title: Real-time pH monitoring of industrially relevant enzymatic reactions in a microfluidic side-entry reactor (μSER) shows potential for pH control.
abstract: Monitoring and control of pH is essential for the control of reaction conditions and reaction progress for any biocatalytic or biotechnological process. Microfluidic enzymatic reactors are increasingly proposed for process development, however typically lack instrumentation, such as pH monitoring. We present a microfluidic side-entry reactor (μSER) and demonstrate for the first time real-time pH monitoring of the progression of an enzymatic reaction in a microfluidic reactor as a first step towards achieving pH control. Two different types of optical pH sensors were integrated at several positions in the reactor channel which enabled pH monitoring between pH 3.5 and pH 8.5, thus a broader range than typically reported. The sensors withstood the thermal bonding temperatures typical of microfluidic device fabrication. Additionally, fluidic inputs along the reaction channel were implemented to adjust the pH of the reaction. Time-course profiles of pH were recorded for a transketolase and a penicillin G acylase catalyzed reaction. Without pH adjustment, the former showed a pH increase of 1 pH unit and the latter a pH decrease of about 2.5 pH units. With pH adjustment, the pH drop of the penicillin G acylase catalyzed reaction was significantly attenuated, the reaction condition kept at a pH suitable for the operation of the enzyme, and the product yield increased. This contribution represents a further step towards fully instrumented and controlled microfluidic reactors for biocatalytic process development.
authors.affiliation: Department of Biochemical Engineering, University College London, Gordon Street, London, UK.
authors.forename: Pia
authors.initials: P
authors.lastname: Gruber
authors.affiliation: Department of Biochemical Engineering, University College London, Gordon Street, London, UK.
authors.forename: Marco P C
authors.initials: MPC
authors.lastname: Marques
authors.affiliation: Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Graz, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Sulzer
authors.affiliation: Member of Merck Group, Sigma-Aldrich, Member of Merck Group, Buchs, Switzerland.
authors.forename: Roland
authors.initials: R
authors.lastname: Wohlgemuth
authors.affiliation: Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Graz, Austria.
authors.forename: Torsten
authors.initials: T
authors.lastname: Mayr
authors.affiliation: Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Graz, Austria.
authors.forename: Frank
authors.initials: F
authors.lastname: Baganz
authors.affiliation: Department of Biochemical Engineering, University College London, Gordon Street, London, UK.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Szita
mesh_terms: D055162:Biocatalysis; D019149:Bioreactors; D002384:Catalysis; D057075:Enzyme Assays; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D056656:Lab-On-A-Chip Devices; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D044085:Microfluidics; D014174:Transketolase / Q000378:metabolism
chemical_list: D014174:Transketolase
keywords: Microreactor; Online monitoring; Optical sensor; Penicillin G acylase; Transketolase; pH sensor