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Review

The Microenvironment in Immobilized Enzymes: Methods of Characterization and Its Role in Determining Enzyme Performance

by 1,2,* and 1,3,*
1
Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12, A-8010 Graz, Austria
2
Chemical and Materials Engineering Department, Complutense University of Madrid, 28040 Madrid, Spain
3
Austrian Centre of Industrial Biotechnology (acib), Petersgasse 14, A-8010 Graz, Austria
*
Authors to whom correspondence should be addressed.
Academic Editor: Roberto Fernandez-Lafuente
Molecules 2019, 24(19), 3460; https://doi.org/10.3390/molecules24193460
Received: 13 August 2019 / Revised: 17 September 2019 / Accepted: 19 September 2019 / Published: 24 September 2019
(This article belongs to the Special Issue Enzyme Immobilization and Its Applications)
The liquid milieu in which enzymes operate when they are immobilized in solid materials can be quite different from the milieu in bulk solution. Important differences are in the substrate and product concentration but also in pH and ionic strength. The internal milieu for immobilized enzymes is affected by the chemical properties of the solid material and by the interplay of reaction and diffusion. Enzyme performance is influenced by the internal milieu in terms of catalytic rate (“activity”) and stability. Elucidation, through direct measurement of differences in the internal as compared to the bulk milieu is, therefore, fundamentally important in the mechanistic characterization of immobilized enzymes. The deepened understanding thus acquired is critical for the rational development of immobilized enzyme preparations with optimized properties. Herein we review approaches by opto-chemical sensing to determine the internal milieu of enzymes immobilized in porous particles. We describe analytical principles applied to immobilized enzymes and focus on the determination of pH and the O2 concentration. We show measurements of pH and [O2] with spatiotemporal resolution, using in operando analysis for immobilized preparations of industrially important enzymes. The effect of concentration gradients between solid particle and liquid bulk on enzyme performance is made evident and quantified. Besides its use in enzyme characterization, the method can be applied to the development of process control strategies. View Full-Text
Keywords: biocatalysis; immobilization; microenvironment; internal milieu; reaction-diffusion; opto-chemical sensing; pH; oxygen; porous materials biocatalysis; immobilization; microenvironment; internal milieu; reaction-diffusion; opto-chemical sensing; pH; oxygen; porous materials
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MDPI and ACS Style

Bolivar, J.M.; Nidetzky, B. The Microenvironment in Immobilized Enzymes: Methods of Characterization and Its Role in Determining Enzyme Performance. Molecules 2019, 24, 3460. https://doi.org/10.3390/molecules24193460

AMA Style

Bolivar JM, Nidetzky B. The Microenvironment in Immobilized Enzymes: Methods of Characterization and Its Role in Determining Enzyme Performance. Molecules. 2019; 24(19):3460. https://doi.org/10.3390/molecules24193460

Chicago/Turabian Style

Bolivar, Juan M., and Bernd Nidetzky. 2019. "The Microenvironment in Immobilized Enzymes: Methods of Characterization and Its Role in Determining Enzyme Performance" Molecules 24, no. 19: 3460. https://doi.org/10.3390/molecules24193460

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