Hydrolysis Of Cellulose Research Articles

Sustainable production of sophorolipid biosurfactants using renewable cellulose‐derived feedstocks

AbstractGlycolipids produced and secreted by oleaginous yeasts are renewable compounds with important physico‐chemical properties, and multiple biological and industrial applications. The large‐scale production of these compounds has been limited by high production costs and low yields. The sophorolipid‐producing yeast Pseudohyphozyma bogoriensis may possess the ability to grow in fermentation systems using carbon substrates deriving from inexpensive lignocellulosic biomass, while simultaneously secreting high value biomaterials. In this study, comparative analyses between different cellulose‐derived carbon sources including glucose, cellobiose, and sodium carboxymethyl cellulose confirmed the ability of P. bogoriensis to grow and accumulate glycolipids using these substrates. On a dry weight basis, the highest yields of about 4% (wt/wt) glycolipids were obtained when cellobiose was supplemented at 10 g/L in shake‐flask fermentations. When the unconventional carbon substrate sodium carboxymethyl cellulose was supplemented, cultures exhibited a lower glycolipid yield of 0.3% (wt/wt), but the dry weight was higher compared to other substrates. Analytical analyses using various chromatography methods confirmed the chemical profiles, whereas both monoacetylated and diacetylated sophorolipid forms with 22 carbon long‐chain hydroxy fatty acid were identified in all glycolipid extracts. Surface tension (ST) and critical micelle concentration (CMC) measurements showed that glycolipids produced on cellulose‐derived substrates exhibited similar or even superior physical properties compared with glucose. Furthermore, availability of the yeast genome sequences facilitated the identification of putative genes that may be involved in cellulose hydrolysis (e.g., cellulase‐like). Information on genomic and metabolic pathways is a prerequisite for trait improvement toward increasing the production of high value biomaterials.

Efficient hydrolysis of cellulose into sugars in aqueous systems using fibrous core-shell structure FS@C/HPW

Phosphotungstic acid hydrate (HPW)-doped hydroxyl-rich hydrothermal carbon-coated fibrous silica catalyst (FS@C/HPW) is fabricated to induce the highly efficient hydrolysis of cellulose to sugar in an ultra-low acid aqueous system. The obtained FS90@C/HPW12 owns good thermal stability under 200 °C and the highest specific surface area at 28 m2/g. Owing to its special fibrous microstructures, FS90@C/HPW12 can cause linear damage and structural fragmentation on the surface of cellulose during hydrolysis. Accordingly, rather highly efficient hydrolysis with the cellulose conversion of 100 %, total reducing sugar and glucose yields at 92.2 % and over 85 % is achieved in the aqueous system with FS90@C/HPW12 and 5 mmol/L H2SO4. FS90@C/HPW12 also exhibits good reusability in multiple hydrolysis. This research provides a particular way for the design and synthesis of solid catalysts to induce the highly efficient hydrolysis of cellulose to sugar by chemical catalysis in a full aqueous system.

Isolation, screening and characterization of efficient cellulose-degrading fungal and bacterial strains and preparation of their consortium under in vitro studies.

In this investigation, cellulose-degrading fungi and bacteria were isolated from different partially decomposed cellulose-rich substrates, such as groundnut residues, rice straw, and rotten wood, following dilution plating techniques on carboxymethyl cellulose agar media and screening for potential cellulose degradation ability. The development of a clear halo zone surrounding the microbial colonies during the initial screening process using the Congo red test (20 isolates) suggested cellulose hydrolysis, and the highest cellulase production activity was implied by the isolates with the largest clear zone ratio (9 isolates). Using both macroscopic and microscopic examinations, as well as standard biochemical tests outlined in Bergey's Manual of Determinative Bacteriology, the genus-level identification of fungi and bacteria was accomplished. In order to molecularly identify the 4 isolatedfungal and bacterial strains at the species level after being ultimately selected for cellulase production potential under in vitro studies, fungal and bacterial DNA was extracted and amplified by PCR using the universal primers ITS1 and ITS4 for fungi (ITS rRNA, 5.8S rRNA) and 8F and 1492R for bacterial isolates (16S rRNA). After sequencing, the PCR results were compared to other comparable sequences in GenBank (NCBI). Based on the available NCBI data, phylogenetic analysis of their ribosomal gene partial sequences revealed that DAJ2 (PP086700) shares 100% homology with Aspergillus foetidus, DTJ4 (PP086699) shares 99.74% similarity with Trichoderma atrobrunnium, DBJ6 (PP082584) shares 100% identity with Priestia megaterium, and DMB9 (PP082585) shares 99.88% homology with Micrococcus yunnanensis. The cellulolytic potential of Phanerochaete chrysosporium is well established. Therefore, it was considered a standard culture for comparison and was collected from the MTCC, Chandigarh, India. Overall, all 4 selected isolates and the check organism were mutually compatible or synergistic with each other, and their consortium is useful for the accelerated decomposition of organic constituents during rapid composting.

Wet torrefaction of biomass waste into high quality hydrochar and value-added liquid products using different zeolite catalysts

Wet torrefaction (WT) proves to be a highly efficient pretreatment method for biomass waste, resulting in the production of hydrochar and valuable liquid products. In this study, a groundbreaking chemocatalytic approach is introduced, employing various zeolite catalysts (H-ZSM-5, H-Beta, H–Y, H-USY, and H-Mordenite) in a batch reactor under a nitrogen atmosphere. This method enables the simultaneous one-pot production of levulinic acid (LA) and/or bio-ethanol during the WT process of wood cellulose pulp residue (WCPR), ultimately yielding high-quality solid fuel. The WT process involves at 220 and 260 °C, H2O/WCPR = 10, and torrefaction time at 15, 30 and 60 min. The study identifies that at 220 °C and 15 min, as the optimal temperature and time, for bio-ethanol production, achieving a selectivity of 59.0 % with the H–Y catalyst, while the highest amount of bio-ethanol (75.6 %) was detected in presence of H-USY zeolite at 260 °C after 60 min. In addition, it was found the formation of relatively high amount of LA (62.0 %) at 220 °C after 60 min but using the H-ZSM-5 catalyst. For the WT + Mordenite sample (220 °C, 60 min), the highest carbon content of 71.5 % is achieved, resulting in the higher heating value (HHV) of 27.3 MJ/kg, an enhancement factor of 1.36, and carbon enrichment of 1.48, with the sequence of element removal during WT prioritized as DO > DH > DC and the weight loss of 68 %. Finally, the reaction mechanism was proposed to elucidate the formation of liquid products after WT of WCPR with participation of zeolite catalysts. The main pathway involving the direct conversion of cellulose into hydroxyacetone, followed by the subsequent generation of ethanol through the C–C cleavage of hydroxyacetone while LA formed via well-known route which includes cellulose hydrolysis to form glucose, conversion to 5-HMF and the subsequent transformation of 5-HMF into LA.

Impact of aleatory and epistemic uncertainties on thermal risk and production assessment: Application to the hydrogenation of levulinic acid and butyl levulinate

The hydrogenation of levulinates, derivatives from cellulose hydrolysis, leads to the platform molecule γ-valerolactone (GVL). While prior investigations indicate the propensity for thermal runaways in this reaction, a comprehensive sensitivity analysis has been conspicuously absent in the existing literature. This study endeavors to scrutinize the influence of input parameters on both thermal risks and the production rate during GVL synthesis. Distinguished by its dual focus on sensitivity analyses, this manuscript also contrasts the implications of aleatory and epistemic uncertainties on thermal risk and production metrics. Aleatory uncertainties arise from the inherent variability of initial conditions, while epistemic uncertainties emanate from incomplete knowledge of the kinetic model. Employing Sobol global sensitivity analysis on the kinetic model, we delineate the hierarchical importance of various parameters. This analysis incorporates a quantification of uncertainty, and algorithmic approaches are proffered. The findings reveal that the initial temperature, the initial mass of the Ru/C catalyst, and hydrogen pressure are pivotal factors that are directly proportional to thermal risk and production efficiency. The implications of uncertainty on these variables are also discussed.

Green ecofriendly enhancement of cellulase productivity using agricultural wastes by Aspergillus terreus MN901491: statistical designs and detergent ability on cotton fabrics

BackgroundCellulase is considered a group member of the hydrolytic enzymes, responsible for catalyzing the hydrolysis of cellulose and has various industrial applications. Agricultural wastes are used as an inexpensive source for several utilizable products throughout the world. So, searching for cellulase enzymes from fungal strains capable of utilizing agricultural wastes to increase productivity, reduce costs and overcome waste accumulation in the environment is very important to evaluate its potency as a bio-additive to detergent agents.ResultsIn the current study, the previously identified fungal strain Aspergillus terreus MN901491 was screened and selected for cellulase production. Medium parameters were optimized using one-factor-at-a-time (OFAT) and multi-factorial (Plackett-Burman and Box-Behnken) design methods. OFAT showed the ability of the fungal strain to utilize agricultural wastes (corn cob and rice straw) as a substrate. Also, yeast extract was the best nitrogen source for enhancing cellulase productivity. The most significant variables were determined by Plackett-Burman Design (PBD) and their concentrations were optimized by Response Surface Methodology (RSM) using Box-Behnken Design (BBD). Among eleven independent variables screened by PBD, malt extract, (NH4)2SO4, and KCl were the most significant ones followed by rice straw which affected cellulase production positively. The ANOVA results particularly the R2-value of PBD (0.9879) and BBD (0.9883) confirmed the model efficiency and provided a good interpretation of the experiments. PBD and BBD improved cellulase productivity by 6.1-fold greater than that obtained from OFAT. Medium optimization using OFAT and statistical models increased cellulase production from A. terreus MN901491 by 9.3-fold compared to the non-optimized medium. Moreover, the efficiency of cellulase activity on cotton fabrics as a bio-additive detergent was evaluated and estimated using whiteness and scanning electron microscope (SEM) that affirmed its potential effect and remarkable detergent ability to improve whiteness by 200% in comparison with non-washed fabric and by 190% in comparison with fabric washed by water.ConclusionThe presented work was stabilized as a multi-efficiency in which wastes were used to produce cellulase enzyme from the fungal strain, Aspergillus terreus MN901491 as a bio-additive to detergent applications that involved ecofriendly and green processes.

Full utilization of poplar sawdust with chemical-mechanical pretreatment for coproduction of xylooligosaccharides, fermentable sugars and porous carbon materials

In recent decades, one of the major challenges of biorefinery is the full utilization of lignocellulosic components for coproduction of value-added materials. In this context, we proposed an integrated process of acetic acid (AC) pretreatment, Papir Forsknings Institutet (PFI) refining and enzymatic hydrolysis to coproduce xylooligosaccharides, fermentable sugars and lignin-based porous carbon materials. Results showed AC pretreatment (170 ºC, 60 min, 5 w/v % acetic acid and 5% 2-naphthol addition based on dry mass of biomass) resulted in maximum xylooligosaccharids (XOS) yield of 51.08%. The integrated process of AC pretreatment assisted by 2-naphthol-7-sulfonate addition and PFI post-refining led to cellulose hydrolysis yield of 98.20% and lignin-based porous carbon materials with methylene blue adsorption capacity of up to 749.17 mg/g. Moreover, it was found lignin repolymerization inhibitors (i.e. 2-naphthol, 2-naphthol-7-sulfonate) in acid pretreatment helped increase the specific surface area of substrate and decrease surface lignin coverage, which enhanced cellulose accessibility to cellulase enzymes. Moreover, they enhanced lignin detaching during enzymatic hydrolysis, which reduced cellulase aggregation and promoted the ease of cellulose hydrolysis. Results demonstrated an efficient pretreatment strategy to maximize coproduction of xylooligosaccharids, fermentable sugars and lignin materials from lignocellulosic biomass for full utilization.

A New Bacillus velezensis Strain CML532 Improves Chicken Growth Performance and Reduces Intestinal Clostridium perfringens Colonization.

Bacillus velezensis has gained increasing recognition as a probiotic for improving animal growth performance and gut health. We identified six B. velezensis strains from sixty Bacillus isolates that were isolated from the cecal samples of fifteen different chicken breeds. We characterized the probiotic properties of these six B. velezensis strains. The effect of a selected strain (B. velezensis CML532) on chicken growth performance under normal feeding and Clostridium perfringens challenge conditions was also evaluated. The results revealed that the six B. velezensis strains differed in their probiotic properties, with strain CML532 exhibiting the highest bile salt and acid tolerance and high-yield enzyme and antibacterial activities. Genomic analyses showed that genes related to amino acid and carbohydrate metabolism, as well as genes related to starch and cellulose hydrolysis, were abundant in strain CML532. Dietary supplementation with strain CML532 promoted chicken growth, improved the gut barrier and absorption function, and modulated the gut microbiota. Under the C. perfringens challenge condition, strain CML532 alleviated intestinal damage, reduced ileal colonization of C. perfringens, and also improved chicken growth performance. Collectively, this study demonstrated that the newly isolated B. velezensis strain is a promising probiotic with beneficial effects on chicken growth performance and gut health.

A Green Nanocatalyst for Fatty Acid Methyl Ester Conversion from Waste Cooking Oil

This study used a novel combination of cellulose nanocrystals (CNCs) and calcium oxide (CaO) nanocomposite (CaO/CNCs) for the production of biodiesel from waste cooking oil. The filter paper was used as a raw cellulose source to produce the CNCs from the acid hydrolysis of cellulose with sulfuric acid. The as-synthesized CaO/CNC nanocomposite is recyclable and environmentally friendly and was characterized using Fourier transform infrared spectroscopy, energy dispersive X-ray, scanning electron microscopy, and X-ray diffraction. The optimum process parameters investigated are a 20:1 methanol-to-oil molar ratio, 3-weight percent catalyst concentration, 60 °C temperature, and 90 min of reaction time. Under the optimum conditions, a biodiesel yield of 84% was obtained. The CaO/CNC nanocomposite achieved five times reusability, indicating its effectiveness and reusability in the transesterification reaction. The synthesized biodiesel chemical composition was examined using FTIR, GCMS, 1H-NMR, and 13C-NMR, and its properties, including specific gravity, color, flash point, cloud point, pour point, viscosity, sulfur content, sediments, water content, total acid number, cetane number, and corrosion test, were ascertained using ASTM standard practices. The outcomes were determined to fulfill global biodiesel standards (ASTM 951, 6751). Five successive transesterification processes were used to test the regeneration of the catalyst; the first three showed no distinct change, while the fifth cycle showed a reduction of up to 79%. The innovative composite CaO/CNC and used cooking oil are stable, affordable, and extremely successful for long-term biodiesel generation.

Engineering Compositionally Uniform Yeast Whole-Cell Biocatalysts with Maximized Surface Enzyme Density for Cellulosic Biofuel Production.

In recent decades, whole-cell biocatalysis has played an increasingly important role in the food, pharmaceutical, and energy sector. One promising application is the use of ethanologenic yeast displaying minicellulosomes on the cell surface to combine cellulose hydrolysis and fermentation into a single step for consolidated bioprocessing. However, cellulosic ethanol production using existing yeast whole-cell biocatalysts (yWCBs) has not reached industrial feasibility due to their inefficient cellulose hydrolysis. As prior studies have demonstrated enzyme density on the yWCB surface to be one of the most important parameters for enhancing cellulose hydrolysis, we sought to maximize this parameter at both the population and single-cell levels in yWCBs displaying tetrafunctional minicellulosomes. At the population level, enzyme density is limited by the presence of a nondisplay population constituting 25-50% of all cells. In this study, we identified the cause to be plasmid loss and successfully eliminated the nondisplay population to generate compositionally uniform yWCBs. At the single-cell level, we demonstrate that enzyme density is limited by molecular crowding, which hinders minicellulosome assembly. By adjusting the integrated gene copy number, we obtained yWCBs of tunable enzyme display levels. This tunability allowed us to avoid the crowding-limited regime and achieve a maximum enzyme density per cell. As a result, the best strain showed a cellulose-to-ethanol yield of 4.92 g/g, corresponding to 96% of the theoretical maximum and near-complete conversion (∼96%) of the starting cellulose (1% PASC). Our holistic engineering strategy that combines a population and single-cell level approach is broadly applicable to enhance the WCB performance in other biocatalytic cascade schemes.

The influence of reed nanocellulose on the quality indicators of paper-basis for wallpapers

Improving the production technology of products with improved quality indicators and with less impact on the environment remains an urgent scientific and practical problem of paper industry enterprises. This refers to the technology for the production of paper-bases for wallpaper using environmentally safe chemical additives, in particular nanocellulose (NC), which was obtained by acid hydrolysis from reed cellulose. The production of cellulose was carried out in two stages - extraction from reed stalks with a solution of alkali and an organosolvent method of cooking in a solution of peracetic acid. The obtained organosolvent cellulose contained the remains of lignin and mineral substances, which allows it to be used for the preparation of NC. As a result of the hydrolysis of organosolvent cellulose, a time-stable NC suspension was extracted, the properties of which were investigated by scanning electron microscopy (morphological changes in the structure of reed cellulose-containing materials), atomic force microscopy (determination of topographic characteristics of NC), analysis of electronic absorption spectra (transparency of NC films). It was established that reed NC films had nanoparticles with a cross-sectional size of 5-25 nm, density up to 1.52 g/cm3, transparency up to 81.6 %, tensile strength up to 65 MPa. For the production of castings of paper-bases for wallpaper samples, sulfated pine bleached cellulose and polyester synthetic fiber were used, to the fibrous mass of which were added the following chemical additives: alkyl ketene dimer, reed NC, binder, and optical brightener. It has been shown that the use of nanocellulose at a rate of 0.35 % to 1.0 % of the paper mass leads to a significant improvement in the physical and mechanical quality indicators of the paper base for wallpaper. It was established that the replacement of 50 % of the synthetic chemical auxiliary substance alkyl ketene dimer with nanocellulose or additional application of nanocellulose at a rate of 0.5 g/m2 on the surface of the casting with 0.7 % alkyl ketene dimer allows to obtain paper that meets the requirements of the standard. The obtained results indicate the prospects of using reed nanocellulose for the production of other mass types of paper and cardboard.

Self-Buffering system for Cost-Effective production of lactic acid from glucose and xylose using Acid-Tolerant Issatchenkia orientalis

This study presents a cost-effective strategy for producing organic acids from glucose and xylose using the acid-tolerant yeast, Issatchenkia orientalis. I. orientalis was engineered to produce lactic acid from xylose, and the resulting strain, SD108XL, successfully converted sorghum hydrolysates into lactic acid. In order to enable low-pH fermentation, a self-buffering strategy, where the lactic acid generated by the SD108XL strain during fermentation served as a buffer, was developed. As a result, the SD108 strain produced 67 g/L of lactic acid from 73 g/L of glucose and 40 g/L of xylose, simulating a sugar composition of sorghum biomass hydrolysates. Moreover, techno-economic analysis underscored the efficiency of the self-buffering strategy in streamlining the downstream process, thereby reducing production costs. These results demonstrate the potential of I. orientalis as a platform strain for the cost-effective production of organic acids from cellulosic hydrolysates.

Pressure-assisted hydrothermal pretreatment for biorefinery to enhance pulp production

The efficient removal of hemicelluloses while preventing cellulose hydrolysis is crucial in Kraft pulping yet remains challenging. Herein, a mild pressure-assisted hydrothermal pretreatment strategy was developed in this study prior to Kraft pulping. Research indicated that pretreatment at 155 °C under 3 MPa pressure significantly enhances hemicelluloses removal (to 70.63 %), surpassing even that at 165 °C under ambient pressure. Moreover, during pre-hydrolysis Kraft pulping, pressure-assisted hydrothermal pretreatment could reduce the concentration of active alkali used in the subsequent pulping process. The cellulose properties (viscosity = 491 ml/g) and purity (R10 = 94.60 %) of bleached pulp obtained from pressure-assisted hydrothermal pretreatment outperform those obtained from conventional hydrolysis. Furthermore, the removed hemicelluloses were converted into monosaccharides and polysaccharides to produce high-value chemicals in downstream processes. Therefore, pressure-assisted hydrothermal pretreatment not only enhanced hemicelluloses removal and pulp properties but also reduced alkali concentration in the subsequent pulping process, promoting sustainable development in pulp production.

Microwave-enhanced hydrolysis of cellulose by acidic ionic liquids

In the [Bmim]Cl reaction medium, five different acidic ionic liquids were used as catalysts to study the effects of reaction time, reaction temperature, system water content, catalyst dosage, microwave power, and other factors on cellulose hydrolysis under microwave irradiation. The results showed that in the [Bmim]Cl reaction system, using N-methylpyrrolidone methylsulfonic acid salt as a catalyst, controlling the microwave reaction time at 10 min, reaction temperature at 130 °C, catalyst dosage at 1 g/g (cellulose), water addition at 0.756 μL/g ([Bmim]Cl), and microwave power at 480 W, resulted in the best cellulose hydrolysis effect with a glucose yield of 74.49%. Compared to conventional heating, the glucose yield increased by 24% and the hydrolysis time was reduced by 77%. Microwave irradiation significantly enhances the cellulose hydrolysis process in an ionic liquid medium.

Modulation of sulfur-containing groups in the carbon skeleton of solid acids by liquid sulfur carbonization to promote cellulose hydrolysis

Improving carbon skeleton structure of solid acids is essential to enhance their hydrolysis activity. In this work, sulfur-modified solid acid was prepared by liquid sulfur carbonization for the hydrolysis of cellulose. The liquid sulfur environment makes the cellulose adequate contact with sulfur during the carbonization process, which is beneficial for the entry of sulfur into the carbon skeleton. Sulfur is doped into the solid acids in various forms and the forms and content of sulfur-containing groups in the solid acids were successfully regulated by adjusting the ratio of cellulose to sulfur. As the ratio of cellulose to sulfur increases, the different sulfur-containing groups show regular changes, influencing hydrolysis activity. Because of hydrogen bonding between SO and cellulose, SO3H group is more accessible to the cellulose which leads to a significant increase in the hydrolysis activity of the solid acid.

Tailoring whole slurry bioprocessing for sugary stovers to augment sugar production by integrating soluble and insoluble carbohydrates

Obtaining sufficient concentrations of fermentable sugars from the polysaccharides of lignocellulosic materials represents a long-term challenge in achieving sustainable biorefineries. This work aimed to enhance sugar titers by employing high sugar-containing stovers (HSS) and combining its intrinsic soluble sugars with the two insoluble carbohydrates, namely cellulose and hemicellulose. Whole-slurry hydrolysis (WSH) was performed under low-to-high solid conditions using non-detoxified pretreated slurry, which exhibited a decrease in cellulose hydrolysis efficiency (CHE) from 89.08% to 42.1% as the solid loadings increased from 7% to 20%. A further WSH with detoxified slurry showed a significant increase in CHE from 42.1% to 59.52% at 20% solid loading, indicating that inhibitors present in the pretreated slurry had negative effects on CHE. Lower CHE with non-detoxified slurry accompanied by higher losses of cellulase and β-glucosidase activities, particularly at higher solid loadings. Therefore, systematic modification of WSH was performed by incorporating 2% syringic acid during pretreatment and 0.4% polyethylene glycol during saccharification, reformulating enzyme cocktails, and implementing a fed-batch experiment. These modifications resulted in a notable improvement in sugar production under high-solid loading (20%) and non-detoxified conditions, reaching 142.87 g/L total sugars with a CHE of 90.7%. These findings have revealed the potential of integrating soluble sugars with holocellulose for obtaining high-titer fermentable sugars in lignocellulosic biorefineries.

An experimental and modeling approach to describe the deactivation of cellulases at the air-liquid interface.

Understanding the reaction mechanisms involved in the enzymatic hydrolysis of cellulose is important because it is kinetically the most limiting step of the bioethanol production process. The present work focuses on the enzymatic deactivation at the air-liquid interface, which is one of the aspects contributing to this global deactivation. This phenomenon has already been experimentally proven, but this is the first time that a model has been proposed to describe it. Experiments were performed by incubating Celluclast cocktail solutions on an orbital stirring system at different enzyme concentrations and different surface-to-volume ratios. A 5-day follow-up was carried out by measuring the global FPase activity of cellulases for each condition tested. The activity loss was proven to depend on both the air-liquid surface area and the enzyme concentration. Both observations suggest that the loss of activity takes place at the air-liquid surface, the total amount of enzymes varying with volume or enzyme concentration. Furthermore, tests performed using five individual enzymes purified from aTrichoderma reesei cocktail showed that the only cellulase that is deactivated at the air-liquid interface is cellobiohydrolaseII. From the experimental data collected by varying the initial enzyme concentration and the ratio surface to volume, it was possible to develop, for the first time, a model that describes the loss of activity at the air-liquid interface for this configuration.

Hydrolysis of Cellulose using boronic-acid multifunctional carbocatalysts

Background Developingeffective and sustainable catalysts for cellulose hydrolysis is crucial for transforming this abundant biopolymer into renewable chemicals and biofuel. Carbonaceous solid acids are promising catalysts for this reaction due to their low cost, chemical and hydrothermal stability, tunable surface, and high affinity for cellulose. MethodsWe developed multifunctional carbocatalysts for cellulose hydrolysis by introducing boronic groups and weak acid sites along with high-density sulfonic acid through borylation of mesophase pitch carbon (MPC) followed by sulfonation. The functionalized MPC was characterized using various techniques, including FT-IR, XPS, SS-NMR, Raman spectroscopy, and TGA. Significant findingsThe results of surface characterization revealed the successful introduction of multifunctional groups on the peripheral surface of MPC. This carbocatalyst can effectively hydrolyze pretreated cellulose into glucose, resulting in a maximum yield of 64 % in water at 180 °C for 3 h. Boronic groups and weak acid sites could mediate the interaction of cellulose molecules with catalyst surface to enhance the catalytic hydrolysis. The apparent activation energy for breaking the glycosidic bonds using the functionalized MPC is 99 kJ/mol, which is lower than the one derived from homogeneous acids. Furthermore, the carbocatalyst is recyclable at least four cycles prior to the significant loss for reactivity.

Natronoglomus mannanivorans gen. nov., sp. nov., beta-1,4-mannan utilizing natronoarchaea from hypersaline soda lakes.

Beta-mannans are insoluble plant polysaccharides with beta-1,4-linked mannose as the backbone. We used three forms of this polysaccharide, namely, pure mannan, glucomannan, and galactomannan, to enrich haloarchaea, which have the ability to utilize mannans for growth. Four mannan-utilizing strains obtained in pure cultures were closely related to each other on the level of the same species. Furthermore, another strain selected from the same habitats with a soluble beta-1,4-glucan (xyloglucan) was also able to grow with mannan. The phylogenomic analysis placed the isolates into a separate lineage of the new genus level within the family Natrialbaceae of the class Halobacteria. The strains are moderate alkaliphiles, extremely halophilic, and aerobic saccharolytics. In addition to the three beta-mannan forms, they can also grow with cellulose, xylan, and xyloglucan. Functional genome analysis of two representative strains demonstrated the presence of several genes coding for extracellular endo-beta-1,4-mannanase from the GH5_7 and 5_8 subfamilies and the GH26 family of glycosyl hydrolases. Furthermore, a large spectrum of genes encoding other glycoside hydrolases that were potentially involved in the hydrolysis of cellulose and xylan were also identified in the genomes. A comparative genomics analysis also showed the presence of similar endo-beta-1,4-mannanase homologs in the cellulotrophic genera Natronobiforma and Halococcoides. Based on the unique physiological properties and the results of phylogenomic analysis, the novel mannan-utilizing halolarchaea are proposed to be classified into a new genus and species Natronoglomus mannanivorans gen. nov., sp. nov. with the type strain AArc-m2/3/4 (=JCM 34861=UQM 41565).

Zeolite-assisted acid hydrolysis of cellulose: Optimization of reaction conditions and chemical pretreatments for enhancing HMF yields

This study explores the hydrolysis of microcrystalline cellulose under soft conditions using a combination of both homogeneous (HCl) and heterogeneous catalysts (β-zeolite). The impact of temperature and HCl concentration is studied, revealing that the most favorable results (highest HMF yield) are achieved at 140ºC with 0.02 %w/w of HCl (19% of selectivity, 23.5% of conversion). Nevertheless, the inherent recalcitrance of cellulose limits the conversion and the HMF concentration. Three chemical pretreatments (HCl, H2O2, HNO3) are considered, assessing the effect of concentration. Except when using 69% of HNO3, the bulk structure of cellulose remains largely unaffected (low effect on conversions). However, the surface of cellulose undergoes chemical alteration due to the acidic and predominantly oxidizing pretreatment, leading to the detection of C5 compounds. These modifications have a positive influence on the reaction, significantly enhancing the selectivity towards HMF up to 50% (34% of conversion).