Cellulose oligomers production and separation for the synthesis of new fully bio-based amphiphilic compounds

Bottom-Up Synthesized Glucan Materials: Opportunities from Applied Biocatalysis

Linear d-glucans are natural polysaccharides of simple chemical structure. They are comprised of d-glucosyl units linked by a single type of glycosidic bond. Noncovalent interactions within, and between, the d-glucan chains give rise to a broad variety of macromolecular nanostructures that can assemble into crystalline-organized materials of tunable morphology. Structure design and functionalization of d-glucans for diverse material applications largely relies on top-down processing and chemical derivatization of naturally derived starting materials. The top-down approach encounters critical limitations in efficiency, selectivity, and flexibility. Bottom-up approaches of d-glucan synthesis offer different, and often more precise, ways of polymer structure control and provide means of functional diversification widely inaccessible to top-down routes of polysaccharide material processing. Here the natural and engineered enzymes (glycosyltransferases, glycoside hydrolases and phosphorylases, glycosynthases) for d-glucan polymerization are described and the use of applied biocatalysis for the bottom-up assembly of specific d-glucan structures is shown. Advanced material applications of the resulting polymeric products are further shown and their important role in the development of sustainable macromolecular materials in a bio-based circular economy is discussed.

Facile preparation of near-monodisperse oligocellulose and its elastomeric derivatives with tunable mechanical properties

Oligocellulose (OC) with low polydispersity indices has been produced in large quantities using an improved method of acid-assisted hydrolysis, in which long cellulose chains disintegrate in concentrated phosphoric acid at moderately elevated temperatures. The hydrolysis time has been reduced by three orders of magnitude without compromising the overall yield of the process or the quality of OC products. The efficient production of high-quality OCs in large quantities allows for developing OC-derived elastomeric materials. A series of OC-graft-poly(isobornyl methacrylate-random-n-butyl acrylate) [OC-g-P(IBOMA-r-BA)] elastomers have been synthesized via activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP). OC-g-P(IBOMA-r-BA) elastomers have tunable molecular architectures and phase morphologies toward desirable mechanical properties and thermal stability suitable for various applications. The methodologies of the OC production and the graft-polymers synthesis in this study would help advance technologies for broader applications of bio-based elastomers.

Insights to improve the activity of glycosyl phosphorylases from Ruminococcus albus 8 with cello-oligosaccharides

The phosphorolysis of cello-oligosaccharides is a critical process played in the rumen by Ruminococcus albus to degrade cellulose. Cellodextrins, made up of a few glucosyl units, have gained lots of interest by their potential applications. Here, we characterized a cellobiose phosphorylase (RalCBP) and a cellodextrin phosphorylase (RalCDP) from R. albus 8. This latter was further analyzed in detail by constructing a truncated mutant (Ral∆N63CDP) lacking the N-terminal domain and a chimeric protein by fusing a CBM (RalCDP-CBM37). RalCBP showed a typical behavior with high activity on cellobiose. Instead, RalCDP extended its activity to longer soluble or insoluble cello-oligosaccharides. The catalytic efficiency of RalCDP was higher with cellotetraose and cellopentaose as substrates for both reaction directions. Concerning properties of Ral∆N63CDP, results support roles for the N-terminal domain in the conformation of the homo-dimer and conferring the enzyme the capacity to catalyze the phosphorolytic reaction. This mutant exhibited reduced affinity toward phosphate and increased to glucose-1-phosphate. Further, the CBM37 module showed functionality when fused to RalCDP, as RalCDP-CBM37 exhibited an enhanced ability to use insoluble cellulosic substrates. Data obtained from this enzyme's binding parameters to cellulosic polysaccharides agree with the kinetic results. Besides, studies of synthesis and phosphorolysis of cello-saccharides at long-time reactions served to identify the utility of these enzymes. While RalCDP produces a mixture of cello-oligosaccharides (from cellotriose to longer oligosaccharides), the impaired phosphorolytic activity makes Ral∆N63CDP lead mainly toward the synthesis of cellotetraose. On the other hand, RalCDP-CBM37 remarks on the utility of obtaining glucose-1-phosphate from cellulosic compounds.

Solvent-Assisted Fractionation of Oligomeric Cellulose and Reversible Transformation of Cellulose II and IV

Oligomeric cellulose with an average degree of polymerization of 7.68 and a polydispersity of 1.04 has been fractionated using solution processes. Three fractions have been obtained through initial dissolution, subsequent crystallization, and solvent precipitation, respectively. The resulting oligocellulose fraction has an average degree of polymerization of 7.70 and a polydispersity of 1.01, respectively. Cellulose IV₂ crystals form in the oligocellulose fraction, and reversibly transform to II and back to IV using simple solvents.

ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016

This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.

Cello-oligosaccharides production from lignocellulosic biomass and their emerging prebiotic applications

Cello-oligosaccharides (COS) are linear oligosaccharides composed of β-1,4-linked glucopyranose units. They comprise a group of important new oligosaccharides of significant interest and potential applications in the pharmaceutical, food, chemical, and feed industries, currently emerging as potential prebiotic compounds. COS from lignocellulosic biomass, specifically the agro-industrial residues and by-products of the forestry industry, constitute a new attractive process that imposes the sustainable use of biomass resources. Two main strategies have been used for the production of COS: acid-based and enzyme-based cellulose hydrolysis. The latter has been considered more attractive due to the use of milder reaction conditions and less production of monomers. This review summarizes that although COS is emerging as a potential prebiotic with also other potential applications, there is a lack of information regarding the large-scale production, which could be associated with the recalcitrant nature of cellulose compared to other polysaccharides, which hinders the hydrolysis of its dense network.

Possible dissolution mechanism of alkali lignin in lactic acid-choline chloride under mild conditions

In this study, several representative deep eutectic solvents (DESs) were designed to evaluate the solubility for alkali lignin (AL). It was found that DESs with lactic acid (LA) as hydrogen bond donors (HBDs) had good solubility for AL, in which lactic acid(LA) : choline chloride(ChCl) 10 : 1 showed excellent solubility with more than 17 wt% under a relatively mild condition of 60 °C. The results of gel permeation chromatography (GPC), FTIR and ¹H and HSQC NMR spectroscopies revealed an important possible dissolution mechanism of AL in LA-ChCl, that is, AL could be depolymerized under the action of LA when dissolved in LA-ChCl. Then, a new connection would form between the phenolic groups on the lignin fragments and ChCl, which is similar to that between ChCl and LA in DES, leading to an increase in the molecule weight of lignin. The new connections could be easily broken under the action of heat (150 °C) or microwave to the redispersion of lignin fragments. The results would provide a theoretic base for the high-value application of lignin in bioresources.

In this study, several representative deep eutectic solvents (DESs) were designed to evaluate the solubility for alkali lignin (AL).

Structural characterization and comparison of enzymatic and deep eutectic solvents isolated lignin from various green processes: Toward lignin valorization

In this work, several representative green processes were developed to extract the enzymatic lignin and deep eutectic solvents (DESs) isolated lignin from corn straw. The results revealed that enzymatic lignin and DESs isolated lignin had a relatively low and homogeneous molecular weight and DESs isolated lignin shown a higher purity. Enzymatic and DESs isolated lignin showed good representativeness and similar to original herbal lignin structures accompany few aryl ether linkage cleavages and oxidation phenomenon. Among them, the subcritical CO₂-assisted autohydrolysis and ChCl/Lac DESs treatment exhibited a higher severity for lignin preparation, and sequence DESs isolated lignin had a better reactivity. The β-O-4 ether bonds and carbon-carbon bonds linkage were further broken up during the Lac and DESs sequence treatment. In short, the described processes showed practical significance for lignin extraction and potential valorization, as well as help to develop more novel strategies for the current biorefinery process.