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Autohydrolysis of Annona cherimola Mill. seeds: optimization, modeling and products characterization

Publication . Branco, Pedro C.; Dionísio, Ana; Ivone, Torrado; Carvalheiro, Florbela; Castilho, Paula C.; Duarte, Luís C.

Annona cherimola Mill. seeds are a residue of the industrial processing of this fruit, for which, presently, there is no industrial application. They have a considerable amount of oil, which can be converted into biodiesel, but the remaining lignocellulosic fraction still needs relevant added-value valorization routes. In this work, the selective hemicelluloses removal by autohydrolysis was optimized aiming to maximize the yield of oligosaccharides with potential applications in food, pharmaceutical and cosmetic industries. A maximum of 10.4 g L-1 of oligosaccharides was obtained, for a severity factor of 3.6, where 74.5% of the original hemicellulose was solubilized. The process kinetics is presented, modeled (based on the Arrhenius equation) and its scale-up is discussed. The hydrolyzate shelf-life was evaluated and the produced oligosaccharides are stable at room temperature for, at least, 3 weeks. Furthermore, all oligosaccharides are also stable at 100 °C for 1 h, in pH values between 1 and 11, enabling their industrial processing, and at 37 °C for 3 h, in pH values between 1 and 3, thus indicating its potential classification as non-digestible oligosaccharides. The remaining cellulose enriched solids presented an increased enzymatic digestibility (as a function of the autohydrolysis severity) that assures its efficient use in subsequent processes (e.g., bioethanol production). The upgrade route developed in this work in combination to the previously reported use of A. cherimola seed oil for biodiesel production can lead to an integrated zero-waste valorization strategy within the biorefinery framework.

2015Journal article

Open access

Hydrothermal pretreatment of several lignocellulosic mixtures containing wheat straw and two hardwood residues available in Southern Europe

Publication . Silva-Fernandes, Talita; Duarte, Luís C.; Carvalheiro, Florbela; Loureiro-Dias, M. Conceição; Fonseca, César; Gírio, Francisco

This work studied the processing of biomass mixtures containing three lignocellulosic materials largely available in Southern Europe, eucalyptus residues (ER), wheat straw (WS) and olive tree pruning (OP). The mixtures were chemically characterized, and their pretreatment, by autohydrolysis, evaluated within a severity factor (log R0) ranging from 1.73 up to 4.24. A simple modeling strategy was used to optimize the autohydrolysis conditions based on the chemical characterization of the liquid fraction. The solid fraction was characterized to quantify the polysaccharide and lignin content. The pretreatment conditions for maximal saccharides recovery in the liquid fraction were at a severity range (log R0) of 3.65–3.72, independently of the mixture tested, which suggests that autohydrolysis can effectively process mixtures of lignocellulosic materials for further biochemical conversion processes.

2015Journal article

Open access

Fractionation of hemicelluloses and lignin from rice straw by combining autohydrolysis and optimised mild organosolv delignification

Publication . Moniz, Patricia; Lino, João; Duarte, Luís C.; Roseiro, Luisa B.; Boeriu, Carmen G.; Pereira, Helena; Carvalheiro, Florbela

An 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.

2015Journal article

Open access