Let the substrate flow, not the enzyme: Practical immobilization of d-amino acid oxidase in a glass microreactor for effective biocatalytic conversions

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Abstract

Exploiting enzymes for chemical synthesis in flow microreactors necessitates their reuse for multiple rounds of conversion. To achieve this goal, immobilizing the enzymes on microchannel walls is a promising approach, but practical methods for it are lacking. Using fusion to a silica-binding module to engineer enzyme adsorption to glass surfaces, we show convenient immobilization of d-amino acid oxidase on borosilicate microchannel plates. In confocal laser scanning microscopy, channel walls appeared uniformly coated with target protein. The immobilized enzyme activity was in the range expected for monolayer coverage of the plain surface with oxidase (2.37 × 10−5 nmol/mm2). Surface attachment of the enzyme was completely stable under flow. The operational half-life of the immobilized oxidase (25°C, pH 8.0; soluble catalase added) was 40 h. Enzymatic oxidation of d-Met into α-keto-γ-(methylthio)butyric acid was characterized in single-pass and recycle reactor configurations, employing in-line measurement of dissolved O2, and off-line determination of the keto-acid product. Reaction-diffusion time-scale analysis for different flow conditions showed that the heterogeneously catalyzed reaction was always slower than diffusion of O2 to the solid surface (DaII ≤ 0.3). Potential of the microreactor for intensifying O2-dependent biotransformations restricted by mass transfer in conventional reactors is thus revealed. Biotechnol. Bioeng. 2016;113: 2342–2349.

LanguageEnglish
Pages2342-2349
Number of pages8
JournalBiotechnology and Bioengineering
Volume113
Issue number11
DOIs
StatusPublished - 1 Nov 2016

Fingerprint

Enzyme immobilization
Immobilization
Glass
Amino acids
Oxidoreductases
Enzymes
Amino Acids
Substrates
Microchannels
Keto Acids
Immobilized Enzymes
Butyric acid
Butyric Acid
Enzyme activity
Biotransformation
Confocal Microscopy
Silicon Dioxide
Catalase
Adsorption
Half-Life

Keywords

  • enzymatic oxidation
  • flow microreactor
  • glass
  • immobilization
  • microfluidics
  • silica-binding module

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

Cite this

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abstract = "Exploiting enzymes for chemical synthesis in flow microreactors necessitates their reuse for multiple rounds of conversion. To achieve this goal, immobilizing the enzymes on microchannel walls is a promising approach, but practical methods for it are lacking. Using fusion to a silica-binding module to engineer enzyme adsorption to glass surfaces, we show convenient immobilization of d-amino acid oxidase on borosilicate microchannel plates. In confocal laser scanning microscopy, channel walls appeared uniformly coated with target protein. The immobilized enzyme activity was in the range expected for monolayer coverage of the plain surface with oxidase (2.37 × 10−5 nmol/mm2). Surface attachment of the enzyme was completely stable under flow. The operational half-life of the immobilized oxidase (25°C, pH 8.0; soluble catalase added) was 40 h. Enzymatic oxidation of d-Met into α-keto-γ-(methylthio)butyric acid was characterized in single-pass and recycle reactor configurations, employing in-line measurement of dissolved O2, and off-line determination of the keto-acid product. Reaction-diffusion time-scale analysis for different flow conditions showed that the heterogeneously catalyzed reaction was always slower than diffusion of O2 to the solid surface (DaII ≤ 0.3). Potential of the microreactor for intensifying O2-dependent biotransformations restricted by mass transfer in conventional reactors is thus revealed. Biotechnol. Bioeng. 2016;113: 2342–2349.",
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AU - Bolivar Bolivar,Juan Manuel

AU - Tribulato,Marco Antonino

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AB - Exploiting enzymes for chemical synthesis in flow microreactors necessitates their reuse for multiple rounds of conversion. To achieve this goal, immobilizing the enzymes on microchannel walls is a promising approach, but practical methods for it are lacking. Using fusion to a silica-binding module to engineer enzyme adsorption to glass surfaces, we show convenient immobilization of d-amino acid oxidase on borosilicate microchannel plates. In confocal laser scanning microscopy, channel walls appeared uniformly coated with target protein. The immobilized enzyme activity was in the range expected for monolayer coverage of the plain surface with oxidase (2.37 × 10−5 nmol/mm2). Surface attachment of the enzyme was completely stable under flow. The operational half-life of the immobilized oxidase (25°C, pH 8.0; soluble catalase added) was 40 h. Enzymatic oxidation of d-Met into α-keto-γ-(methylthio)butyric acid was characterized in single-pass and recycle reactor configurations, employing in-line measurement of dissolved O2, and off-line determination of the keto-acid product. Reaction-diffusion time-scale analysis for different flow conditions showed that the heterogeneously catalyzed reaction was always slower than diffusion of O2 to the solid surface (DaII ≤ 0.3). Potential of the microreactor for intensifying O2-dependent biotransformations restricted by mass transfer in conventional reactors is thus revealed. Biotechnol. Bioeng. 2016;113: 2342–2349.

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