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- Current pretreatment technologies for the development of cellulosic ethanol and biorefineriesPublication . Silveira, Marcos H. Luciano; Morais, Ana Rita C.; Lopes, André; Olekszyszen, Drielly Nayara; Lukasik, Rafal M.; Andreaus, Jurgen; Ramos, Luiz PereiraLignocellulosic materials, such as forest, agriculture, and agroindustrial residues, are among the most important resources for biorefineries to provide fuels, chemicals, and materials in such a way to substitute for, at least in part, the role of petrochemistry in modern society. Most of these sustainable biorefinery products can be produced from plant polysaccharides (glucans, hemicelluloses, starch, and pectic materials) and lignin. In this scenario, cellulosic ethanol has been considered for decades as one of the most promising alternatives to mitigate fossil fuel dependence and carbon dioxide accumulation in the atmosphere. However, a pretreatment method is required to overcome the physical and chemical barriers that exist in the lignin–carbohydrate composite and to render most, if not all, of the plant cell wall components easily available for conversion into valuable products, including the fuel ethanol. Hence, pretreatment is a key step for an economically viable biorefinery. Successful pretreatment method must lead to partial or total separation of the lignocellulosic components, increasing the accessibility of holocellulose to enzymatic hydrolysis with the least inhibitory compounds being released for subsequent steps of enzymatic hydrolysis and fermentation. Each pretreatment technology has a different specificity against both carbohydrates and lignin and may or may not be efficient for different types of biomasses. Furthermore, it is also desirable to develop pretreatment methods with chemicals that are greener and effluent streams that have a lower impact on the environment. This paper provides an overview of the most important pretreatment methods available, including those that are based on the use of green solvents (supercritical fluids and ionic liquids).
- Industry-based biorefineriesPublication . Cabrita, Isabel; Carvalheiro, Florbela; Duarte, Luís C.; Gírio, Francisco; Lukasik, Rafal M.
- Imidazole processing of wheat straw and eucalyptus residues: comparison of pre-treatment conditions and their influence on enzymatic hydrolysisPublication . Pereira, Pedro M. A.; Bernardo, Joana; Roseiro, Luisa B.; Gírio, Francisco; Lukasik, Rafal M.ABSTRACT: Biomass pre-treatment is a key step in achieving the economic competitiveness of biomass conversion. In the present work, an imidazole pre-treatment process was performed and evaluated using wheat straw and eucalyptus residues as model feedstocks for agriculture and forest-origin biomasses, respectively. Results showed that imidazole is an efficient pre-treatment agent; however, better results were obtained for wheat straw due to the recalcitrant behavior of eucalyptus residues. The temperature had a stronger effect than time on wheat straw pre-treatment but at 160 degrees C and 4 h, similar results were obtained for cellulose and hemicellulose content from both biomasses (ca. 54% and 24%, respectively). Lignin content in the pre-treated solid was higher for eucalyptus residues (16% vs. 4%), as expected. Enzymatic hydrolysis, applied to both biomasses after different pre-treatments, revealed that results improved with increasing temperature/time for wheat straw. However, these conditions had no influence on the results for eucalyptus residues, with very low glucan to glucose enzymatic hydrolysis yield (93% for wheat straw vs. 40% for eucalyptus residues). Imidazole can therefore be considered as a suitable solvent for herbaceous biomass pre-treatment.
- Selective recovery of phenolic compounds and carbohydrates from carob kibbles using water-based extractionPublication . Almanasrah, Mohammad; Roseiro, Luisa B.; Lukasik, Rafal M.; Carvalheiro, Florbela; Brazinha, Carla; Crespo, João; Kallioinen, Mari; Manttari, Mika; Duarte, Luís C.Carob kibbles are an important renewable source of valuable compounds, such as fermentable sugars and phenolic compounds. However, the selective recovery of these compounds is not a trivial task. In this work, a strategy was developed to enable the recovery of both classes of compounds by means of awater-based extraction.One-step extraction recovered only approximately 20% of the phenolic compounds, corresponding to an extraction yield of 0.6 g Gallic acid equivalents (GAE)/100 g dry mass of carob kibbles. The obtained extract contained a significant amount of carbohydrates (110 g/L). The alternative two-step extraction developed enabled higher compound selectivity together with an increase in the yield of the phenolic compounds to about 70%, corresponding to 1.9 gGAE/100 g carob dry matter.The two-step extraction was easily scaled-up and is an effective method to obtain significantly sepa-rated carbohydrates and polyphenol-rich streams that can be further processed, e.g., in biorefineries orfood industries, respectively.
- Economic, social and environmental impacts attained by the use of the effluents generated within a small-scale biorefinery conceptPublication . Lopes, Tiago; Lukasik, Rafal M.ABSTRACT: Biorefineries are emerging as the proper route to defeat climate change and other social, socio-economic and environmental concerns. So far, no residual lignocellulosic biomass-based biorefineries have been yet industrially implemented, mainly due to its economic viability. This article exposes some elements that may help overcome the bottlenecks associated to its social, economic and environmental sustainability: small-scale approaches, biomass valorisation through added-value products and near-zero effluent.
- Sustainable approach of high-pressure agave bagasse pretreatment for ethanol productionPublication . Aguirre-Fierro, Arelí; Ruiz, Héctor A.; Cerqueira, Miguel A.; Ramos-González, Rodolfo; Rodríguez-Jasso, Rosa M.; Marques, Susana; Lukasik, Rafal M.ABSTRACT: Agave bagasse is one of the most abundant lignocellulosic residues readily available for valorization. The agave bagasse was pretreated by applying high-pressure CO2–H2O mixture at temperatures ranging from 150 to 190 °C for a residence time varying from 10 to 50 min. Subsequently, solid phase obtained from pretreatment was subject to enzymatic hydrolysis at high solid loadings. Under optimal conditions, the process integrating pretreatment followed by enzymatic hydrolysis yielded 75.8 mol% of the polysaccharides present in the biomass converted into oligo- or monosaccharides, providing 110.5 g/L of reducing sugars. The monosaccharides present in the obtained hydrolysate were successfully fermented into ethanol, demonstrating the feasibility of performing its biological conversion to commercial biofuels or biochemicals. Thereby, the present study has demonstrated the proof of concept of use of more sustainable high-pressure CO2–H2O pretreatment in the context of lignocellulosic residual biomass valorization based on the biochemical sugar platform.
- Biodegradable ionic liquids in service of biomass upgradePublication . Piedade, Patrícia J.; Kochanska, Ewa; Lukasik, Rafal M.ABSTRACT: This work presents an up-to-date overview of the use of biodegradable ionic liquids in the conversion of biomass in the context of biorefineries. Special attention is given to works in which biodegradability potentiates advanced application of ionic liquids in terms of process intensification for deployment of technologies towards bioenergy carriers or bioderived valueadded products.
- The green biorefinery concept for the valorisation of pistachio shell by high-pressure CO2/H2O systemPublication . Özbek, Hatice Neval; Fockink, Douglas, H.; Yanik, Derya Koçak; Gögüs, Fahrettin; Lukasik, Rafal M.ABSTRACT: The use of high-pressure CO2/H2O in valorisation of pistachio shell to produce hemicellulose-derived, oligomeric and monomeric sugars and their further transformation to furfural as well as enzymatic transformation of cellulose-rich solids is presented in this work. Different pre-treatment conditions i.e. temperature ranged from 160 to 200 degrees C; reaction time varied between 0 and 30 min and liquid to solid mass ratio between 4 and 8 with constant initial pressure of CO2 of 50 bars were examined. At the optimal pre-treatment conditions, the concentrations of xylose and xylo-oligosaccharide were of 1.7 and 35.5 g/L. Furthermore, this work demonstrates the high-pressure CO2 catalysed production of furfural in an aqueous/tetrahydrofuran system. For model solution containing a mixture of xylose and acetic acid, the optimised furfural yield was as high as 53.3 mol%, while for real sample of hemicellulose hydrolysate, the furfural yield of 39.6 mol% and the selectivity of 40.0 mol% were obtained. Additionally, quantitative glucan to glucose conversion by enzymatic hydrolysis of pre-treated cellulose-rich biomasses was achieved.
- Desenvolvimento de processos de pré-tratamento da biomassa para a separação eficiente das correntes de lenhina e de açúcaresPublication . Carvalheiro, Florbela; Lukasik, Rafal M.; Duarte, Luís C.; Roseiro, Luisa B.; Ribeiro, Belina; Marques, Susana; Bernardo, Joana; Van-Dúnem, Vanmira; Pires, Filipa; Costa, Diogo; Sanfins, Luís; Gírio, FranciscoRESUMO: O fracionamento da biomassa é um dos principais pontos críticos no desenvolvimento das biorrefinarias. Neste trabalho, são apresentadas três estratégias inovadoras com vista à separação seletiva das frações de celulose, hemicelulose e lenhina, utilizando compostos orgânicos, geralmente em solução aquosa: i) utilização de líquidos iónicos (ILs) em particular [emim][OAc] e [emim][HSO4]); ii) processos organosolv baseados na utilização de misturas etanol:água (50:50); e iii) um processo não aquoso baseado em imidazole. Os processos com ILs permitiram um fracionamento diferencial e, em geral, uma redução da cristalinidade da celulose. Os processos organosolv permitiram modular a distribuição de produtos derivados da hemicelulose e da lenhina entre as fases sólida e líquida. A utilização de imidazole, permitiu a separação das duas frações de polissacáridos e contribuiu para despolimerização da lenhina.
- Biorefinery approach for lignocellulosic biomass valorisation with an acidic ionic liquidPublication . Lopes, André; Lins, Roberto M. G.; Rebelo, Ricardo A.; Lukasik, Rafal M.ABSTRACT: The commercialisation of the biorefinery approach involving the integration of the multi-step valorisation of low value biomass feedstock into a variety of chemicals, fuels and bioproducts is still very limited. In this context, the present work proposes an advanced methodology that comprises a cascaded approach towards wheat straw valorisation. The studied concept lies in the employment of an aqueous solution of the acidic 1-ethyl-3-methylimidazolium hydrogen sulfate ionic liquid in a selective and efficient hydrolysis of the hemicellulose fraction of wheat straw into pentoses, namely xylose and arabinose. An experimental design was utilised to search for the optimisation parameters, resulting in a maximum 80.5 wt% pentose yield in the liquor. Furthermore, the remaining solid, which contained practically all of the initial cellulose and lignin, was processed by considering two scenarios: (i) a direct enzymatic hydrolysis of the reaction solid, which yielded 75.8 mol% glucose; or (ii) a preceding extraction of lignin followed by enzymatic saccharification of the cellulose pulp, which yielded 91.3 mol% glucose. For both scenarios, lignin-rich solid fractions were obtained with distinct purities and yields. Additionally, the second scenario allowed producing a stream of value-added aromatic (phenolic) compounds. This work also overcame the challenges in IL recycling and reuse, with a simultaneous recovery of the pentoses from the reaction liquor as high as 88.6 mol%.