active substances, despite its current use as a low value fuel source. Most of the extraction methods employ neat organic solvents to obtain extracts with a high antioxidant potential from biomass. The aim of this work is to show the advantages and disadvantages of the extraction process by taking into account the principles of ‘green chemistry’ and replacing the organic solvents with ‘green’ solvent water. Using the advantages of accelerated solvent extraction (ASE), it has been shown that the use of deionized water has the prospect of replacing organic solvents. In the case of the one-step water extraction, the total polyphenol content (TPC) varies from 0.55 to 0.62 Gallic acid equivalent (GAE) g/g in the extracts, depending on the temperature, whereas with the result of the sequential extraction with the organic solvents, the TPC content of the 40% (v:v) ethanol extracts ranges from 0.39 to 0.61 GAE g/g, depending on the temperature. The influence of the total polyphenol content and the total proanthocyanidin content on the antioxidant activity is shown. The antioxidant activity (IC50, mg/L) of the extracts obtained with the organic solvents in the (2,2-diphenyl-1-picrylhydrazyl) DPPH• test varies from 4.05 to 9.58, depending on the temperature in the range of 70–150 °C, respectively, while the results obtained with the deionized water showed promising results in the range of 6.33–7.36 in the temperature range of 70–150 °C, respectively. The extraction with the deionized water showed that approximately 90% of the substances in the extracts obtained with the organic solvents by sequential extraction are possible to obtain as deionized water extracts

Development of the approaches for complex utilization of brown algae (Fucus vesiculosus) biomass for the obtaining of value-added products

The seaweed collected after stranding on beaches of Latvia is underexploited natural resource, which has a potential as raw material for biologically active compound extraction for cosmetic and pharmacy and fertilizer in sustainable agriculture. The aim of the present study was development of the approach for the processing of brown alga Fucus vesiculosus biomass, collected from the Gulf of Riga. The thorough characterization of the chemical composition of Fucus vesiculosus has shown that it is a potential source for obtaining of nitrogen-containing fertilizers, and biologically active compounds. One of the proposed approaches for the processing of the Fucus vesiculosus biomass under study includes algae extraction with organic solvents and CaCl2 solution and obtaining soil organic amendment on the basis of the extract-free residue. The ethyl acetate extract was rich in phenolic compounds (430 ± 30 GAE mg/g) with high antioxidant activity in DPPH• and ABTS•+ tests. The ethanol extract contained significant amounts of phlorotannins that was confirmed by the data of LC-MS/MS analysis. The CaCl2 extract was used for the obtaining of sulphated polysaccharide fucoidane (yield ≈7% on the basis of oven dry matter, o.d.m.), which has numerous biological activities. The extract-free residue didn’t show phytotoxicity. The extract free algal biomass exhibited positive effect in root elongation tests with oat (Avena sativa). As alternative approach for processing of the algal biomass, the mechano-chemical treatment of algal biomass with lignin was proposed. EPR analyses confirmed interaction between algal biomass and lignin

Spent Coffee Grounds Valorization in Biorefinery Context to Obtain Valuable Products Using Different Extraction Approaches and Solvents

The valuable products that can be isolated from spent coffee ground (SCG) biomass consist of a high number of bioactive components, which are suitable for further application as raw materials in various production chains. This paper presents the potential value of the SCG obtained from large and local coffee beverage producers, for the production of valuable, biologically active products. Despite its high potential, SCG has not been utilized to its full potential value, but is instead discarded as waste in landfills. During its decomposition, SCG emits a large amount of CO2 and methane each year. The main novelty of our work is the implementation of sequential extraction with solvents of increased polarity that allows for the maximal removal of the available extractives. In addition, we have compared different extraction techniques, such as conventional and Soxhlet extraction, with more effective accelerated solvent extraction (ASE), which has seen relatively little use in terms of SCG extraction. By comparing these extraction methods and highlighting the key differences between them in terms of extraction yield and obtained extract composition, this work offers key insights for further SCG utilization. By using sequential and one-step accelerated solvent extraction, it is possible to obtain a significant number of extractives from SCG, with a yield above 20% of the starting biomass. The highest yield is for coffee oil, which is obtained with n-hexane ranging between 12% and 14% using accelerated solvent extraction (ASE) according to the scheme: n-hexane→ethyl acetate→60% ethanol. Using single-stage extraction, increasing the ethanol concentration also increases the total phenolic content (TPC) and it ranges between 18.7–23.9 Gallic acid equivalent (GAE) mg/g. The iodine values in the range of 164–174 using ASE and Soxhlet extraction shows that the hexane extracts contain a significant amount of unsaturated fatty acids; coffee oils with a low acid number, in the range of 4.74–6.93, contain few free fatty acids. The characterization of separated coffee oil has shown that it mainly consists of linoleic acid, oleic acid, palmitic acid, stearic acid and a small number of phenolic-type compounds

Solvent fractionation of softwood and hardwood kraft lignins for more efficient uses: compositional, structural, thermal, antioxidant and sorption properties

This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating values, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The aim was to develop a simple approach for the obtaining of lignin fractions with a tailored properties for the certain material applications.  Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations efficiently separated both spruce and eucalyptus kraft lignins into fractions with low polydispersities. The ethanol fraction of spruce and the ethyl acetate fraction of eucalyptus afforded the highest yields. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material was characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes in each experimental curve, and the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye. The clear correlation between certain structural features in the lignin fractions and the properties of the lignin provides useful information for selecting the appropriate solvent combinations for specific applications of lignin raw materials, including as antioxidants, biofuels or sorbents in water treatment processes.QC 20180821</p

Extraction possibilities of lipid fraction and authentication assessment of chaga (Inonotus obliquus)

Chaga (Inonotus obliquus) (Fr.) Pilát is a black perennial fungus that grows on adult birch trunk and traditionally been used as a health prevention remedy in different countries. The lipophilic compounds of chaga were isolated applying conventional (Soxhlet), non-conventional (ultra-sound assisted, accelerated solvent) and environmentally friendly (supercritical fluid) extraction methods utilizing both polar and non-polar solvents. For authentication of chaga samples, isotope ratio mass spectrometry (IRMS) and multi-elemental analysis was performed in this study. The yield and profile of lipids, sterols, and triterpenoids of various origins were discussed and potential application in terms of antimicrobial activity against pathogenic and opportunistic pathogenic microorganisms demonstrated. The results showed that CO2 extraction delivered comparable to conventional extraction techniques amount of target compounds with a safer profile and therefore could represent the future for sustainable industrial-scale production of biologically active ingredients with antimicrobial activity. Authentication of chaga allowed to establish the quality parameters and properties of resources that will be useful for industries

Mild Organosolv Delignification of Residual Aspen Bark after Extractives Isolation as a Step in Biorefinery Processing Schemes

European aspen (Populus tremula (L.) (Salicaceae)) bark is a promising raw material in multi-step biorefinery schemes due to its wide availability and higher content of secondary metabolites in comparison to stem wood biomass. The main objective of this study was to investigate the major cell wall component-enriched fractions that were obtained from aspen bark residue after extractives isolation, primarily focusing on integration of separated lignin fractions and cellulose-enriched bark residue into complex valorization pathways. The “lignin first” biorefinery approach was applied using mild organosolv delignification. The varying solvent systems and process conditions for optimal delignification of residual aspen bark biomass were studied using a response surface methodology approach. The conditions for maximum process desirability at which the highest amount of lignin-enriched fraction was separated were as follows: 20-h treatment time at 117◦C, butanol/water 4:1 (v/v) solvent system with solid to liquid ratio of 1 to 10. At optimal separation conditions, lignin-enriched fraction exhibited a higher content of β–O–4 linkages vs. C–C linkages content in its structure as well as a high amount of hydroxyl groups, being attractive for its further valorization. At the same time, the content of glucose in products of cellulose-enriched residue hydrolysis was 52.1%, increased from 10.3% in untreated aspen bark. This indicates that this fraction is a promising raw material for obtaining cellulose and fermentable glucose. These results show that mild organosolv delignification of extracted tree bark can be proposed as a novel biorefinery approach for isolation of renewable value-added products with various application potentials

Solvent fractionation of softwood and hardwood kraft lignins for more efficient uses: compositional, structural, thermal, antioxidant and sorption properties

This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating values, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The aim was to develop a simple approach for the obtaining of lignin fractions with a tailored properties for the certain material applications.  Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations efficiently separated both spruce and eucalyptus kraft lignins into fractions with low polydispersities. The ethanol fraction of spruce and the ethyl acetate fraction of eucalyptus afforded the highest yields. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material was characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes in each experimental curve, and the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye. The clear correlation between certain structural features in the lignin fractions and the properties of the lignin provides useful information for selecting the appropriate solvent combinations for specific applications of lignin raw materials, including as antioxidants, biofuels or sorbents in water treatment processes.QC 20180821</p

Characterization of Softwood and Hardwood LignoBoost Kraft Lignins with Emphasis on their Antioxidant Activity

Fractionation of softwood and hardwood LignoBoost kraft lignins, using sequential extraction with organic solvents of increasing hydrogen-bonding ability (dichloromethane, n-propanol, and methanol), was carried out. Using SEC, analytical pyrolysis, FTIR and UV/VIS spectroscopy, and chemical analytical methods, four fractions were obtained and characterized in terms of their yield, composition, functionality, lignin structural features, and antioxidant properties. In tests with free radicals (ABTS●+, DPPH●, O2●-) and the ORAC (oxygen radical absorbance capacity) assay, the high radical scavenging capacity of the lignin’s soluble fractions was demonstrated. The antioxidant activity of the fractions was tested by their influence on thermo-oxidative destruction of model polyurethane elastomers. The TGA data clearly revealed the antioxidant effect of the three fractions, with the most prominent activity for the propanol-soluble fraction. The dichloromethane fraction has potential as an antioxidant for non-polar products. Novel correlations between lignin’s structural features and its radical scavenging activity were found that can be used for tuning lignin’s antioxidant properties