Cellobiose Units Research Articles

Discovery of novel cellobiose lipid gene clusters from Basidiomycetes: How chemical variation is reflected in gene cluster architecture.

Cellobiose lipids are surface-active compounds or biological detergents produced by distinct Basidiomycetes yeasts, of which the most and best-described ones belong to the Ustilaginomycetes class. The molecules display slight variation in congener type, which is linked to the hydroxylation position of the long fatty acid, acetylation profile of the cellobiose unit, and presence or absence of the short fatty acid. In general, this variation is strain specific. Although cellobiose lipid biosynthesis has been described for about 11 yeast species, hitherto only two types of biosynthetic gene clusters are identified, and this for only three species. This work adds six more biosynthetic gene clusters and describes for the first time a novel type of cellobiose lipid biosynthetic cluster with a simplified architecture related to specific cellobiose lipids synthesized by Trichosporonaceae family members.

Batch and continuous adsorption of Cd(II) and Pb(II) on polycarboxylated sugarcane bagasse

A bioadsorbent composed of polycarboxylated sugarcane bagasse (PSB) was prepared in a one-step reaction by the esterification of sugarcane bagasse hydroxyl groups with butane-1,2,3,4-tetracarboxylic dianhydride. 13C SS NMR measurements showed that 0.3 butane-1,2,3,4-tetracarboxylic acid units were grafted per cellobiose unit. PSB was used in the batch adsorption of Cd(II) and Pb(II) from mono-, bi-, and multicomponent aqueous solutions. For upscaling of the technology aiming at practical applications, evaluation was made of 4 cycles of continuous adsorption of Cd(II) and Pb(II) on PSB in a fixed-bed column. The maximum adsorption capacities for Cd(II) and Pb(II) on PSB in batch and continuous modes were 0.55 and 1.164 mmol g−1 (62 and 241.2 mg g−1), and 0.58 and 0.71 mmol g−1 (65 and 153 mg g−1), respectively. The standard adsorption enthalpy change (ΔadsH°) values for Cd(II) and Pb(II) were 8.6 ± 0.5 and − 0.28 ± 0.03 kJ mol−1, respectively. The interactions involved in the adsorption of Cd(II) and Pb(II) on PSB were investigated. Multicomponent studies showed that Pb(II) and Cd(II) acted to suppress the adsorption of each other. In the presence of Cu(II) and Zn(II), the adsorption capacity followed the order: Pb(II) > Cu(II) > Cd(II) > Zn(II). Batch and continuous adsorption-desorption studies showed that PSB could be reused in at least 4 successive cycles, with desorption efficiencies of 88–100 %, which is essential for minimizing waste generation and reducing process costs.

Synthesis and application of an unprecedented bioadsorbent for removing arsenic from aqueous systems

A quaternary ammonium anion exchanger (SBTEA) was prepared from sugarcane bagasse (SB) employing an improved two-step synthesis method by chemical modification with epichlorohydrin (EPI) and triethylamine (TEA) using N,N-dimethylformamide as a solvent without catalyst. Two multivariate optimizations were utilized to determine optimum conditions for SBTEA synthesis using Doehlert experimental designs. The optimum synthesis conditions were: VEPI = 12.8 mLgSB−1; VTEA = 22.0 mLgSB−1; and T1 (etherification step) = T2 (amination step) = 100 °C. The chlorine and nitrogen contents of the SBTEA produced under these conditions with a 21-fold increase in the synthesis scale (SBTEA-LS) were 4.2 ± 0.1% and 1.485 ± 0.007%, respectively. The 13C Multi-CP SS NMR revealed that 1.7 quaternary ammonium groups were introduced for 10 cellobiose units. SBTEA-LS was used to remove As(V) from contaminated groundwater samples with high removal efficiency (95 ± 4%), even with strong competitors such as SO42−. The interactions involved in the adsorption were investigated through macroscopic and microscopic measurements, which suggested that the adsorption of As(V) on SBTEA-LS occurred mainly by ion exchange. Desorption experiments proved that SBTEA-LS could be efficiently regenerated (Edes > 90%) using an HNO3 solution, reducing operating costs and favoring technology upscaling.

Noble metal nanoparticles dispersed on nanocellulose: a green platform for catalytic organic transformations

In recent years, plant-derived biomaterials, typically cellulose, acting as catalytic supports have a great impact on heterogeneous catalysis thanks to their biodegradability, non-toxicity, low-cost, availability and easy-implementation. As the most abundant biopolymer found in nature, cellulose consists of repeating cellobiose units which are built up from two anhydroglucose rings and linked by a β-1,4 glycosidic bond. The term of “nanocellulose” has been widely used to describe cellulose nano-objects, involving cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs) and bacterial cellulose (BC). Nanocellulose features high specific surface area and controllable surface chemistry, high crystalline structure, superior mechanical strength and thermal stability, resulting in its applications in food, cosmetics, pharmaceutical, biomedical and paper industries. Concerning to catalytic support application, the nanocellulose surface possesses the hydroxyl (in nature) or the sulfate ester groups (modified via acid hydrolysis), facilitating metal ions reduction towards the corresponding metal nanoparticles. In addition, the supramolecular structure of cellulose permits to disperse metal nanoparticles and prevent their agglomerations. In this context, nanocellulose is introduced as matrices for immobilizing noble metal nanoparticles and then applied to catalytic organic transformations.

Elongated Rodlike Particle Formation of Methyl Cellulose in Aqueous Solution.

The conformation and structure of methyl cellulose (MC) ether samples dissolved in pure water under dilute conditions were carefully reconsidered based on the results obtained using small-to-wide-angle neutron scattering (S-WANS), static light scattering (SLS), dynamic light scattering (DLS), and viscometric techniques. The examined MC samples possessed an average degree of substitution by methyl groups per glucose unit of ca 1.8 and weight average molar masses (Mw), ranging from 23 to 790 kg mol–1. S-WANS experiments clearly demonstrated that the samples possess highly elongated rigid rodlike local structures in deuterium oxide solutions with weak periodicities of ca 0.4 and 1.0 nm on a length scale, which correspond to the average intermolecular distance between molecular chain portions facing each other in the formed rodlike structure and the repeating length of the monomeric cellobiose unit of molecular chains, respectively. Ratios of the particle length (L) to the radius of gyration (Rg) determined by SLS techniques approximately showed the relationship LRg–1 = holding in rigid rods over the entire Mw range examined in this study. However, the folding number, defined as the ratio of the average molecular contour length (l) to L, remained at the value of lL–1 ∼ 2, representing an elongated one-folded hairpin structure, until Mw ∼ 300 kg mol–1 and increased substantially up to ca 4.9 at the highest Mw of 790 kg mol–1. The observed increase in the lL–1 value corresponded well with an increase in the diameter of the formed rod with increasing Mw observed in the S-WANS data. The Mw dependencies of the translational diffusion coefficient determined via DLS measurements and that of the intrinsic viscosity detected via viscometric techniques also distinctly demonstrated that particles formed by the MC samples dissolved in aqueous solution behave as elongated rigid rods irrespective of Mw.

DFT studies on the physicochemical properties of a new potential drug carrier containing cellobiose units and its complex with paracetamol

DFT studies on the physicochemical properties of a new potential drug carrier containing cellobiose units and its complex with paracetamol

Nanoscale dynamics of cellulose digestion by the cellobiohydrolase TrCel7A

Understanding the mechanism by which cellulases from bacteria, fungi, and protozoans catalyze the digestion of lignocellulose is important for developing cost-effective strategies for bioethanol production. Cel7A from the fungus Trichoderma reesei is a model exoglucanase that degrades cellulose strands from their reducing ends by processively cleaving individual cellobiose units. Despite being one of the most studied cellulases, the binding and hydrolysis mechanisms of Cel7A are still debated. Here, we used single-molecule tracking to analyze the dynamics of 11,116 quantum dot-labeled TrCel7A molecules binding to and moving processively along immobilized cellulose.

Nanoscale dynamics of cellulose digestion by the cellobiohydrolase TrCel7A

Understanding the mechanism by which cellulases from bacteria, fungi, and protozoans catalyze the digestion of lignocellulose is important for developing cost-effective strategies for bioethanol production. Cel7A from the fungus Trichoderma reesei is a model exoglucanase that degrades cellulose strands from their reducing ends by processively cleaving individual cellobiose units. Despite being one of the most studied cellulases, the binding and hydrolysis mechanisms of Cel7A are still debated. Here, we used single-molecule tracking to analyze the dynamics of 11,116 quantum dot-labeled TrCel7A molecules binding to and moving processively along immobilized cellulose. Individual enzyme molecules were localized with a spatial precision of a few nanometers and followed for hundreds of seconds. Most enzyme molecules bound to cellulose in a static state and dissociated without detectable movement, whereas a minority of molecules moved processively for an average distance of 39 nm at an average speed of 3.2 nm/s. These data were integrated into a three-state model in which TrCel7A molecules can bind from solution into either static or processive states and can reversibly switch between states before dissociating. From these results, we conclude that the rate-limiting step for cellulose degradation by Cel7A is the transition out of the static state, either by dissociation from the cellulose surface or by initiation of a processive run. Thus, accelerating the transition of Cel7A out of its static state is a potential avenue for improving cellulase efficiency.

A TEMPO-catalyzed oxidation–reduction method to probe surface and anhydrous crystalline-core domains of cellulose microfibril bundles

A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD4 to 6-deutero- and 6,6-dideuteroglucosyl units, provided a robust method for determining relative proportions of disordered amorphous, ordered surface chains, and anhydrous core-crystalline residues of cellulose microfibrils inaccessible to TEMPO. Both glucosyl residues of cellobiose units, digested from amorphous chains of cellulose with a combination of cellulase and cellobiohydrolase, were deuterated, whereas those from anhydrous chains were undeuterated. By contrast, solvent-exposed and anhydrous residues alternate in surface chains, so only one of the two residues of cellobiosyl units was labeled. Although current estimates indicate that each cellulose microfibril comprises only 18 to 24 (1 → 4)-β-d-glucan chains, we show here that microfibrils of walls of Arabidopsis leaves and maize coleoptiles, and those of secondary wall cellulose of cotton fibers and poplar wood, bundle into much larger macrofibrils, with 67 to 86% of the glucan chains in the anhydrous domain. These results indicate extensive bundling of microfibrils into macrofibrils occurs during both primary and secondary wall formation. We discuss how, beyond lignin, the degree of bundling into macrofibrils contributes an additional recalcitrance factor to lignocellulosic biomass for enzymatic or chemical catalytic conversion to biofuel substrates.

Kanamycin complexation with cellulose acetate sulphate: a promissing way from injectable to oral form of antibiotic

Water-insoluble polyelectrolyte complexes of cellulose acetate sulphate in the form of sodium salt (Na-CAS) and aminoglycoside antibiotic (AB) kanamycin (KAN) were obtained by mixing of the components aqueous solutions. The composition of the complexes was determined in accordance with the medium pH and mixing order. The increase of Na‑CAS cellobiose units per mole of AB has been shown to correlate with the decrease of pH value. The complex formation was studied by Fourier transform infrared spectroscopy, thermal analysis, X-ray analysis, laser diffraction, motion trajectory of nanoparticles analysis and scanning electron microscopy. Quantum-chemical study of the relative stability of the protonated forms of KAN in aqueous solution was performed to determine the preferred protonation sites of KAN molecule. The pKa values of KAN were calculated by means of isodesmic reactions method. The structures and binding energy for the KAN dimer and the KAN – CAS complex were also investigated by quantum-chemical methods. Na‑CAS – KAN complex itself and immobilised on the activated carbon was shown to demonstrate in vitro two times antibacterial activity of the standard (injectable) form of KAN against Mycobacterium tuberculosis. It can be recommended for in vivo clinical trials as a new form of aminoglycoside AB for oral administration.

Pretreatment of sugarcane bagasse by OX‐B to enhancing the enzymatic hydrolysis for ethanol fermentation

AbstractThe main by‐product of the alcohol industry is the sugarcane bagasse, which can be used to produce second generation ethanol. Studies about pretreatment technologies are increasingly greater, a fundamental step for the efficient this fuel production. The reagents and wastewater treatment costs are still a bottleneck for this type of technology. The present work aimed to study the pretreatments of sugarcane bagasse using a highly oxidative solution Ox‐B. In this study we used high solids loadings, aimed at reducing the use of reagent and the water consumption. We carried out an experimental design 32 for the pretreatment step. The pretreated material followed an enzymatic hydrolysis with 10% (m/v) loading, and enzymatic loading of 15 Filter Paper Units (FPU)/g and 25 cellobiose units (CBU)/g of bagasse. For the best pretreatment condition the desirability tool showed the best pretreatment condition for the release of glucose as 20% solids, 25°C and 2 h, achieving 251.94 mg of glucose per gram of raw bagasse. However, the maximum ethanol yield was 70%, that possible was affected by the presence of chlorine in the pre‐treated mass that has been affected the fermentation process. In general, Ox‐B proved to be a potential pretreatment agent for sugarcane bagasse.Practical ApplicationsSugarcane bagasse is a residual material which can be used for second‐generation (2G) bioethanol production. In this study, Ox–B pretreatment of sugarcane bagasse using high solid loadings, both in the pretreatment (20–40% w/v) and the enzymatic hydrolysis (10–20% w/v) stages was conducted in order to reduce reagent usage and consumption of water. The studies will be useful for ethanol production from lignocellulose.

Elucidation of anti-HIV mechanism of sulfated cellobiose–polylysine dendrimers

Three new spherical sulfated cellobiose–polylysine dendrimers of increasing generations bearing negatively charged sulfate groups were prepared by sulfating the corresponding cellobiose–polylysine dendrimers. The first, second, and third-generation derivatives exhibited potent anti-HIV activity with EC50 values of 3.7, 0.6, and 1.5 μg/mL, respectively, in constant to sulfated oligosaccharides with low anti-HIV activity, while the second-generation sulfated dendrimer was the most active. Surface plasmon resonance measurements with poly-l-lysine bearing positively charged amino acids as a model of the HIV surface glycoprotein gp120, indicated that the second-generation dendrimer had the lowest dissociation constant (KD = 1.86 × 10−12 M). Both the particle size and ζ potential increased in the presence of poly-l-lysine. It was proven that the moderate distance between the terminal sulfated cellobiose units in the second-generation dendrimer favored the high anti-HIV activity, owing to the electrostatic interactions developed due to the cluster effect.

High-Resolution Mass Spectrometry Analysis of Reactive Dye Derivatives Removed from Biodegraded Dyed Cotton by Chemical and Enzymatic Methods

The purpose of this study was to determine and characterize the biodegradation of reactive dyes on cotton jersey fabrics buried in soil. Four commonly-used reactive dyes, C.I. Reactive Black 5 (RBlk5), C.I. Reactive Red 198 (RR198), C.I. Reactive Blue 49 (RB49), and C.I. Reactive Orange 35 (RO35), were used in this study. Degradation products were characterized and proposed based on high-performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (HRMS). A chemical method and an enzymatic digestion were developed and used to remove the reactive dye from the control and degraded cotton fabrics. Hydrolyzed reactive dyes and reactive dyes having cellobiose units were synthesized and used as standards for comparison in this study. The possible degradation mechanism pathways of the reactive dyes bonded to cotton fabrics depends on the chemical structure of each dye.

Application of the EF and GH Fragments to the Synthesis of Idraparinux.

A novel total synthesis of fully protected idraparinux has been achieved. A short and efficient protocol for the synthesis of the EF fragment of idraparinux and its C5'-epi analogue (GH unit) has been developed. The same cellobiose unit was transformed in 14 steps into the fully protected EF and GH disaccharide fragments. The key step of this approach is an epimerization of C5 by an elimination-addition sequence leading to l-ido disaccharide (GH unit) with a total yield of 24% (36% for the EF fragment). 1,6-Anhydro ring opening gave suitable substrates for efficient synthesis of fully protected idraparinux. The fully protected antithrombotic pentasaccharide idraparinux was synthesized in 23 steps for the longest linear route, with a 1.7% overall yield from d-cellobiose and d-glucose.

Glucose, not cellobiose, is the repeating unit of cellulose and why that is important

Despite nomenclature conventions of the International Union of Pure and Applied Chemistry and the International Union of Biochemistry and Molecular Biology, the repeating unit of cellulose is often said to be cellobiose instead of glucose. This review covers arguments regarding the repeating unit in cellulose molecules and crystals based on biosynthesis, shape, crystallographic symmetry, and linkage position. It is concluded that there is no good reason to disagree with the official nomenclature. Statements that cellobiose is the repeating unit add confusion and limit thinking on the range of possible shapes of cellulose. Other frequent flaws in drawings with cellobiose as the repeating unit include incorporation of O-1 as the linkage oxygen atom instead of O-4 (the O-1 hydroxyl is the leaving group in glycoside synthesis). Also, n often erroneously represents the number of cellobiose units when n should denote the degree of polymerization i.e., the number of glucose residues in the polysaccharide.

Swollenin from Trichoderma reesei exhibits hydrolytic activity against cellulosic substrates with features of both endoglucanases and cellobiohydrolases

The cellulolytic and hemicellulolytic enzymes of Trichoderma reesei comprise one of the best characterised enzyme systems involved in lignocellulose degradation. In this paper, swollenin (SWOI), a protein recognised based on its sequence similarity with plant expansins, has been characterised. SWOI and its catalytic domain were subjected to analysis of their hydrolytic activity on different soluble carbohydrate polymers. By measuring the production of reducing ends, zymogram-, and viscosity analysis, SWOI was shown to have activity on substrates containing β-1,4 glucosidic bonds, i.e. carboxymethyl cellulose, hydroxyethyl cellulose and β-glucan. The formation of oligosaccharides from β-glucan was analysed by HPLC and showed cellobiose as the main reaction product. SWOI was also able to hydrolyse soluble cello-oligosaccharides and the products formed were all consistent with SWOI cleaving a cellobiose unit off the substrate. In conclusion, the T. reesei swollenin showed a unique mode of action with similarities with action of both endoglucanases and cellobiohydrolases.

Improved pretreatment process using an electron beam for optimization of glucose yield with high selectivity.

In this study, electron beam irradiation (EBI) assisted by a dilute acid pretreatment process was investigated to improve the glucose yield and show high selectivity in the enzymatic hydrolysis of rice straw. In the first step, EBI of rice straw was performed at various doses ranging from 50 to 500kGy. The electron beam-irradiated rice straw was then autoclaved with 3% dilute acid at 120°C for 1h. The pretreated rice straw was finally subjected to enzymatic hydrolysis at 50°C for 24, 48, and 72h by 70 filter paper units (FPU)/mL cellulase and 40 cellobiose units (CbU)/mL glucosidase. Glucose was obtained with a very high selectivity of 92.7% and a total sugar yield of 80% from pretreated rice straw after 72h of enzymatic hydrolysis.

Resistant cellulose-derivative biopolymer templates in natural sepiolite

Sepiolite is a fibrous sheet silicate with a composition of Si12Mg8 (H2O)4(Si6O15)2(OH)4 · 8H2O and has significant physicochemical and rheological properties due to the presence of zeolitic channels in its structure. The highest concentrations of sepiolite worldwide are found in the Madrid Miocene Basin within the edges of saline lakes and are associated with dolomitic and siliceous microbialites. It is remarkable that monomineral sepiolite sediments up to 6 m thick are composed of 6 nm crystallite-sized fibers. The aim of this study is to gather information concerning the organomineralization of sepiolite. The mineral paragenetic sequences associated with this mineral were characterized by XRD in representative samples. The texture was studied by polarized light microscopy and by SEM-, TEM- and HRTEM-EDX. The remains of mineralized biomass are commonly found mixed with sepiolite fibers. Lipidic biomarkers reveal the prevalence of non-branched derivatives of short-chain fatty-acids (C9 to C18), which are characteristic of cyanobacteria and microalgae and support the presence of microorganisms within the studied sediments. The textural organization of sepiolite fibers is similar to the fabric of cellulose fibers produced by microorganisms. There are two types of fiber associations: short and straight fibers ( 10 μm length) forming thin tissues that mimic cellulose and other exopolymers produced by bacteria (for example, acetobacter, cyanobacteria). The similarity is extended to the nanometric scale. Sepiolite is composed of 6 to 10 nm-thick fibers that form mesocrystals (oriented nanocrystal aggregates) that are 50 to 200 nm in length. Based on an XRD analysis of the crystal size distribution, this average fibril thickness is the same as that of cellulose. The growth of sepiolite is limited to the size of cellulose crystallites. The cellobiose unit size is similar to the size of the zeolitic channels of sepiolite (1.04 nm) in the β-[1.4] linkage propagating direction, in which a 180° rotation is produced, as well as to the SiO4 tetrahedra in sepiolite. Its formation is controlled by the orientation and repeating distance of polar groups (OH and derivatives), with numerous defects and disruptions that coincide with amorphous phases of cellulose. The maintenance of polar or ionic characteristics in the organic reticulum and its orientation is essential for the nucleation of sepiolite. This fact makes its recrystallization difficult, which, in turn, proves the high geochemical stability of sepiolite in spite of its nanometric nature.

A sectional approach for biomass: Modelling the pyrolysis of cellulose

We present the adaptation of the sectional model approach to the pyrolysis of cellulose, (C6H10O5)n. Cellulose is the major component of lignocellulosic biomass. Due to its longitudinal structure, cellulose is characterised by one-dimensional chains composed of a varying number of cellobiose molecules, C12H22O11. Fragments of those chains with similar mass are grouped into size classes (BINs) determined by characteristic numbers of cellobiose units. During the pyrolysis of cellulose, reaction temperatures of more than 500K (depending on the heating rate) initiate bond dissociation between cellobiose units. We have developed a new reaction scheme for the pyrolysis of cellulose based on literature models. However, we present the sectional approach as a new concept for modelling the degradation of cellulose. We propose a kinetic data set of A = 2.2 ∙ 1013 s−1 and EA = 225.9 kJ/mol for the dissociation of a single glycosidic bond. Additionally, our model includes the cellobiose devolatilisation to glucose or tars (levoglucosan) including primary gaseous products, the formation of char and water, and secondary gas-phase reactions. Our reactor simulations of cellulose pyrolysis at constant heating rates of 1, 10, 15, and 150 K/min show good agreement with two different experimental data sets.

Crystal Structure and Computational Characterization of the Lytic Polysaccharide Monooxygenase GH61D from the Basidiomycota Fungus Phanerochaete chrysosporium

Carbohydrate structures are modified and degraded in the biosphere by a myriad of mostly hydrolytic enzymes. Recently, lytic polysaccharide mono-oxygenases (LPMOs) were discovered as a new class of enzymes for cleavage of recalcitrant polysaccharides that instead employ an oxidative mechanism. LPMOs employ copper as the catalytic metal and are dependent on oxygen and reducing agents for activity. LPMOs are found in many fungi and bacteria, but to date no basidiomycete LPMO has been structurally characterized. Here we present the three-dimensional crystal structure of the basidiomycete Phanerochaete chrysosporium GH61D LPMO, and, for the first time, measure the product distribution of LPMO action on a lignocellulosic substrate. The structure reveals a copper-bound active site common to LPMOs, a collection of aromatic and polar residues near the binding surface that may be responsible for regio-selectivity, and substantial differences in loop structures near the binding face compared with other LPMO structures. The activity assays indicate that this LPMO primarily produces aldonic acids. Last, molecular simulations reveal conformational changes, including the binding of several regions to the cellulose surface, leading to alignment of three tyrosine residues on the binding face of the enzyme with individual cellulose chains, similar to what has been observed for family 1 carbohydrate-binding modules. A calculated potential energy surface for surface translation indicates that P. chrysosporium GH61D exhibits energy wells whose spacing seems adapted to the spacing of cellobiose units along a cellulose chain.