Demonstration of pH control in a commercial immobilized glucose isomerase

Fournier, Ronald L.; Varanasi, Sasidhar; Byers, James P.; Chen, Guodong

doi:10.1002/(sici)1097-0290(19961220)52:6<718::aid-bit10>3.0.co;2-7

Cited by 11 publications

(7 citation statements)

References 10 publications

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“…We previously described a mathematical model (Byers et al, 1992) which demonstrated that the required pH gradient for a basic reaction (pH 7.5) could be achieved when an acidic reaction was carried out in a bulk solution of pH 4.5. Our experimental data (Byers et al, 1993;Chen et al, 1996;Chen et al, in press;Fournier et al, 1996) also showed that this pH control technique works well for that case. The objective of this article was to demonstrate, in theory, if it is still feasible to generate such a basic optimal pH microenvironment within an immobilized enzyme pellet for an enzyme that catalyzes an acid-generating reaction when this pellet is placed in a liquid phase solution whose pH is in the acidic range.…”

Section: Discussionsupporting

confidence: 70%

“…We have experimentally shown (Byers et al, 1993) that, with only about 10 mM of urea present in the acidic environment, a very thin immobilized urease membrane can not only separate an acidic environment (pH 4.5) from a basic environment (pH 7.5) but also maintain this large pH difference. We have further shown Fournier et al, 1996) that this technique allows a commercial immobilized glucose isomerase to have near optimal pH activity (pH 7.5) when immersed in a bulk solution of pH 4.6 in the presence of 20 mM urea. This technique effectively allows each reaction in the pathway to occur simultaneously, in proximity to each other, and at their respective optimal pH, thus solving the problem described before.…”

Section: Introductionmentioning

confidence: 86%

“…Using a compromised pH of 7.1 for this case, only about 30% of the maximal rate was obtained at 35°C (Anderson et al, 1992a). We have developed a pH control technique (Byers et al, 1992(Byers et al, , 1993Chen et al, 1996;Fournier et al, 1996;Chen et al, in press) for the problem illustrated above where sequential multistep synthesis reactions benefit by reaction pairing; however, the optimal pH for each step in the reaction pathway differs by several pH units. This technique involves the separation of the microenvironments of two steps of a synthesis reaction pathway by a thin immobilized urease layer that catalyzes the hydrolysis of urea.…”

Section: Introductionmentioning

confidence: 99%

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A mathematical model for the generation and control of a pH gradient in an immobilized enzyme system involving acid generation

Chen

Fournier

Varanasi

1998

Biotechnol. Bioeng.

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An optimal pH control technique has been developed for multistep enzymatic synthesis reactions where the optimal pH differs by several units for each step. This technique separates an acidic environment from a basic environment by the hydrolysis of urea within a thin layer of immobilized urease. With this technique, a two‐step enzymatic reaction can take place simultaneously, in proximity to each other, and at their respective optimal pH. Because a reaction system involving an acid generation represents a more challenging test of this pH control technique, a number of factors that affect the generation of such a pH gradient are considered in this study. The mathematical model proposed is based on several simplifying assumptions and represents a first attempt to provide an analysis of this complex problem. The results show that, by choosing appropriate parameters, the pH control technique still can generate the desired pH gradient even if there is an acid‐generating reaction in the system. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 394‐408, 1998.

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Section: Discussionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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A mathematical model for the generation and control of a pH gradient in an immobilized enzyme system involving acid generation

Chen

Fournier

Varanasi

1998

Biotechnol. Bioeng.

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“…In previous papers and patents, we have introduced our novel system and provided proof of concept for the co-immobilized enzyme pellet system [29,35,36,49,50]. In this paper, we present results of experiments that illustrate the effectiveness of our co-immobilized enzyme system for isomerization under conditions optimal for fermentation by common S. cerevisiae.…”

Section: Introductionmentioning

confidence: 98%

“…To overcome the disparity in the optimal pH's for the isomerization and fermentation, our group [29,35,36] proposed a novel scheme of isomerization that incorporates urease co-immobilized with xylose isomerase. This technique uses XI immobilized in a porous pellet for isomerization and the immobilized urease enzyme for pH control (Fig.…”

Section: Introductionmentioning

confidence: 99%

A Novel Technique that Enables Efficient Conduct of Simultaneous Isomerization and Fermentation (SIF) of Xylose

Rao

Chelikani

Relue

et al. 2008

Appl Biochem Biotechnol

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Of the sugars recovered from lignocellulose, D-glucose can be readily converted into ethanol by baker's or brewer's yeast (Saccharomyces cerevisiae). However, xylose that is obtained by the hydrolysis of the hemicellulosic portion is not fermentable by the same species of yeasts. Xylose fermentation by native yeasts can be achieved via isomerization of xylose to its ketose isomer, xylulose. Isomerization with exogenous xylose isomerase (XI) occurs optimally at a pH of 7-8, whereas subsequent fermentation of xylulose to ethanol occurs at a pH of 4-5. We present a novel scheme for efficient isomerization of xylose to xylulose at conditions suitable for the fermentation by using an immobilized enzyme system capable of sustaining two different pH microenvironments in a single vessel. The proof-of-concept of the two-enzyme pellet is presented, showing conversion of xylose to xylulose even when the immobilized enzyme pellets are suspended in a bulk solution whose pH is sub-optimal for XI activity. The co-immobilized enzyme pellets may prove extremely valuable in effectively conducting "simultaneous isomerization and fermentation" (SIF) of xylose. To help further shift the equilibrium in favor of xylulose formation, sodium tetraborate (borax) was added to the isomerization solution. Binding of tetrahydroxyborate ions to xylulose effectively reduces the concentration of xylulose and leads to increased xylose isomerization. The formation of tetrahydroxyborate ions and the enhancement in xylulose production resulting from the complexation was studied at two different bulk pH values. The addition of 0.05 M borax to the isomerization solution containing our co-immobilized enzyme pellets resulted in xylose to xylulose conversion as high as 86% under pH conditions that are suboptimal for XI activity. These initial findings, which can be optimized for industrial conditions, have significant potential for increasing the yield of ethanol from xylose in an SIF approach.

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Polyacrylamide‐based semi‐interpenetrating networks for entrapment of laccase and their use in azo dye decolorization

Koklukaya

Sezer

Aksoy

et al. 2016

Biotech and App Biochem

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In this study, laccase from Trametes versicolor was immobilized in poly(acrylamide-crotonic acid)/sodium alginate [P(AAm-CrA)/alginate], poly(acrylamide-crotonic acid)/K-carrageenan [(P(AAm-CrA)/K-car)], poly(acrylamide-citraconic acid)/sodium alginate (P(AAm-CA)/alginate), and poly(acrylamide-citraconic acid)/K-carrageenan (P(AAm-CA)/K-car) semi-interpenetrating network by entrapment method. Optimum pH and temperatures values were determined between 5.0-6.0 and 40-50 °C for free laccase (FL) and immobilized laccases, respectively. After 42 days of storage at 4 °C, FL and immobilized laccases retained their original activities in the range of 55%-73%. Percent decolorization of Acid Orange 52 by free enyzme and enyzmes immobilized in hydrogels was found between 63% and 39%. Percent decolorization of Acid Orange 52 in the presence of mediator by free enyzme was found 73% and enyzmes immobilized in hydrogels were found as 73%.

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Demonstration of pH control in a commercial immobilized glucose isomerase

Cited by 11 publications

References 10 publications

A mathematical model for the generation and control of a pH gradient in an immobilized enzyme system involving acid generation

A mathematical model for the generation and control of a pH gradient in an immobilized enzyme system involving acid generation

A Novel Technique that Enables Efficient Conduct of Simultaneous Isomerization and Fermentation (SIF) of Xylose

Polyacrylamide‐based semi‐interpenetrating networks for entrapment of laccase and their use in azo dye decolorization

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