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Development of a fully integrated falling film microreactor for gas–liquid–solid biotransformation with surface immobilized O 2 ‐dependent enzyme
Author(s) -
Bolivar Juan M.,
Krämer Christina E. M.,
Ungerböck Birgit,
Mayr Torsten,
Nidetzky Bernd
Publication year - 2016
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.25969
Subject(s) - microreactor , microchannel , mass transfer , chemistry , immobilized enzyme , laminar flow , analytical chemistry (journal) , mass transfer coefficient , chromatography , countercurrent exchange , volumetric flow rate , chemical engineering , catalysis , materials science , nanotechnology , thermodynamics , organic chemistry , enzyme , physics , engineering
Microstructured flow reactors are powerful tools for the development of multiphase biocatalytic transformations. To expand their current application also to O 2 ‐dependent enzymatic conversions, we have implemented a fully integrated falling film microreactor that provides controllable countercurrent gas–liquid phase contacting in a multi‐channel microstructured reaction plate. Advanced non‐invasive optical sensing is applied to measure liquid‐phase oxygen concentrations in both in‐ and out‐flow as well as directly in the microchannels (width: 600 μm; depth: 200 μm). Protein–surface interactions are designed for direct immobilization of catalyst on microchannel walls. Target enzyme (here: d ‐amino acid oxidase) is fused to the positively charged mini‐protein Z basic2 and the channel surface contains a negatively charged γ‐Al 2 O 3 wash‐coat layer. Non‐covalent wall attachment of the chimeric Z basic2 _oxidase resulted in fully reversible enzyme immobilization with fairly uniform surface coverage and near complete retention of biological activity. The falling film at different gas and liquid flow rates as well as reactor inclination angles was shown to be mostly wavy laminar. The calculated film thickness was in the range 0.5–1.3 × 10 −4 m. Direct O 2 concentration measurements at the channel surface demonstrated that the liquid side mass transfer coefficient ( K L ) for O 2 governed the overall gas/liquid/solid mass transfer and that the O 2 transfer rate (≥0.75 mM · s −1 ) vastly exceeded the maximum enzymatic reaction rate in a wide range of conditions. A value of 7.5 (±0.5) s −1 was determined for the overall mass transfer coefficient K L a , comprising a K L of about 7 × 10 −5 m · s −1 and a specific surface area of up to 10 5 m −1 . Biotechnol. Bioeng. 2016;113: 1862–1872. © 2016 Wiley Periodicals, Inc.