Abstract
A shift to a bioeconomy development model has been evolving, conducting the scientific community to investigate new ways of producing chemicals, materials and fuels from renewable resources, i.e., biomass. Specifically, technologies that provide high performance and maximal use of biomass feedstocks into commodities with reduced environmental impact have been highly pursued. A key example comprises the extraction and/or dissolution of polysaccharides, one of the most abundant fractions of biomass, which still need to be improved regarding these processes’ efficiency and selectivity parameters. In this context, the use of alternative solvents and the application of less energy-intensive processes in the extraction of polysaccharides might play an important role to reach higher efficiency and sustainability in biomass valorization. This review debates the latest achievements in sustainable processes for the extraction of polysaccharides from a myriad of biomass resources, including lignocellulosic materials and food residues. Particularly, the ability of ionic liquids (ILs) and deep eutectic solvents (DESs) to dissolve and extract the most abundant polysaccharides from natural sources, namely cellulose, chitin, starch, hemicelluloses and pectins, is scrutinized and the efficiencies between solvents are compared. The interaction mechanisms between solvent and polysaccharide are described, paving the way for the design of selective extraction processes. A detailed discussion of the work developed for each polysaccharide as well as the innovation degree and the development stage of dissolution and extraction technologies is presented. Their advantages and disadvantages are also identified, and possible synergies by integrating microwave- and ultrasound-assisted extraction (MAE and UAE) or a combination of both (UMAE) are briefly described. Overall, this review provides key information towards the design of more efficient, selective and sustainable extraction and dissolution processes of polysaccharides from biomass.
Highlights
The increased interest and need for sustainable growth of the world population as well as the concerns related to massive pollution and climate changes have led to switch the paradigm of a fossil-based economy to a sustainable bio-based model of development
A review regarding the potentialities of green solvents, namely ionic liquids (ILs) and deep eutectic solvents (DESs), for polysaccharides dissolution and extraction from biomass, i.e., lignocellulosic biomass and food waste, was presented
There are advantages in using ILs and DESs instead of volatile and non-environmentally friendly organic solvents or harsh acidic/alkaline solutions usually applied for polysaccharides dissolution and extraction
Summary
The increased interest and need for sustainable growth of the world population as well as the concerns related to massive pollution and climate changes have led to switch the paradigm of a fossil-based economy to a sustainable bio-based model of development. Lignocellulosic biomass represents the most abundant source of renewable feedstocks with an approximate production of 1.1 × 1011 tons/year, consisting of non-edible plant materials, such as woody trees, shrubs and grasses [5,6], produced by forestry and agricultural sectors The composition of this biomass varies with several factors but it is mainly composed of polysaccharides, such as cellulose, hemicelluloses, starch and lignin, as well as, in smaller amounts, of other components like proteins and extractives such as terpenes, sterols, phenolics and fatty acids, among many others [7]. The size, morphology and composition of these granules vary with the biomass source as well as with the isolation method [50] Both amylose and amylopectin are composed of glucose units linked by glycosidic α(1→4) bonds, with amylopectin being slightly branched and presenting α(1→6) linkages.
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