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.
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The Effect of Dicarboxylic Acid Catalyst Structure on Hydrolysis of CelluloseModel Compound D-Cellobiose in Water
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.
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.
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.
The high catalytic activities of these acids may be due to the rigid structure, where acid groups are held in a fixed geometry.
- Award ID(s):
- 1704144
- NSF-PAR ID:
- 10483283
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- Current Organocatalysis
- Volume:
- 9
- Issue:
- 2
- ISSN:
- 2213-3372
- Page Range / eLocation ID:
- 163 to 171
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Recently, we reported the discovery of a novel endoglucanase of the glycoside hydrolase family 12 (GH12), designated IfCelS12A, from the haloalkaliphilic anaerobic bacterium
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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 -
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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.
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aims: Processing of cellulose can be used to produce value added renewable feedstock chemicals. background: Catalytic depolymerization and processing of cellulose can be used to produce value added renewable feedstock chemicals. objective: Development of an acidic ionic liquid - metal ion chloride catalyst system based single-reactor method for processing cellulose to value added products. method: The effect of metal chlorides as co-catalysts on 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid catalyzed degradation of cellulose in 40 % (v/v) aq. ethanol was studied by measuring levulinic acid, ethyl levulinate and 5-hydroxymethylfurfural yields. result: In experiments with Mn(II), Zn(II) chloride co-catalysts at 160 and 170 °C for 12 h, the initial yields of ethyl levulinate and 5-hydroxymethylfurfural improved from ~ 7 % to ~ 12-15% due to co-catalytic effects. The highest enhancements in ethyl levulinate yields were observed with CrCl3, where the yield increased from 6 to 27 % with the addition of 10 mol% co-catalyst. conclusion: All three transition metal chlorides studied produced improvements in yields of secondary products, ethyl levulinate and 5-hydroxymethylfurfural in acidic ionic liquid catalyzed degradation of cellulose in aqueous ethanol. The most significant enhancements in ethyl levulinate yields were observed with CrCl3 as a co-catalyst. other: nonemore » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2174/2213337208666211129090444
