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- 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.
- 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.
- Evaluation of different fractionation methods for the simultaneous protein and carbohydrate extraction from microalgaePublication . Martins, Pedro L.; Duarte, Luís C.; Pereira, Helena; Reis, Alberto; Carvalheiro, FlorbelaABSTRACT: The production of high-value products from microalgae, one of the preferred emerging biorefineries' feedstocks, relies on the crucial step of biomass fractionation. In this work, the fractionation of Chlorella vulgaris and Scenedesmus obliquus biomass was tested for protein extraction using a wide range of physical, chemical, and enzymatic treatment combinations, including ultrasound, cell homogenizer, cellulase, and alcalase combinations in aqueous and alkali extraction conditions. The impact of these processes on biomass carbohydrates was also evaluated. Alkaline-assisted ultrasound treatments using alcalase presented the highest protein extraction yield, reaching 90 g/100 g protein on C. vulgaris, closely followed by the same treatment in aqueous conditions (85 g/100 g protein). The same aqueous treatment achieved the best performance on S. obliquus, reaching 82 g/100 g protein. All treatments on both microalgae partially solubilized the polysaccharide fraction with all alkaline treatments solubilizing over 50 g/100 g sugars for all conditions. Overall, all the treatments applied were effective methods for biomass fractionation, although they showed low selectivity regarding the individual extraction of protein or carbohydrates.
- Membrane separation and characterisation of lignin and its derived products obtained by a mild ethanol organosolv treatment of rice strawPublication . Moniz, Patricia; Serralheiro, Cláudia; Matos, Cristina T.; Boeriu, Carmen G.; Frissen, Augustinus E.; Duarte, Luís C.; Roseiro, Luisa B.; Pereira, Helena; Carvalheiro, FlorbelaABSTRACT: An organosolv process using ethanol-water was optimized in order to recover high quality lignin from rice-straw previously pre-treated by autohydrolysis at 210 °C. The results showed a selective and appreciable removal of lignin under very mild conditions and the highest delignification yield occurred at 30 °C. The lignin extracts were characterised using capillary zone electrophoresis (CZE), size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FT-IR) and 31P-NMR, and two-dimensional heteronuclear single quantum correlation NMR spectroscopy (2D-HSQC NMR), which enabled the identification of low molecular weight lignins with a syringyl/guaiacyl ratio of about 0.74 containing phenolic compounds with potential bioactive properties. In order to separate the target compounds, membrane technology has been used and an enriched extract containing value-added phenolic compounds such as tricin, vanillin, ferulic acid and p-coumaric acid was obtained. High membrane efficiency (around 80%) was obtained for target compounds.