Unraveling variations of crystalline cellulose induced by ionic liquid and their effects on enzymatic hydrolysis

The Effect of Cellulose Nanocrystals on the Molecular Organization, Thermomechanical, and Shape Memory Properties of Gelatin-Matrix Composite Films

Gelatin is a natural hydrocolloid with excellent film-forming properties, high processability, and tremendous potential in the field of edible coatings and food packaging. However, its reinforcing by materials such as cellulose nanocrystals (CNC) is often necessary to improve its mechanical behavior, including shape memory properties. Since the interaction between these polymers is complex and its mechanism still remains unclear, this work aimed to study the effect of low concentrations of CNC (2, 6, and 10 weight%) on the molecular organization, thermomechanical, and shape memory properties in mammalian gelatin-based composite films at low moisture content (~10 weight% dry base). The results showed that the presence of CNCs (with type I and type II crystals) interfered with the formation of the gelatin triple helix, with a decrease from 21.7% crystallinity to 12% in samples with 10% CNC but increasing the overall crystallinity (from 21.7% to 22.6% in samples with 10% CNC), which produced a decrease in the water monolayer in the composites. These changes in crystallinity also impacted significantly their mechanical properties, with higher E' values (from 1 × 104 to 1.3 × 104 Pa at 20 °C) and improved thermal stability at higher CNC content. Additionally, the evaluation of their shape memory properties indicated that while molecular interactions between the two components occur, CNCs negatively impacted the magnitude and kinetics of the shape recovery of the composites (more particularly at 10 weight% CNC, reducing shape recovery from 90% to 70%) by reducing the netting point associated with the lower crystallinity of the gelatin. We believe that our results contribute in elucidating the interactions of gelatin-CNC composites at various structural levels and highlights that even though CNC acts as a reinforcement material on gelatin matrices, their interaction are complex and do not imply synergism in their properties. Further investigation is, however, needed to understand CNC-gelatin interfacial interactions with the aim of modulating their interactions depending on their desired application.

Biovalorization of mango byproduct through enzymatic extraction of dietary fiber

Mango is considered one of the most important tropical fruits worldwide in terms of its consumption and consumer acceptability. Its processing generates huge quantities of mango byproducts, which is often discarded unscrupulously into the environment and, therefore, needs effective waste management practices. The extraction of mango peels' dietary fiber using enzymatic method can be a useful valorization strategy for management of mango by-products. In the present investigation, dietary fiber (soluble and insoluble fraction) was extracted by enzymatic hydrolysis using α-amylase, protease, and amyloglucosidase. Highest yield of dietary fiber (67.5%, w/w) was obtained at 60 °C temperature using recommended enzyme concentrations including α-amylase (40 µL), protease (110 µL), and amyloglucosidase (200 µL) after a treatment time of 60 min. SEM analysis indicated the increased porosity of dietary fiber samples caused due to the hydrolytic effect of enzymes on its surface structure, whereas FTIR analysis confirmed the functional groups present in dietary fiber. The coexistence of crystalline and amorphous nature of polymers present in soluble and insoluble fractions of dietary fiber was assessed by XRD analysis. Further, the analysis of functional properties including WHC, OHC, and SC revealed the suitability of using extracted mango peel's dietary fiber in the food systems.

Statistical optimization of bioprocess parameters for enhanced production of bacterial cellulose from K. saccharivorans BC-G1

Bacterial Cellulose (BC) offers a wide range of applications across various industries, including food, biomedical, and textiles, owing to its distinctive properties. Its unique 3D reticulated network of cellulose nanofibers, imparts excellent mechanical qualities, a high water-holding capacity, and thermal stability. Additionally, it possesses remarkable biocompatibility, biodegradability, high crystallinity, and purity. These attributes have offered significant interest in BC within both academic and industrial sectors. However, BC production is associated with high costs due to the use of expensive growth media and low yields. The study reports the potential of our indigenous isolate, Komagataeibacter saccharivorans BC-G1, as BC producer. Statistical optimization of BC production was carried out using Placket-Burman design and Central composite design, by selecting different parameters. Eight significant factors such as temperature, pH, glucose, yeast, peptone, acetic acid, incubation time and % inoculum were studies using ANOVA-based response surface methodology. Results showed that BC yield (8.5 g/L) with 1.8-fold after optimization of parameters. Maximum cellulose production (8.5 ± 1.8 g/L) was obtained using 2% glucose, 0.3% yeast extract, 0.3% peptone, 0.75% (v/v) acetic acid at pH 7.0 for 10 days of incubation with 4% inoculum at 25 °C under static culture. Main effect graph showed incubation time and acetic acid concentration as the most significant parameters affecting BC production in our study. The physicochemical characterization of produced BC was done using FTIR, XRD and SEM techniques.

Nanocellulose-based hydrogels as versatile materials with interesting functional properties for tissue engineering applications

Tissue engineering has emerged as a remarkable field aiming to restore or replace damaged tissues through the use of biomimetic constructs. Among the diverse materials investigated for this purpose, nanocellulose-based hydrogels have garnered attention due to their intriguing biocompatibility, tunable mechanical properties, and sustainability. Over the past few years, numerous research works have been published focusing on the successful use of nanocellulose-based hydrogels as artificial extracellular matrices for regenerating various types of tissues. The review emphasizes the importance of tissue engineering, highlighting hydrogels as biomimetic scaffolds, and specifically focuses on the role of nanocellulose in composites that mimic the structures, properties, and functions of the native extracellular matrix for regenerating damaged tissues. It also summarizes the types of nanocellulose, as well as their structural, mechanical, and biological properties, and their contributions to enhancing the properties and characteristics of functional hydrogels for tissue engineering of skin, bone, cartilage, heart, nerves and blood vessels. Additionally, recent advancements in the application of nanocellulose-based hydrogels for tissue engineering have been evaluated and documented. The review also addresses the challenges encountered in their fabrication while exploring the potential future prospects of these hydrogel matrices for biomedical applications.

Unraveling interplay between lignocellulosic structures caused by chemical pretreatments in enhancing enzymatic hydrolysis

To investigate the interplay between substrate structure and enzymatic hydrolysis (EH) efficiency, poplar was pretreated with acidic sodium-chlorite (ASC), 3 % sodium-hydroxide (3-SH), and 3 % sulfuric acid (3-SA), resulting in different glucose yields of 94.10 %, 74.35 %, and 24.51 %, respectively, of pretreated residues. Residues were fractionated into cellulose, lignin and unhydrolyzed residue after EH (for lignin-carbohydrate complex (LCC) analysis) and analyzed using HPLC, FTIR, XPS, CP MAS 13C NMR and 2D-NMR (Lignin and LCC analysis). After delignification, holocellulose exhibited a dramatic increase in glucose yield (74.35 % to 90.82 % for 3-SH and 24.51 % to 80.0 % for 3-SA). Structural analysis of holocellulose suggested the synergistic interplay among cellulose allomorphs to limit glucose yield. Residual lignin analysis from un/pretreated residues indicated that higher β-β' contents and S/G ratios were favorable to the inhibitory effect but unfavourable to the holocellulose digestibility and followed the trend in the following order: 3-SA (L3) > 3-SH (L2) > native-lignin (L1). Analysis of enzymatically unhydrolyzed pretreated residues revealed the presence of benzyl ether (BE1,2) LCC and phenyl glycoside (PG) bond linking to xylose (X) and mannose (M), which yielded a xylan-lignin-glucomannan network. The stability, steric hindrance and hydrophobicity of this network may play a central role in defining poplar recalcitrance.

Unrevealing the influence of reagent properties on disruption and digestibility of lignocellulosic biomass during alkaline pretreatment

Beyond the conventional consideration of pretreatment severity (PS) responsible for biomass disruption, the influence of reagent properties on biomass (LCB) disruption is often overlooked. To investigate the LCB disruption as a function of reagent properties, reagents with distinct cations (NaOH and KOH) and significantly higher delignification potential were chosen. NaOH solution (3 % w/v) with a measured pH of 13.05 ± 0.01 is considered the reference, against which a KOH solution (pH = 13.05 ± 0.01) was prepared for LCB pretreatment under the same PS. Despite comparable lignin content, varying glucose yield of NaOH (68.76 %) and KOH (46.88 %) pretreated residues indicated the presence of heterogeneously disrupted substrate. Holocellulose extracted from raw poplar (ASC, control) and alkaline pretreated residues (C-NaOH and C-KOH) were analyzed using HPLC, XRD, SEM, TGA/DTG, XPS, and 13CP MAS NMR to investigate the pretreatment-induced structural modification. Results revealed that, despite the same pretreatment severity, better disruption in C-NaOH (higher accessible fibril surface and less-ordered region) leading to higher digestibility than C-KOH, likely due to the smaller ionic radius of Na+, facilitates better penetration into dense LCB matrix. This study elucidates the importance of considering the reagent properties during LCB pretreatment, eventually enhancing consciousness while selecting reagents for efficient LCB utilization.

Modification of Bulk Density, Flow Property and Crystallinity of Microcrystalline Cellulose Prepared from Waste Cotton

The most affordable type of tablet is the immediately compressible tablet, which uses microcrystalline cellulose (MCC), a popular pharmaceutical excipient, as a filler or binder. To make it compatible with different active drugs and excipients, we tried to change some physical properties of the MCC. In the current study, we used a chelating agent to pretreat the waste cotton before pulping, bleaching, and finally, hydrochloric acid degradation with a concentration of 2N at 100 °C temperature for 20 min to prepare MCC. The prepared MCC was treated with different concentrations of sodium hydroxide at room temperature or at -20 °C followed by precipitation with hydrochloric acid or ethanol with complete washing with distilled water till neutralization. Evaluation of the degree of polymerization (DP) and FT-IR spectrum confirm the identity of the microcrystalline cellulose. The DP was found to be 216. The bulk density of the unmodified MCC was 0.21 while that of modified MCC varied from 0.253 to 0.594. The modified MCC powder showed good flow properties compared to the unmodified MCC as evaluated by the Hausner index, Carr's index and the angle of repose. The scanning electron microscopy (SEM) of the MCC revealed that the rod shape has been changed to an oval shape due to treatment with sodium hydroxide at -20 °C. The X-ray crystallographic (XRD) analysis indicated that the unmodified MCC and standard MCC showed the crystallinity index (CrI) value of 86.82% and 87.63%, respectively, while the value ranges from 80.18% to 60.7% among the modified MCC powder. The differences in properties of the MCC might be due to the variation of rearrangement of the cellulose chain among the MCC particles due to treatment with different concentrations of a base at different temperatures and precipitation environments. This has enabled us to prepare MCC with different properties which might be compatible with different drugs.

Strong, Shape-Memory Lignocellulosic Aerogel via Wood Cell Wall Nanoscale Reassembly

Polymer shape-memory aerogels (PSMAs) are prospects in various fields of application ranging from aerospace to biomedicine, as advanced thermal insulators, actuators, or sensors. However, the fabrication of PSMAs with good mechanical performance is challenging and is currently dominated by fossil-based polymers. In this work, strong, shape-memory bio-aerogels with high specific surface areas (up to 220 m²/g) and low radial thermal conductivity (0.042 W/mK) were prepared through a one-step treatment of native wood using an ionic liquid mixture of [MTBD]⁺[MMP]^-/DMSO. The aerogel showed similar chemical composition similar to native wood. Nanoscale spatial rearrangement of wood biopolymers in the cell wall and lumen was achieved, resulting in flexible hydrogels, offering design freedom for subsequent aerogels with intricate geometries. Shape-memory function under stimuli of water was reported. The chemical composition and distribution, morphology, and mechanical performance of the aerogel were carefully studied using confocal Raman spectroscopy, AFM, SAXS/WAXS, NMR, digital image correlation, etc. With its simplicity, sustainability, and the broad range of applicability, the methodology developed for nanoscale reassembly of wood is an advancement for the design of biobased shape-memory aerogels.

Impact of pulping routes of rice straw on cellulose nanoarchitectonics and their behavior toward Indigo dye

This work deals with emphasizing the relation between particle dimension distribution of nanocellulose (PDD) particles with its efficiency as stabilizing/adsorbent agent of Indigo dye. In this respect, different pulping reagents were used in preparation of Rice straw pulps as precursors for nanocelluloses using acid hydrolysis and oxidizing agents [(KMnO4 and NH4)2S2O8] methods. The PDD was estimated by indirect method through processing the TEM images using the software ImageJ. The resulting nanocelluloses were also characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectra (FTIR) together with sulfate ester and carboxyl contents. The data showed the effective role of pulping reagent on PDD. The cellulose nanocrystals (CNCs) from NaOH-AQ pulp, with the longest crystal length (204.4 ± 107.8 nm) and the lowest diameter (6.7 ± 2.3 nm), exhibited most stabilized suspension of dye; however, the highest adsorption capacity was accompanied the oxidized nanocellulose (Ox-NC) from neutral RS pulp with lowest PDD (4.98 ± 1.6 and 90.5 ± 3.14), together with highest COO content (476.46 μmol/g).

Use of Fourier Series in X-ray Diffraction (XRD) Analysis and Fourier-Transform Infrared Spectroscopy (FTIR) for Estimation of Crystallinity in Cellulose from Different Sources

Cellulose crystallinity can be described according to the crystal size and the crystallinity index (CI). In this research, using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods, we studied the crystallinity of three different types of cellulose: banana rachis (BR), commercial cellulose (CS), and bacterial cellulose (BC). For each type of cellulose, we analyzed three different crystallization grades. These variations were obtained using three milling conditions: 6.5 h, 10 min, and unmilled (films). We developed a code in MATLAB software to perform deconvolution of the XRD data to estimate CI and full width at half-maximum (FWHM). For deconvolution, crystalline peaks were represented with Voigt functions, and a Fourier series fitted to the amorphous profile was used as the amorphous contribution, which allowed the contribution of the amorphous profile to be more effectively modeled. Comparisons based on the FTIR spectra and XRD results showed there were no compositional differences between the amorphous samples. However, changes associated with crystallinity were observed when the milling time was 10 min. The obtained CI (%) values show agreement with values reported in the literature and confirm the effectiveness of the method used in this work in predicting the crystallization aspects of cellulose samples.

One-step lignocellulose fractionation using acid/pentanol pretreatment for enhanced fermentable sugar and reactive lignin production with efficient pentanol retrievability

To valorize whole lignocellulosic biomass, this study proposed a biphasic solvent system using dilute acid (DA)/pentanol pretreatment. Effects of the key factors, i.e., temperature and pentanol concentration, on aspen were evaluated. Under identified optimal pretreatment conditions (160 °C, 60% pentanol), 85% and 91% of lignin and hemicellulose were solubilized in separate organic and liquid phases, respectively, while 91.1% of cellulose was retained in solid fraction. Enzymatic digestibility efficiency of pretreated cellulose was ∼ 6.4-times higher than that of untreated biomass. Notably, excellent pentanol recovery rates were obtained after four-times recycling (84%) with great cellulose digestibility (81%) and delignification (71%) performance. The recovered lignin contained low levels of contaminated sugars (<1%), while it could stabilize and protect high amounts of β-O-4 bonds. Besides, high phenolic OH content was found in lignin, which could be utilized for lignin-based biomaterials. Therefore, DA/pentanol pretreatment is an innovative promising technology for lignocellulosic valorization towards biorefinery.

Computational vaccinology guided design of multi-epitope subunit vaccine against a neglected arbovirus of the Americas

Mayaro virus (MAYV) is an arbovirus found in the Americas that can cause debilitating arthritogenic disease. Although it is an emerging virus, the only current approach is vector control, as there are no approved vaccines to prevent MAYV infection nor therapeutics to treat it. In search of an effective vaccine candidate against MAYV, we used immunoinformatics and molecular modeling to attempt to identify promiscuous T-cell epitopes of the nonstructural polyproteins (nsP1, nsP2, nsP3, and nsP4) from 127 MAYV genomes sequenced in the Americas (08 Bolivia, 72 Brazil, 04 French Guiana, 05 Haiti, 20 Peru, 04 Trinidad and Tobago, and 14 Venezuela). For this purpose, consensus sequences of 360 proteins were used to identify short protein sequences that can bind to MHC I class (MHC II). Our analysis revealed 56 potential MHC-I/TCD8+ (29 MHC-II/TCD4+) epitopes, but only 6 (16) TCD8+ (TCD4+) epitopes showed high antigenicity and conservation, non-allergenicity, non-toxicity, and excellent population coverage. Finally, classical and quantum mechanical calculations (QM:MM) were used to improve the quality of the docking calculations, with the QM part of the simulations performed using the density functional theory formalism (DFT). These results provide insights for the advancement of diagnostic platforms, vaccine development, and immunotherapeutic interventions.Communicated by Ramaswamy H. Sarma.

Chemical Characteristics of Wood Cell Wall with an Emphasis on Ultrastructure: A Mini-Review

Wood is complex in its chemical composition that has an important influence on its chemical behavior and mechanical strength. The complexity is reflected in the ultrastructure of the wood cell wall. In particular, the concentration of main components (cellulose, hemicelluloses and lignin) changes depending on many factors such as the different type or parts of wood, and varies in different cell wall layers. From an ultrastructural standpoint, we describe the current level of knowledge about chemical characteristics of the wood cell walls. The information of distribution of main components in the cell walls of normal wood, reaction wood and water-logged archaeological wood, the cellulose microfibrils orientation, and the interactions between main components were presented based on the use of advanced techniques including transmission electron microscopy, scanning electron microscopy, spectral imaging and nuclear magnetic resonance. In addition, the chemical changes of the wood cell wall during pretreatment are discussed. This mini-review not only provides a better understanding of wood chemistry, but also brings new insights into cell wall recalcitrance.

Conversion of Cellulose and Lignin Residues into Transparent UV-Blocking Composite Films

The valorization of cellulose and lignin residues in an integrated biorefinery is of great significance to improve the overall economics but has been challenged by their structural recalcitrance, especially for lignin residue. In this work, a facile chemical conversion route to fabricating functional UV-blocking cellulose/lignin composite films through a facile dissolution-regeneration process using these biomass residues was proposed. Three representative lignin residues, i.e., aspen and poplar wood lignin, and corn stover (CS) lignin were assessed for their feasibility for the film fabrication. The UV-blocking performance of the composite films were comparatively investigated. Results showed that all these three lignin residues could enhance the UV-blocking property of the composite films, corresponding to the reduction in the optical energy band gap from 4.31 to 3.72 eV, while poplar lignin had a considerable content of chromophores and showed the best UV-blocking enhancement among these three assessing lignins. The enhancement of UV-blocking property was achieved without compromising the visible-light transparency, mechanical strength and thermal stability of the composite films even at 4% lignin loading. This work showed the high promise of integrating biomass residue conversion into lignocellulose biorefinery for a multi-production purpose.

Structural Evolution of Cellulose from Bamboo Fibers and Parenchyma Cells during Ionic Liquid Pretreatment for Enhanced Hydrolysis

Bamboo fibers and parenchyma cells, the two dominant types of cells in bamboo, exhibit some interesting differences in cellulose crystalline structures. In the present investigation, we further demonstrated that these structural differences affect their response during ionic liquid (IL) pretreatment and the sugar conversion yield, by tracking their changes in morphology, chemical, and crystalline structures. All of the results pointed to the fact that the cellulose from bamboo fibers exhibited higher recalcitrance to IL pretreatment, with a significantly lower change in crystallinity index, d spacings from the (110) and (11̅0) planes, crystallite sizes, and easier transformation from cellulose I to cellulose II after pretreatment, as compared to that from parenchyma cells. Furthermore, the crystalline parameters of (110) and (11̅0) lattice planes exhibited more changes compared to the (200) direction. This investigation highlights the significance of parenchyma cell wastes from bamboo processing plants as a competitive candidate for the biorefinery industry.

Critical assessment of structure-based approaches to improve protein resistance in aqueous ionic liquids by enzyme-wide saturation mutagenesis

Ionic liquids (IL) and aqueous ionic liquids (aIL) are attractive (co-)solvents for green industrial processes involving biocatalysts, but often reduce enzyme activity. Experimental and computational methods are applied to predict favorable substitution sites and, most often, subsequent site-directed surface charge modifications are introduced to enhance enzyme resistance towards aIL. However, almost no studies evaluate the prediction precision with random mutagenesis or the application of simple data-driven filtering processes. Here, we systematically and rigorously evaluated the performance of 22 previously described structure-based approaches to increase enzyme resistance to aIL based on an experimental complete site-saturation mutagenesis library of Bacillus subtilis Lipase A (BsLipA) screened against four aIL. We show that, surprisingly, most of the approaches yield low gain-in-precision (GiP) values, particularly for predicting relevant positions: 14 approaches perform worse than random mutagenesis. Encouragingly, exploiting experimental information on the thermostability of BsLipA or structural weak spots of BsLipA predicted by rigidity theory yields GiP = 3.03 and 2.39 for relevant variants and GiP = 1.61 and 1.41 for relevant positions. Combining five simple-to-compute physicochemical and evolutionary properties substantially increases the precision of predicting relevant variants and positions, yielding GiP = 3.35 and 1.29. Finally, combining these properties with predictions of structural weak spots identified by rigidity theory additionally improves GiP for relevant variants up to 4-fold to ∼10 and sustains or increases GiP for relevant positions, resulting in a prediction precision of ∼90% compared to ∼9% in random mutagenesis. This combination should be applicable to other enzyme systems for guiding protein engineering approaches towards improved aIL resistance.

Bio-based and bio-inspired adhesives from animals and plants for biomedical applications

With the "many-headed" slime mold Physarum polycelphalum having been voted the unicellular organism of the year 2021 by the German Society of Protozoology, we are reminded that a large part of nature's huge variety of life forms is easily overlooked - both by the general public and researchers alike. Indeed, whereas several animals such as mussels or spiders have already inspired many scientists to create novel materials with glue-like properties, there is much more to discover in the flora and fauna. Here, we provide an overview of naturally occurring slimy substances with adhesive properties and categorize them in terms of the main chemical motifs that convey their stickiness, i.e., carbohydrate-, protein-, and glycoprotein-based biological glues. Furthermore, we highlight selected recent developments in the area of material design and functionalization that aim at making use of such biological compounds for novel applications in medicine - either by conjugating adhesive motifs found in nature to biological or synthetic macromolecules or by synthetically creating (multi-)functional materials, which combine adhesive properties with additional, problem-specific (and sometimes tunable) features.

A new cotton functionalized with iron(III) trimer-like metal framework as an effective strategy for the adsorption of triarylmethane dye: An insight into the dye adsorption processes

A new Cotton@Fe-BTC composite formed by Fe-BTC (BTC-H3: trimesic acid) metal framework (Fe-BTC MOF loading as high 38 wt %) supported by cellulose fiber is synthesized in aqueous media using a simple and green preparation method, described for the first time in this manuscript. This new strategy relies on the synergetic effect of the pure cellulose and MOFs frameworks resulting in hybrid nanofibers of MOFs@cellulose composite. A complete characterization of the composite material reveals its structural similarity to MIL-100(Fe), a Fe-BTC material. The Cotton@Fe-BTC composite potential use as an eco-friendly and low-cost adsorbent was evaluated for its adsorptive performance for the removal of dye belonging to the triarylmethane dye family (Malachite Green (MQ), Brilliant Green (BG), Pararosaniline (PR), Basic Fuchsine (BF), Crystal Violet (CV), Methyl Green (Met-G), Victoria Blue B (VB), Acid Fuchsin (AF) and Aniline Blue (AB)) in aqueous solution. The fast kinetics and high dye removal efficiencies (>90%) obtained in aqueous solutions. The structure of Cotton@Fe-BTC network, contributed to the remarkable adsorption properties towards a variety of triphenylmethanedye. The interparticle studies showed two main steps in the dye adsorption processes, with the exception of AF and BG. The equilibrium adsorption capacities qe (mg/g) follow the order: AF (3.64) Collapse

Key Words

• Adsorption
• Fe-BTC
• Natural cotton
• Solvation/desolvation penalty processes
• Triphenylmetane dye
• Water

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MESH Headings Collapse

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Affiliation(s)

J.E. Conde-González Departamento de Química, Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna, Tenerife, Spain
P. Lorenzo-Luis Inorganic Chemistry Area, Section of Chemistry Faculty of Science, Tenerife, Spain Instituto Universitario de Bio-Orgánica “Antonio González”, University of La Laguna, Tenerife, Spain
V. Salvadó Department de Química, Facultat de Ciències, Universitat de Girona, C/ M Aurèlia Capmany, 69, 17003 Girona, Spain
J. Havel Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5/A14, 625 00 Brno, Czech Republic
E.M. Peña-Méndez Departamento de Química, Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna, Tenerife, Spain

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Comprehensive investigation of multiples factors in sulfuric acid pretreatment on the enzymatic hydrolysis of waste straw cellulose

The prerequisite for cellulosic biochemical production from lignocellulosic materials is efficient enzymatic hydrolysis that is a complicated heterogeneous catalytic process and affected by the complex lignin-cellulose-hemicellulose network. Understanding the main influencing factors for enzymatic hydrolysis is of substantial significance to guide the design of a biorefinery process. An experimental study of the pretreatment indicated that acid pretreatment is preferable for herbaceous feedstocks. Therefore, the classic dilute sulfuric acid pretreatment was utilized to hydrolyze and remove hemicellulose from three representative types of agricultural straws at various intensities. From the enzymatic hydrolysis of residual cellulose perspective, the crystallinity index and enzyme accessibility of the pretreated materials were also mathematically correlated to hemicellulose removals, respectively. For the better insight and understanding of the mathematical logics, the linear and nonlinear kinetic models were therefore compared, and the relationship was established by the five-parameter logistic equations and Allosteric sigmoidal models with well fittings.

Addition of Various Cellulosic Components to Bacterial Nanocellulose: A Comparison of Surface Qualities and Crystalline Properties

Bacterial nanocellulose (BNC) is a biocompatible material with a lot of potential. To make BNC commercially feasible, improvements in its production and surface qualities must be made. Here, we investigated the in situ fermentation and generation of BNC by addition of different cellulosic substrates such as Avicel and carboxymethylcellulose (CMC) and using Komagataeibacter sp. SFCB22-18. The addition of cellulosic substrates improved BNC production by a maximum of about 5 times and slightly modified its structural properties. The morphological and structural properties of BNC were investigated by using Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy and X-ray diffraction. Furthermore, a type-A cellulose-binding protein derived from Clostridium thermocellum, CtCBD3, was used in a novel biological analytic approach to measure the surface crystallinity of the BNC. Because Avicel and CMC may adhere to microfibrils during BNC synthesis or crystallization, cellulose-binding protein could be a useful tool for identifying the crystalline properties of BNC with high sensitivity.

Regenerated Cellulose Products for Agricultural and Their Potential: A Review

Cellulose is one of the most abundant natural polymers with excellent biocompatibility, non-toxicity, flexibility, and renewable source. Regenerated cellulose (RC) products result from the dissolution-regeneration process risen from solvent and anti-solvent reagents, respectively. The regeneration process changes the cellulose chain conformation from cellulose I to cellulose II, leads the structure to have more amorphous regions with improved crystallinity, and inclines towards extensive modification on the RC products such as hydrogel, aerogel, cryogel, xerogel, fibers, membrane, and thin film. Recently, RC products are accentuated to be used in the agriculture field to develop future sustainable agriculture as alternatives to conventional agriculture systems. However, different solvent types and production techniques have great influences on the end properties of RC products. Besides, the fabrication of RC products from solely RC lacks excellent mechanical characteristics. Thus, the flexibility of RC has allowed it to be homogenously blended with other materials to enhance the final products' properties. This review will summarize the properties and preparation of potential RC-based products that reflect its application to replace soil the plantation medium, govern the release of the fertilizer, provide protection on crops and act as biosensors.

An aptamer highly specific to cellulose enables the analysis of the association of cellulose with matrix cell wall polymers in vitro and in muro

The current toolbox of cell wall-directed molecular probes has been pivotal for advancing basic and application-oriented plant carbohydrate research; however, it still exhibits limitations regarding target diversity and specificity. Scarcity of probes targeting intramolecular associations between cell wall polymers particularly hinders our understanding of the cell wall microstructure and affects the development of effective means for its efficient deconstruction for bioconversion. Here we report a detailed characterization of a cellulose-binding DNA aptamer CELAPT MINI using a combination of various in vitro biochemical, biophysical, and molecular biology techniques. Our results show evidence for its high specificity towards long non-substituted β-(1-4)-glucan chains in both crystalline and amorphous forms. Fluorescent conjugates of CELAPT MINI are applicable as in situ cellulose probes and are well suited for various microscopy techniques, including super-resolution imaging. Compatibility of fluorescent CELAPT MINI variants with immunodetection of cell wall matrix polymers enabled them simultaneously to resolve the fibrillar organization of complex cellulose-enriched pulp material and to quantify the level of cellulose masking by xyloglucan and xylan. Using enzymatically, chemically, or genetically modulated Brachypodium internode sections we showed the diversity in cell wall packing among various cell types and even cell wall microdomains. We showed that xylan is the most prominent, but not the only, cellulose-masking agent in Brachypodium internode tissues. These results collectively highlight the hitherto unexplored potential to expand the cell wall probing toolbox with highly specific and versatile in vitro generated polynucleotide probes.

Natural surfactant-aided dilute sulfuric acid pretreatment of waste wheat straw to enhance enzymatic hydrolysis efficiency

Traditional surfactants have been reported to enhance enzymatic saccharification of lignocellulose, however, it is important to transfer these findings to a system that uses a high-efficiency and low-toxicity natural surfactant instead. In this work, a novel hybrid method involving use of the natural surfactant (humic acid, HA) during mild acid (H₂SO₄) pretreatment was developed for waste wheat straw (WWS) biorefinery. The HA was found to help remove lignin up to 40.6%, and hemicellulose up to 96.2%. As a result of these changes, the enzymatic hydrolysis efficiency reached as high as 92.9%. The success of enzymatic digestion was partly attributed to the improved accessibility of cellulose to cellulase and changes in lignocellulose structures. We anticipate that these findings will be used to further evaluate HA as a beneficial surfactant in biorefinery pretreatment processes, and perhaps spur others to identify other natural surfactants that may prove even more effective.

Understanding the promoting effect of non-catalytic protein on enzymatic hydrolysis efficiency of lignocelluloses

Lignin deposits formed on the surface of pretreated lignocellulosic substrates during acidic pretreatments can non-productively adsorb costly enzymes and thereby influence the enzymatic hydrolysis efficiency of cellulose. In this article, peanut protein (PP), a biocompatible non-catalytic protein, was separated from defatted peanut flour (DPF) as a lignin blocking additive to overcome this adverse effect. With the addition of 2.5 g/L PP in enzymatic hydrolysis medium, the glucose yield of the bamboo substrate pretreated by phenylsulfonic acid (PSA) significantly increased from 38 to 94% at a low cellulase loading of 5 FPU/g glucan while achieving a similar glucose yield required a cellulase loading of 17.5 FPU/g glucan without PP addition. Similar promotion effects were also observed on the n-pentanol-pretreated bamboo and PSA-pretreated eucalyptus substrates. The promoting effect of PP on enzymatic hydrolysis was ascribed to blocking lignin deposits via hydrophobic and/or hydrogen-bonding interactions, which significantly reduced the non-productive adsorption of cellulase onto PSA lignin. Meanwhile, PP extraction also facilitated the utilization of residual DPF as the adhesive for producing plywood as compared to that without protein pre-extraction. This scheme provides a sustainable and viable way to improve the value of woody and agriculture biomass. Peanut protein, a biocompatible non-catalytic protein, can block lignin, improve enzymatic hydrolysis efficiency and thereby facilitate the economics of biorefinery.

Generation of highly amenable cellulose-Iβ via selective delignification of rice straw using a reusable cyclic ether-assisted deep eutectic solvent system

Cellulolytic enzymes can readily access the cellulosic component of lignocellulosic biomass after the removal of lignin during biomass pretreatment. The enzymatic hydrolysis of cellulose is necessary for generating monomeric sugars, which are then fermented into ethanol. In our study, a combination of a deep eutectic (DE) mixture (of 2-aminoethanol and tetra-n-butyl ammonium bromide) and a cyclic ether (tetrahydrofuran) was used for selective delignification of rice straw (RS) under mild conditions (100 °C). Pretreatment with DE-THF solvent system caused ~ 46% delignification whereas cellulose (~ 91%) and hemicellulose (~ 67%) recoveries remained higher. The new solvent system could be reused upto 10 subsequent cycles with the same effectivity. Interestingly, the DE-THF pretreated cellulose showed remarkable enzymatic hydrolysability, despite an increase in its crystallinity to 72.3%. Contrary to conventional pretreatments, we report for the first time that the enzymatic hydrolysis of pretreated cellulose is enhanced by the removal of lignin during DE-THF pretreatment, notwithstanding an increase in its crystallinity. The current study paves way for the development of newer strategies for biomass depolymerization with DES based solvents.

Minimizing Organic Waste Generated by Pineapple Crown: A Simple Process to Obtain Cellulose for the Preparation of Recyclable Containers

In this study, cellulose was obtained from the residues of pineapple crown by means of simple acid pretreatment and subsequent alkaline treatment. The pretreatment consisted of washing, drying, and chopping with high shear at pH = 5 under heating. The content of cellulose, hemicellulose, and lignin in the pineapple crown was determined by chemical methods. The cellulose obtained was compared with commercial cellulose by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis, and X-ray diffraction (XDR). Thus, from the obtained fiber cellulose, a food container was prepared, and its physical-mechanical properties were determined. Then, after alkali treatment, the purity of cellulose was 84.7% from the pineapple crown (56.0%) and was compared with commercial cellulose (95%). FTIR results confirmed the removal of the non-cellulosic compounds after alkali treatment. The maximum pyrolysis temperature increased to 356 °C, higher than the original fiber (322 °C), indicating greater thermal stability after chemical treatment. Furthermore, the crystallinity increased to 68% with respect to the original fiber (27%). The physical properties of the container showed a decrease in the parameters in wet 95% RH, as expected, thus facilitating its reuse. These results indicate that the pineapple crown cellulose can be obtained with significant purity, from a single chemical treatment. In addition, this polymorphous cellulose can be used to make ecofriendly reusable food containers.

Green Synthesis of Free Standing Cellulose/Graphene Oxide/Polyaniline Aerogel Electrode for High-Performance Flexible All-Solid-State Supercapacitors

The cellulose/graphene oxide (GO) networks as the scaffold of free-standing aerogel electrodes are developed by using lithium bromide aqueous solution, as the solvent, to ensure the complete dissolution of cotton linter pulp and well dispersion/reduction of GO nanosheets. Polyaniline (PANI) nanoclusters are then coated onto cellulose/GO networks via in-situ polymerization of aniline monomers. By optimized weight ratio of GO and PANI, the ternary cellulose/GO3.5/PANI aerogel film exhibits well-defined three-dimensional porous structures and high conductivity of 1.15 S/cm, which contributes to its high areal specific capacitance of 1218 mF/cm2 at the current density of 1.0 mA/cm2. Utilizing this cellulose/GO3.5/PANI aerogel film as electrodes in a symmetric configuration supercapacitor can result in an outstanding energy density as high as 258.2 µWh/cm2 at a power density of 1201.4 µW/cm2. Moreover, the device can maintain nearly constant capacitance under different bending deformations, suggesting its promising applications in flexible electronics.

Exploring the flexibility of cellulase cocktail obtained from mutant UV-8 of Talaromyces verruculosus IIPC 324 in depolymerising multiple agro-industrial lignocellulosic feedstocks

Effective management and the valorization of agro-industrial lignocellulosic feedstocks can only be realized if a versatile cellulase cocktail is developed that can release glucose at affordable cost irrespective of biomass type. In the present study the flexibility of using cellulase cocktail obtained from mutant UV-8 of Talaromyces verruculosus IIPC 324 in depolymerizing multiple agro-industrial lignocellulosic feedstocks was explored. Five different dilute acid pretreated biomasses were evaluated and cellulase loading was done at 25 mg protein/g cellulose content. After 72 h of hydrolysis at 55 °C and pH 4.5, corn cob and rice straw emerged as the easiest and toughest substrates with saccharification yield of 83.9 ± 1.17 and 35.5 ± 1.16% respectively from their cellulose fraction. Addition of PEG 6000 could retain >65% of all mono-component enzymes present in cellulase cocktail. Structural elucidation of biomasses gave an insight about key features responsible for variable recalcitrance in the different agro-industrial feedstock. Cellulose hydrolysis showed a significant negative correlation in the order of Cr I > S/G ratio > ash content. The chemical composition of lignin had a major impact on enzyme-lignin interactions. Higher H lignin content and lower S/G ratio promoted enzyme desorption, thereby increasing the likelihood of their recycling and reuse.

Partially Acetylated Cellulose Dissolved in Aqueous Solution: Physical Properties and Enzymatic Hydrolysis

Cellulose acetate is one of the most important cellulose derivatives. The use of ionic liquids in cellulose processing was recently found to act both as a solvent and also as a reagent. A recent study showed that cellulose dissolution in the ionic liquid 1-ethyl-3-methylimidazoliumacetate (EMIMAc) mixed with dichloromethane (DCM) resulted in controlled homogenous cellulose acetylation; yielding water-soluble cellulose acetate (WSCA). This research investigated the properties of cellulose acetate prepared in this manner, in an aqueous solution. The results revealed that WSCA fully dissolves in water, with no significant sign of molecular aggregation. Its conformation in aqueous solution exhibited a very large persistence length, estimated as over 10 nm. The WSCA exhibited surface activity, significantly reducing the surface tension of water. Because of the molecular dissolution of WSCA in water, augmented by its amphiphilicity, aqueous solutions of WSCA exhibited an overwhelmingly high rate of enzymatic hydrolysis.

Mechanical properties of cellulose aerogels and cryogels

Highly porous and lightweight cellulose materials were prepared via dissolution-coagulation and different drying routes. Cellulose of three different molecular weights was dissolved in an ionic liquid/dimethyl sulfoxide mixture. Drying was performed either with supercritical CO2 resulting in "aerogels", or via freeze-drying resulting in "cryogels". The influence of cellulose molecular weight, concentration and drying method on the morphology, density, porosity and specific surface area was determined. The mechanical properties of cellulose cryogels and aerogels under uniaxial compression were studied in detail and analyzed in the view of existing models developed for porous materials. It was demonstrated that the Poisson's ratio of cellulose aerogels is not equal to zero, contrary to what is usually reported in the literature, but decreases with an increase in density. Compressive modulus and yield stress of cryogels turned out to be higher than those of aerogels taken at the same density. This was interpreted by the different morphology of the porous materials studied.

Preparation of Reswellable Amorphous Porous Celluloses through Hydrogelation from Ionic Liquid Solutions

In this study, we have performed the preparation of reswellable amorphous porous celluloses through regeneration from hydrogels. The cellulose hydrogels were first prepared from solutions with an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), in different concentrations. Lyophilization of the hydrogels efficiently produced the regenerated celluloses. The powder X-ray diffraction and scanning electron microscopic measurements of the products suggest an amorphous structure and porous morphology, respectively. Furthermore, the pore sizes of the regenerated celluloses, or in turn, the network sizes of cellulose chains in the hydrogels, were dependent on the concentrations of the initially prepared solutions with BMIMCl, which also affected the tensile mechanical properties. It was suggested that the dissolution states of the cellulose chains in the solutions were different, in accordance with the concentrations, which representatively dominated the pore and network sizes of the above materials. When the porous celluloses were immersed in water, reswelling was observed to regenerate the hydrogels.

Evaluation and characterization of novel sources of sustainable lignocellulosic residues for bioethanol production using ultrasound-assisted alkaline pre-treatment

In recent years, research is focused on finding a sustainable and eco-friendly lignocellulosic biomass for the effective production of bioethanol to meet the world's energy demand. The present study investigates the bioethanol production potential of four different lignocellulosic biomass residues viz., Saccharum arundinaceum (hardy sugar cane), Arundo donax (giant reed), Typha angustifolia (narrow-leaved cattail), and Ipomoea carnea (pink morning glory). The maximum reducing sugar release showed 185.00 ± 1.57, 213.73 ± 3.47, 187.57 ± 2.14, 294.08 ± 3.98 mg/g and fermentation efficiency of 72.60 ± 8.17%, 82.59 ± 7.42%, 77.45 ± 7.35%, and 85.04 ± 8.37% which was analyzed by estimating the percentage of bioethanol yield were achieved for Saccharum arundinaceum, Arundo donax, Typha angustifolia, and Ipomoea carnea, respectively. The chemical composition of biomass was characterized using National Renewable Energy Limited (NREL) protocol. The effect of ultrasound (US)-assisted alkaline pre-treatment on the four biomasses was characterized by different techniques. The cavitation phenomena of US-assisted alkaline pre-treatment was evident from the decreased value of lignin percentage, increased surface porosity and area, changes in crystallinity index (CrI) values and in the functional groups of biomass. The results revealed that all the four lignocellulosic biomass residues could be utilized as an effective and sustainable source for the production of bioethanol using US-assisted sodium hydroxide as a pre-treatment tool.

Development of co-immobilized tri-enzyme biocatalytic system for one-pot pretreatment of four different perennial lignocellulosic biomass and evaluation of their bioethanol production potential

Today, many researchers are focusing on research for alternative promising energy sources and sustainable technology for bioethanol production to meet the increasing global energy demand. Here, we develop a novel one-pot pretreatment technology by co-immobilizing laccase, cellulase and β-glucosidase to act as a tri-enzyme biocatalyst for evaluating the bioethanol production potential of four sustainable lignocellulosic biomasses viz., Typha angustifolia, Arundo donax, Saccharum arundinaceum, and Ipomoea carnea. The co-immobilized enzyme system was more stable at different temperatures and at longer storage, compared to free enzyme. During enzymatic saccharification, Saccharum arundinaceum showed higher total reducing sugar of 205 ± 3.73 mg/g when compared to other biomass. The highest percentage of bioethanol yield of 63.43 ± 9.35% was obtained with Ipomoea carnea. The effects of co-immobilized tri-enzyme biocatalyst on the biomasses were evaluated. The results revealed that the co-immobilized tri-enzyme biocatalyst could act as effective one-pot pretreatment for the production of bioethanol from lignocellulosic biomass.

Facile Tuning of the Surface Energy of Cellulose Nanofibers for Nanocomposite Reinforcement

The isolation of nanocellulose from lignocellulosic biomass, with desirable surface chemistry and morphology, has gained extensive scientific attention for various applications including polymer nanocomposite reinforcement. Additionally, environmental and economic concerns have driven researchers to explore viable alternatives to current isolation approaches, employing chemicals with reduced environmental impact. To address these issues, in this study, we have tuned the amphiphilic behavior of cellulose nanofibers (CNFs) by employing controlled alkali treatment, instead of in combination with expensive, environmentally unsustainable conventional approaches. Microscopic and spectroscopic analysis demonstrated that this approach is capable of tuning composition and interfacial tension of CNFs through a careful control of the quantity of residual lignin and hemicellulose. To elucidate the performance of CNF as an efficient reinforcing nanofiller in hydrophobic polymer matrices, prevulcanized natural rubber (NR) latex was employed as a suitable host polymer. CNF/NR nanocomposites with different CNF loading levels (0.1-1 wt % CNF) were prepared by a casting method. It was found that the incorporation of 0.1 wt % CNF treated with a 0.5 w/v % sodium hydroxide solution led to the highest latex reinforcement efficiency, with an enhancement in tensile stress and toughness of 16% to 42 MPa and 9% to 197 MJ m^-3, respectively. This property profile offers a potential application for the high-performance medical devices such as condoms and gloves.

Thermogravimetric analysis and kinetic modeling of low-transition-temperature mixtures pretreated oil palm empty fruit bunch for possible maximum yield of pyrolysis oil

The impacts of low-transition-temperature mixtures (LTTMs) pretreatment on thermal decomposition and kinetics of empty fruit bunch (EFB) were investigated by thermogravimetric analysis. EFB was pretreated with the LTTMs under different duration of pretreatment which enabled various degrees of alteration to their structure. The TG-DTG curves showed that LTTMs pretreatment on EFB shifted the temperature and rate of decomposition to higher values. The EFB pretreated with sucrose and choline chloride-based LTTMs had attained the highest mass loss of volatile matter (78.69% and 75.71%) after 18 h of pretreatment. For monosodium glutamate-based LTTMs, the 24 h pretreated EFB had achieved the maximum mass loss (76.1%). Based on the Coats-Redfern integral method, the LTTMs pretreatment led to an increase in activation energy of the thermal decomposition of EFB from 80.00 to 82.82-94.80 kJ/mol. The activation energy was mainly affected by the demineralization and alteration in cellulose crystallinity after LTTMs pretreatment.

Hydrothermal alkaline sulfite pretreatment in the delivery of fermentable sugars from sugarcane bagasse

Integration of hydrothermal and alkaline processing in the formation of upgradable sugars for advanced processing of sugarcane bagasse residues.