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- Hydrothermal processing of hardwoods and agro-industrial residues :evaluation of xylo-oligosaccharides productionPublication . Carvalheiro, Florbela; Fernandes, Talita Silva; Duarte, Luís C.; Lopes, Sónia; Moura, Patrícia; Pereira, Helena; Gírio, FranciscoAutohydrolysis was used as a pre-treatment method for the selective hydrolysis of hemicelluloses of four lignocellulosic materials: eucalypt wood chips (EWC), corn cobs (CC), wheat straw (WS) and brewery’s spent grain (BSG), and the process was optimized towards the production of xylo-oligosaccharides (XOS). The effects of temperature, both at isothermal (150-190ºC), and non-isothermal (up to 240ºC) conditions, and liquid-to-solid ratio (LSR), 8 or 10 g/g, on the composition of both the liquid and solid phases were studied. The operational conditions leading to the maximal recovery of XOS for each raw material were established and discussed based on the severity factor (log R0). The higher yields obtained were in the range of 43–65% of the feedstock (arabino)xylan, with the highest value attained for CC for log R0 =3.75. Under the optimised conditions for XOS production, glucan was only slightly solubilised, enabling an enrichment of the solid phase (up to 67% of glucan for EWC). Delignification was also not extensive reaching utmost 18%, in the case of CC. cosmetic industries.
- Thermal modification on eucalyptus wood : an essayPublication . Knapic, Sofia; Santos, José António dos; Pereira, Helena
- 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.
- Hydrothermal processing of corn residues:process optimisation and products characterisationPublication . Moniz, Patricia; Gírio, Francisco; Carvalheiro, Florbela; Pereira, HelenaHydrothermal processing was used as pre-treatment method for the selective solubilisation of hemicellulose from corn residues (leaves and stalks). The raw material was treated at a liquidto- solid ratio of 10 g/g, under non-isothermal conditions (150-240ºC) and the effect of treatment on the composition of both liquid and solid phases was evaluated. The yields of solid residue and soluble products, e.g., oligosaccharides, monosaccharides, acetic acid and degradation compounds, such as furfural, hydroxymethylfurfural are presented and interpreted using the severity factor (log R0). The operational conditions leading to the maximum recovery of XOS (53% of initial (arabino)xylan) and for highest glucan content of the solid residue (64%) were established for log R0 of 3.75 and 4.21, respectively. Under the severest condition 95% of xylan was selectively solubilised and 90% of initial glucan was recovered on the solid residue, making it very attractive for further processing in a biorefinery framework.
- Fractionation of hemicelluloses and lignin from rice straw by combining autohydrolysis and optimised mild organosolv delignificationPublication . Moniz, Patricia; Lino, João; Duarte, Luís C.; Roseiro, Luisa B.; Boeriu, Carmen G.; Pereira, Helena; Carvalheiro, FlorbelaAn integrated strategy was followed to valorise rice straw, one of the most relevant biomass feedstocks available worldwide, to selectively recover solubilised hemicelluloses and lignin. The pathway encompassed the use of autohydrolysis to hydrolyse the hemicelluloses and an ethanol-based organosolv process to solubilise lignin. Several autohydrolysis conditions were assayed with the best results obtained at 210 ºC (log R0 4.15), which enabled high removal of hemicelluloses, yielding an oligosaccharide-rich hydrolysate and a treated biomass with low content of hemicelluloses and enriched in cellulose and lignin. The effects of ethanol concentration (5 to 75%), and reaction time (0 to 24 h) on lignin removal under mild temperature (30 ºC) were studied. In optimal conditions (60.5% ethanol, 24h) the delignification yield reached 42%, where as glucan solubilisation was below 17%. Lignin solubilisation yield was not influenced by the organosolv treatment duration while ethanol concentration favored the delignification up to 60.5% ethanol. The organosolv liquors contained economic interesting ligninderived compounds such as vanillin, ferulic, and coumaric acids. The chemical composition and enzymatic digestibility of the treated biomass from autohydrolysis and organosolv delignification were compared, with the latter presenting an almost 10% higher enzymatic digestibility than the former.
- D-lactic acid production from hydrothermally pretreated, alkali delignified and enzymatically saccharified rockrose with the metabolic engineered Escherichia coli strain JU15Publication . Fernandes, M. C.; Alves Ferreira Caturra, Júnia Aparecida; Duarte, Luís C.; Pereira, Helena; Carvalheiro, Florbela; Martinez, AlfredoABSTRACT: Rockrose lignocellulosic residues (RR) were selectively fractionated for hemicellulose separation using autohydrolysis, followed by an alkaline treatment to solubilize the lignin. The cellulose-enriched solids were used to study the effect of solid loading (SL: 2-10%) and enzyme dosage (ED: 6.34-23.66 FPU/g dry biomass) on saccharification using a Doehlert experimental design, followed by fermentation with the metabolic engineered Escherichia coli strain JU15 to produce D-lactic acid (DLA). Pretreatment increased glucan content and enzymatic digestibility up to 84%. A significant positive effect of SL and ED was found for glucose production, but SL negatively impacted glucose yield. DLA concentrations and productivity varied from 8.85 to 32.98 g/L and 1.11 to 2.17 g/(Lh), respectively. Overall process efficiency strongly depended on saccharification yield and varied from 33 to 71%. These results indicate that sequential autohydrolysis, delignification, and fermentation of RR may be a potential relevant strategy for D-lactic production in the biorefinery framework.
- Hydrothermal production and gel filtration purification of xylo-oligosaccharides from rice strawPublication . Moniz, Patricia; Pereira, Helena; Duarte, Luís C.; Carvalheiro, FlorbelaHydrothermal treatment (autohydrolysis) is an advantageous alternative to fractionate biomass that was not yet explored for rice straw. In this work, the process was optimised and proved to be highly selective towards hemicellulose. Hydrolysates containing a mixture of oligomeric compounds (mainly xylo-oligosaccharides, XOS), could be obtained under relatively mild operation conditions (210 degrees C, logR(0) = 3.59), yielding a maximum of 40.1 g/100 g of initial xylan. The produced XOS were separated by molecular mass using gel filtration chromatography (GFC). Different fractions of purified XOS were obtained ranging from small polysaccharides and high DP oligosaccharides (DP >= 23), to medium and low DP oligosaccharides (DP >= 3), and separated fractions of by-products (acetic acid, furan derivatives and phenols) as well as di-, and monosaccharides. GFC was an efficient purification method enabling the recovery of interesting categories of XOS that can have potential applications to the pharma, food and feed industries.
- 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.
- Production of Oligosaccharides from Pine Nut Shells by AutohydrolysisPublication . Torrado, Ivone; Dionísio, Ana; Fernandes, M. C.; Roseiro, Luisa B.; Carvalheiro, Florbela; Pereira, Helena; Duarte, Luís C.ABSTRACT: Pinus pinea nuts are commercial relevant Mediterranean edible forest nuts, with an increasing production and market value, whose industrial processing yields a lignocellulosic by-product, the pine nut shells, currently only used for combustion. Little research has been done on pine nut shells that could support a value-added application for this residue. This work studies for the first time the production of oligosaccharides by autohydrosis, and aims at an integrated upgrade within the biorefinery framework. Autohydrolysis was explored in the temperature range between 150 and 230 degrees C (corresponding to severity factors 2.13-4.63). Oligosaccharides, mainly xylo-oligosaccharides (95% of the total), were the key soluble products, reaching 28.7 g/100 g of xylan of the feedstock at the optimal conditions (log R-0 4.01). Other products were monosaccharides and phenolic compounds that reached 7.8 and 4.7 g/L, respectively, under the most severe conditions. The stability of the oligosaccharides at different temperatures (room, 37 degrees C and 100 degrees C) and pH (between 1 and 11) grant them significant market potential in the food and pharma sectors. The pre-treated pine nut shells by autohydrolysis presented an improved, although low, enzymatic digestibility (14%), and an improved high-heating value, therefore advising their further valorization by thermochemical pathways.
- Cistus ladanifer as a Potential Feedstock for Biorefineries: A ReviewPublication . Alves Ferreira Caturra, Júnia Aparecida; Duarte, Luís C.; Fernandes, M. C.; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: Cistus ladanifer (rockrose) is a widespread shrub species in the Mediterranean region well known due to its production of labdanum gum, especially in the hot season. Its leaves and branches can be subjected to different extraction and distillation processes to produce various types of extracts. The natural extracts of C. ladanifer have several applications, especially in the perfumery and cosmetics sector. C. ladanifer extracts, in addition to presenting interesting odoriferous properties, are also known for their bioactive properties, such as antioxidant and antimicrobial. Use of this species in animal feed or phytostabilisation of mining areas has also been successfully applied. On the other hand, the lignin and polysaccharides that are the major fractions from Cistus residues can be relevant sources of high-value products in a biorefinery framework. Recently, it has been reported that the residues obtained from the essential oil industry can sustain production of significant amounts of other marketable products, namely phenolic compounds, oligomeric and monomeric sugars, lignin, and lactic acid. All these applications show the potential of C. ladanifer as a raw material to be fully valued in a biorefinery context, contributing to important revenues and generating an associated marketable biobased product portfolio.