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Title: Hydroxy sulfonic acid catalyzed hydrolysis of cellulose
Development of efficient catalytic methods for the hydrolysis of cellulose is a major research challenge in sustainable biofuel and polymer areas. In this study five hydroxy sulfonic acids were studied as simple model compounds for cellulase enzyme for the hydrolysis of cellulose. The catalytic activities were measured by analysis of total reducing sugar (TRS) yields produced in a series of reactions carried out at 150–190 °C using 0.050 M aqueous hydroxy sulfonic acid solutions. The highest catalytic activity was observed with isethionic acid, producing 62.7% TRS yield at 180 °C after 4 hr. In the second phase of the work, Density Functional Theory (DFT) calculations were used to study the interactions between hydroxy sulfonic acids and cellulose model compound D-cellobiose to supplement the experimental results. The D-cellobiose – hydroxy sulfonic binding energies and the distance between glycosidic oxygen and -SO3H acidic H were evaluated and the -SO3H to glycosidic oxygen distance was identified as the more important parameter co-related to the catalytic activity. The isethionic acid with highest cellulose hydrolysis activity showed the shortest -SO3H to glycosidic oxygen distance of 1.744 Å. more »« less
Fernando, Harshica; Amarasekara, Ananda S.(
, Current Organocatalysis)
Background:
Polycarboxylic acids are of interest as simple mimics for cellulase enzyme catalyzed depolymerization of cellulose. In this study, DFT calculations were used to investigate the effect of structure on dicarboxylic acid organo-catalyzed hydrolysis of cellulose model compound D-cellobiose to D-glucose.
Methods:
Binding energy of the complex formed between D-cellobiose and acid (Ebind), as well as glycosidic oxygen to dicarboxylic acid closest acidic H distance were studied as key parameters affecting the turn over frequency of hydrolysis in water.
Result:
α-D-cellobiose - dicarboxylic acid catalyst down face approach showed high Ebind values for five of the six acids studied; indicating the favorability of down face approach. Maleic, cis-1,2-cyclohexane dicarboxylic, and phthalic acids with the highest catalytic activities showed glycosidic oxygen to dicarboxylic acid acidic H distances 3.5-3.6 Å in the preferred configuration.
Conclusion:
The high catalytic activities of these acids may be due to the rigid structure, where acid groups are held in a fixed geometry.
Fernando, Harshica; Amarasekara, Ananda S.(
, European Journal of Organic Chemistry)
Abstract
Understanding interactions of metal ions with cellulose is an important step in the development of efficient catalytic methods for processing cellulose. In this study, density functional theory methods were used to identify oxygen atoms interacting or chelating with selected metal chlorides of Li+, K+, Mg2+, Ca2+, Sn2+, Zn2+and La3+with cellulose model compound D‐cellobiose. Calculated metal‐oxygen distances of energy minimized D‐cellobiose : metal chloride 1 : 2 mixtures revealed that the metal ions approach between the two glucose rings in α/β‐D‐cellobiose, and O4, O9are the preferred interaction/chelation points. DFT study supported a previous13C NMR chemical shift change based experiments. ZnCl2showing the shortest metal‐oxygen distances in approach to α/β D‐cellobiose is known to produce the largest13C NMR chemical shift changes in D‐cellobiose. In α‐anomer, average closest metal‐oxygen distances and NMR shift changes co‐related at 95 % confidence interval with liner regression R2=0.8582 and Sy.x=0.5722.
Zeolites (ZSM-5 and Beta) with different SiO2/Al2O3 ratios were synthesized as solid acids for hydrolyzing cellulose in an inorganic ionic liquid system (lithium bromide trihydrate solution, LBTH) under mild conditions. The results indicated that the texture properties of zeolite had little effect on catalytic activity, while acidity of zeolite was crucial to the cellulose hydrolysis. In the LBTH system, H-form zeolites released H+ into the solution from their acid sites via ion-exchange with Li+, which hydrolyzed the cellulose already dissolved. This unique homogeneous hydrolysis mechanism was the primary reason for the excellent performance of the zeolites in catalyzing cellulose hydrolysis in the LBTH system. It was found cellulose could be completely hydrolyzed to glucose and oligoglucan by 2% (w/w on cellulose) zeolite at 140 °C within 3 h with a single-pass glucose yield 61%. The zeolites could be recovered with 50% initial catalytic activity after regeneration and reused with stable catalytic activity.
Recently, we reported the discovery of a novel endoglucanase of the glycoside hydrolase family 12 (GH12), designated IfCelS12A, from the haloalkaliphilic anaerobic bacteriumIocasia fonsfrigidaestrain SP3-1, which was isolated from a hypersaline pond in the Samut Sakhon province of Thailand (ca. 2017). IfCelS12A exhibits high substrate specificity on carboxymethyl cellulose and amorphous cellulose but low substrate specificity on b-1,3;1,4-glucan. Unlike some endoglucanases of the GH12 family, IfCelS12A does not exhibit hydrolytic activity on crystalline cellulose (i.e., Avicel™). High-Pressure Liquid Chromatography (HPLC) and Thin Layer Chromatography (TLC) analyses of products resulting from IfCelS12-mediated hydrolysis indicate mode of action for this enzyme. Notably, IfCelS12A preferentially hydrolyzes cellotetraoses, cellopentaoses, and cellohexaoses with negligible activity on cellobiose or cellotriose. Kinetic analysis with cellopentaose and barely b-d-glucan as cellulosic substrates were conducted. On cellopentaose, IfCelS12A demonstrates a 16-fold increase in activity (KM = 0.27 mM;kcat = 0.36 s−1;kcat/KM = 1.34 mM−1s−1) compared to the enzymatic hydrolysis of barley b-d-glucan (KM: 0.04 mM,kcat: 0.51 s−1,kcat/KM = 0.08 mM−1s−1). Moreover, IfCelS12A enzymatic efficacy is stable in hypersaline sodium chlorids (NaCl) solutions (up to 10% NaCl). Specifically, IfCel12A retains notable activity after 24 h at 2M NaCl (10% saline solution). IfCelS12A used as a cocktail component with other cellulolytic enzymes and in conjunction with mobile sequestration platform technology offers additional options for deconstruction of ionic liquid–pretreated cellulosic feedstock.
Key points
•IfCelS12A from an anaerobic alkaliphile Iocasia fronsfrigidae shows salt tolerance
•IfCelS12A in cocktails with other enzymes efficiently degrades cellulosic biomass
•IfCelS12A used with mobile enzyme sequestration platforms enhances hydrolysis
Background Cellulolytic, hemicellulolytic, and amylolytic (CHA) enzyme-producing halophiles are understudied. The recently defined taxon Iocasia fonsfrigidae consists of one well-described anaerobic bacterial strain: NS-1 T . Prior to characterization of strain NS-1 T , an isolate designated Halocella sp. SP3-1 was isolated and its genome was published. Based on physiological and genetic comparisons, it was suggested that Halocella sp. SP3-1 may be another isolate of I. fronsfrigidae . Despite being geographic variants of the same species, data indicate that strain SP3-1 exhibits genetic, genomic, and physiological characteristics that distinguish it from strain NS-1 T . In this study, we examine the halophilic and alkaliphilic nature of strain SP3-1 and the genetic substrates underlying phenotypic differences between strains SP3-1 and NS-1 T with focus on sugar metabolism and CHA enzyme expression. Methods Standard methods in anaerobic cell culture were used to grow strains SP3-1 as well as other comparator species. Morphological characterization was done via electron microscopy and Schaeffer-Fulton staining. Data for sequence comparisons ( e.g. , 16S rRNA) were retrieved via BLAST and EzBioCloud. Alignments and phylogenetic trees were generated via CLUTAL_X and neighbor joining functions in MEGA (version 11). Genomes were assembled/annotated via the Prokka annotation pipeline. Clusters of Orthologous Groups (COGs) were defined by eegNOG 4.5. DNA-DNA hybridization calculations were performed by the ANI Calculator web service. Results Cells of strain SP3-1 are rods. SP3-1 cells grow at NaCl concentrations of 5-30% (w/v). Optimal growth occurs at 37 °C, pH 8.0, and 20% NaCl (w/v). Although phylogenetic analysis based on 16S rRNA gene indicates that strain SP3-1 belongs to the genus Iocasia with 99.58% average nucleotide sequence identity to Iocasia fonsfrigida NS-1 T , strain SP3-1 is uniquely an extreme haloalkaliphile. Moreover, strain SP3-1 ferments D-glucose to acetate, butyrate, carbon dioxide, hydrogen, ethanol, and butanol and will grow on L-arabinose, D-fructose, D-galactose, D-glucose, D-mannose, D-raffinose, D-xylose, cellobiose, lactose, maltose, sucrose, starch, xylan and phosphoric acid swollen cellulose (PASC). D-rhamnose, alginate, and lignin do not serve as suitable culture substrates for strain SP3-1. Thus, the carbon utilization profile of strain SP3-1 differs from that of I. fronsfrigidae strain NS-1 T . Differences between these two strains are also noted in their lipid composition. Genomic data reveal key differences between the genetic profiles of strain SP3-1 and NS-1 T that likely account for differences in morphology, sugar metabolism, and CHA-enzyme potential. Important to this study, I. fonsfrigidae SP3-1 produces and extracellularly secretes CHA enzymes at different levels and composition than type strain NS-1 T . The high salt tolerance and pH range of SP3-1 makes it an ideal candidate for salt and pH tolerant enzyme discovery.
@article{osti_10426177,
place = {Country unknown/Code not available},
title = {Hydroxy sulfonic acid catalyzed hydrolysis of cellulose},
url = {https://par.nsf.gov/biblio/10426177},
DOI = {10.1080/17597269.2023.2221969},
abstractNote = {Development of efficient catalytic methods for the hydrolysis of cellulose is a major research challenge in sustainable biofuel and polymer areas. In this study five hydroxy sulfonic acids were studied as simple model compounds for cellulase enzyme for the hydrolysis of cellulose. The catalytic activities were measured by analysis of total reducing sugar (TRS) yields produced in a series of reactions carried out at 150–190 °C using 0.050 M aqueous hydroxy sulfonic acid solutions. The highest catalytic activity was observed with isethionic acid, producing 62.7% TRS yield at 180 °C after 4 hr. In the second phase of the work, Density Functional Theory (DFT) calculations were used to study the interactions between hydroxy sulfonic acids and cellulose model compound D-cellobiose to supplement the experimental results. The D-cellobiose – hydroxy sulfonic binding energies and the distance between glycosidic oxygen and -SO3H acidic H were evaluated and the -SO3H to glycosidic oxygen distance was identified as the more important parameter co-related to the catalytic activity. The isethionic acid with highest cellulose hydrolysis activity showed the shortest -SO3H to glycosidic oxygen distance of 1.744 Å.},
journal = {Biofuels},
author = {Amarasekara, Ananda S. and Nwankwo, Victor C. and Fernando, Harshica},
}
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