Xylanase effects on pulp delignification

Whitmire, David; Maiti, Biswajit

doi:10.1080/00986440211738

Cited by 5 publications

(4 citation statements)

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“…Experimental results and modeling of the process indicated an increased level of delignification with up to 48% lignin removal using a lower molecular weight xylanase. 11 In a kinetic study using a continuous stirred tank reactor, an accelerated delignification was achieved by the increased levels of oxygen pressure in alkaline delignification process. Analytical results indicated that adsorption of oxygen on the active aromatic lignin site follows a Langmuir-type behavior.…”

Section: Introductionmentioning

confidence: 99%

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

2015

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The kinetics of acid-catalyzed hemicellulose removal and also alkaline delignification of oat hull biomass were investigated. All three operational parameters namely, catalyst concentration (0.10-0.55 N H 2 SO 4 ), temperature (110-130 C), and residence time (up to 150 min) affected the efficiency of hemicellulose removal, with 100% of hemicellulose removed by appropriate selection of process parameters. Analysis of delignification kinetics (in the temperature range of 30-100 C) indicated that it can be expressed very well by a two-phase model for the crude biomass and also for the hemicellulose-prehydrolyzed material. The application of acid-catalyzed prehydrolysis improved the capacity of lignin dissolution especially at lower temperatures (30 and 65 C) and accelerated the dissolution of lignin. This acceleration of delignification by prehydrolysis was possible at all levels of temperature in the bulk phase; however, results were more significant at the lower temperatures in the terminal phase.

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Section: Introductionmentioning

confidence: 99%

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

2015

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“…In such a system, the concentration of the inhibitor can be kept at constant level, as it is diluted by constantly added fresh substrate, so the reaction rate is not greatly influenced by the inhibitor. Although semibatch systems [15][16][17] are not used for enzymatic reactions as often as membrane reactor systems, they may offer several advantages in comparison to the latter, e.g., simple construction, easy operation and easy process control.We are currently focusing on comparing the membrane reactor system with the semi-batch system for the enzymatic deacetylation of chitosan.…”

Section: Malgorzata M Jaworskamentioning

confidence: 99%

Chitin deacetylase product inhibition

Jaworska

2010

Biotechnology Journal

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Chitin deacetylase is the only known enzyme catalyzing the hydrolysis of the acetamino linkage in the N-acetylglucosamine units of chitin and chitosan. This reaction can play an important role in enzymatic production of chitosan from chitin, or in enzymatic modification of chitosan, which has applications in medicine, pharmacy or plant protection. It was previously shown that acetic acid, a product of the deacetylation process, may act as an inhibitor of chitin deacetylase. Here we show the mechanism of inhibition of chitin deacetylase isolated from Absidia orchidis vel coerulea by acetic acid released during the deacetylation process. The process follows competitive inhibition with respect to acetic acid with an inhibition constant of K(i) = 0.286 mmol/L. These results will help to find the optimal system to carry out the enzymatic deacetylation process for industrial applications.

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“…Quantifying the disparate nature of the transport and catalytic processes at different length scales would provide a key to the complete understanding of the depolymerization process. 11 Enzyme adsorption occurs on the external surface as well as on the pore surface of porous, amorphous xylan substrates, where Knudsen diffusion governs the transport of the enzyme molecules to the pore surface, 12 while the pore size distribution plays an important role in pore scale hydrolysis. 13 However, pretreatment of biomass alters the pore size distribution of the substrate, which in turn changes the diffusion dynamics of various molecules, resulting in hydrolysis rate and product yield.…”

Section: Introductionmentioning

confidence: 99%

Multiscale Dynamics of Hemicellulose Hydrolysis for Biofuel Production

Dutta

Chakraborty

2019

Ind. Eng. Chem. Res.

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Hemicelluloses are the earth's second most abundant structural polymers and are found in lignocellulosic biomass. This work uses a tightly coupled experimental and theoretical analysis to show that the enzymatic hydrolysis of hemicellulose is a two-phase multiscale reactive process, comprising the molecular scale, the pore scale, and the reactor scale. The pore scale is the smallest of these three scales, and the sequence of the length scales is given by reactor scale > molecular scale > pore scale. Enzyme adsorption to the solid xylan particles is the first important step in hemicellulose hydrolysis, followed by the cleaving of β-(1 → 4)-glycosidic bonds by an endoenzyme in solid and liquid phases. Our experiments show that enzyme adsorption and solid-phase hydrolysis primarily occur on the pore surface, with the former, though initially nonequilibrium, attaining equilibrium at 5 h. At the molecular scale, the products (xylose and xylobiose) inhibit the hydrolysis noncompetitively in both liquid-and solid-phase hydrolyses, and the nature of product inhibition remains unaltered by the mixing at the reactor scale. Model−experiment comparisons allow us to quantify the adsorption and desorption rate constants as well as the kinetic constants in the solid-and liquid-phase hydrolyses. The optimum solid loading is obtained as 5 mg/mL, above which substrate inhibition sets in. We develop an "optimal mixing" strategy comprising 55−70 min of initial reactor mixing followed by no mixing for the rest of the hydrolysis, which increases xylose and reducing sugar yields by 6.3−8% and 13−20%, respectively, over continuous mixing at 150 rpm for 1−5 mg/mL xylan, with an energy saving of 94−96% on reactor mixing over 24 h. We quantify the dominant phenomena and the determining timescales at each length scale, and we show that efficient depolymerization of solid carbohydrates results from coupled interscale interactions at various stages of the two-phase hydrolysis process.

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Xylanase effects on pulp delignification

Cited by 5 publications

References 0 publications

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

Chitin deacetylase product inhibition

Multiscale Dynamics of Hemicellulose Hydrolysis for Biofuel Production

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