Loading...
5 results
Search Results
Now showing 1 - 5 of 5
- Distillery residues from Cistus ladanifer (Rockrose) as feedstock for the production of added-value phenolic compounds and hemicellulosic oligosaccharidesPublication . Alves Ferreira Caturra, Júnia Aparecida; Duarte, Luís C.; Lourenço, Ana; Roseiro, Luisa B.; C. Fernandes, M.; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: Cistus ladanifer residues obtained after essential oil distillation were extracted with ethanol and water (CLRext) and subsequently hydrothermally treated (autohydrolysis) in order to selectively hydrolyze hemicelluloses. The extraction removed a significant amount of potentially valuable compounds (40% w/w, dry basis), foremost, phenolic compounds (0.363 and 0.250 g gallic acid equivalent/g extract, respectively, for water and ethanol). Autohydrolysis was studied under diverse severity factors (log R-o), in the temperature range of 150 to 230 degrees C. The hydrolyzates mainly contain oligosaccharides, reaching the highest concentration (23.5g/L) for log R-o of 3.07 (190 degrees C), corresponding to a yield of 15g oligosaccharides/100g dry feedstock. The processed solids are enriched in glucan and lignin. The maximum glucan content (35%) was attained at log R-o of 3.51 (205 degrees C). Py-GC/MS confirmed the reduction of pentose-derived carbohydrates in the solid after hydrothermal treatment and an increase of syringil units in the lignin compared to the untreated biomass. These results show the potential use of this C. ladanifer residue for the production of phenolic extracts, and hemicellulosic oligosaccharides, together with the production of a cellulose- and lignin-rich solid stream.
- Cistus ladanifer as a source of chemicals : structural and chemical characterizationPublication . Alves Ferreira Caturra, Júnia Aparecida; Miranda, Isabel; Duarte, Luís C.; Roseiro, Luisa B.; Lourenço, Ana; Quilhó, Teresa; Cardoso, Sofia; Fernandes, M. C.; Carvalheiro, Florbela; Pereira, HelenaABSTRACT: Different biomass fractions of Cistus ladanifer and solid residues from essential oil distilleries were structurally and chemically evaluated. The C. ladanifer biomass fractions showed chemical differences mainly related to extractives (e.g., 10.8% and 53.7% in stems and leaves) and lignin (e.g., 21.2% and 15.4% in stems and leaves). The distillery residues were characterized by 41.5% extractives and 19.3% lignin, and polysaccharide glucose 51.7% and xylose 24.9% of total monosaccharides. The polar extracts had a high content of phenolics and revealed high antioxidant activity (IC50 3.2 μg/mL and 4.7 μg/mL in stems and cysts extracts). The lignin structure showed a predominance of S units in the stem (H:G:S of 1:25:50) and a balanced proportion of H, G, and S units in leaves (H:G:S of 1:1.4:1). The characteristics of C. ladanifer biomass allow several routes of valorization. The high extractive contents point out to the potential use as a source of phytochemicals by applying extraction procedures, while the remaining lignocellulosic material after extraction may be directed towards lignin and carbohydrates applications. The use of C. ladanifer biomass for an extractives-lignocellulosic-based biorefinery therefore represents a potential valorization that may contribute to additional revenue for the present essential oil distilleries.
- The behavior of thermally modified wood after exposure in maritime/industrial and urban environmentsPublication . Godinho, Delfina; Ferreira, Cristina; Lourenço, Ana; Araújo, Solange; Quilhó, Teresa; Cunha Diamantino, Teresa; Gominho, JorgeABSTRACT: Natural and thermally modified Pine, Ash, and Acacia woods were exposed in two different environments: urban and maritime/industrial. The weathering effects were evaluated during 24 months regarding color, chemical, and structural changes. In all wood species, thermal modification induced color, chemical, and structural changes. All woods became darker (Pine Delta L*: -32.01; Ash Delta L*: -36.83; Acacia Delta L*: -27.50), total extractives content increased (Pine: 19 %; Ash: 32 % and Acacia: 18 %), and the samples presented deformation and damaged cells. Total lignin was not significantly changed, although there were detected changes in lignin, namely the reduction of G -units in Pine (approximate to 2 %) and reduction of S/G ratio in Acacia (approximate to 0.04 %). Ash remained almost the same. After weathering, modified woods suffered fewer color changes, indicating that the thermal modification could improve the resistance to color change. Acacia wood, when exposed to maritime/industrial conditions, revealed a higher color change (Delta E: 35.7 at 24 months) when compared with urban conditions (Delta E: 23.5 at 24 months). Delignification, possibly caused by photodegradation, occurred in all wood samples, and the loss of extractive happened, perhaps caused by rain. Modified woods were slightly less resistant to weathering in maritime/ industrial environments. Some structural damage, namely cracked cells, the appearance of molds, blue staining, and particle deposition, was observed. The thermal modification enables color stabilization but does not seem to improve the weathering resistance in all studied wood species. Exposure to the different environments did not lead to significant differences in the morphology and chemical composition of the three natural and modified wood species.
- Delignification of Cistus ladanifer Biomass by Organosolv and Alkali ProcessesPublication . Alves Ferreira Caturra, Júnia Aparecida; Lourenço, Ana; Morgado, Francisca; Duarte, Luís C.; Roseiro, Luisa B.; Fernandes, M. C.; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: Residues of Cistus ladanifer obtained after commercial steam distillation for essential oil production were evaluated to produce cellulose enriched solids and added-value lignin-derived compounds. The delignification of extracted (CLRext) and extracted and hydrothermally pretreated biomass (CLRtreat) was studied using two organosolv processes, ethanol/water mixtures (EO), and alkali-catalyzed glycerol (AGO), and by an alkali (sodium hydroxide) process (ASP) under different reaction conditions. The phenolic composition of soluble lignin was determined by capillary zone electrophoresis and by Py-GC/MS, which was also used to establish the monomeric composition of both the delignified solids and isolated lignin. The enzymatic saccharification of the delignified solids was also evaluated. The ASP (4% NaOH, 2 h) lead to both the highest delignification and enzymatic saccharification (87% and 79%, respectively). A delignification of 76% and enzymatic hydrolysis yields of 72% were obtained for AGO (4% NaOH) while EO processes led to lower delignification (maximum lignin removal 29%). The residual lignin in the delignified solids were enriched in G- and H-units, with S-units being preferentially removed. The main phenolics present in the ASP and AGO liquors were vanillic acid and epicatechin, while gallic acid was the main phenolic in the EO liquors. The results showed that C. ladanifer residues can be a biomass source for the production of lignin-derivatives and glucan-rich solids to be further used in bioconversion processes.
- Chemical composition and structural features of cellolignin from steam explosion followed by enzymatic hydrolysis of Eucalyptus globulus barkPublication . Magina, Sandra; Marques, Susana; Gírio, Francisco; Lourenço, Ana; Barros-Timmons, Ana; Evtuguin, Dmitry V.ABSTRACT: Bark is one of the main wastes of the chemical and mechanical processing of Eucalyptus globulus wood. The proposed biochemical processing of bark via saccharification pathway involves steam explosion (SE) pretreatment (severity factor log R0 of 4.22) followed by enzymatic hydrolysis using an enzymatic cocktail composed of cellulolytic and xylanolytic enzymes. Almost 70% cellulose saccharification was achieved. The remaining cellolignin residue (CLEZ) was analysed for its chemical composition and structural features by conventional wet chemistry methods and a series of spectroscopic tools (FTIR-ATR, solid-state CP/MAS C-13 NMR spectroscopy and wide-angle X-ray scattering (WAXS)). The main CLEZ component (about 51%) is acid-insoluble lignin, the chemical composition of which in terms of the ratio of syringyl (S), guaiacyl (G) and p-hydroxyphenyl (H) units (70:28:2) is very close to that in the initial bark. This lignin is highly condensed and structurally associated with condensed tannins, which makes CLEZ recalcitrant to delignification by common methods. About one third of cellulose in eucalyptus bark after SE was inaccessible to enzymatic hydrolysis and remained in the CLEZ. This cellulose, structurally similar to microcrystalline cellulose, is imbedded into the lignin-tannins condensed matrix and extremely difficult to purify. In contrast to cellulose, bark hemicelluloses were effectively removed in enzymatic hydrolysis, with only small amounts (<2%) remaining in CLEZ. Among other CLEZ ingredients, proteins and inorganic/organic salts were the most abundant. The latter includes noticeable amounts of calcium oxalate phytoliths (up to 9%), Fe and Si salts. The eventual application areas of CLEZ are discussed.