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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.
- 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.