Rene Heils

An injectable alginate-based hydrogel for microfluidic applications

The objective of this study was to develop an injectable alginate based formulation for immobilizing enzymes into microfluidic systems. The gelation was induced upon lowering the pH by addition of d-glucono-δ-lactone (GDL) and release of Ca+ ions from solid CaCO3. The effects of GDL concentration on enzymatic activity and gelation time were investigated. The results indicated that increasing the GDL concentration increased both surface area and enzymatic activity. Also, chitosan was added to the formulation at different ratios to enhance the stability of enzyme during immobilization. For microfluidic application, 100μl spiral coil single channel microchip was fabricated and alginate GDL mixture containing β-glucosidase was injected to the microchannel prior to gelation. Enzymatic conversion was performed by pumping substrate (pNPG) through the microchannel. The results indicated that the entire substrate was converted continuously during 24h without any leakage or deactivation of immobilized enzyme.

Formulation of organic and inorganic hydrogel matrices for immobilization of β-glucosidase in microfluidic platform

The aim of this study was to formulate silica and alginate hydrogels for immobilization of β‐glucosidase. For this purpose, enzyme kinetics in hydrogels were determined, activity of immobilized enzymes was compared with that of free enzyme, and structures of silica and alginate hydrogels were characterized in terms of surface area and pore size. The addition of polyethylene oxide improved the mechanical strength of the silica gels and 68% of the initial activity of the enzyme was preserved after immobilizing into tetraethyl orthosilicate–polyethylene oxide matrix where the relative activity in alginate beads was 87%. The immobilized β‐glucosidase was loaded into glass–silicon–glass microreactors and catalysis of 4‐nitrophenyl β‐d‐glucopyranoside was carried out at various retention times (5, 10, and 15 min) to compare the performance of silica and alginate hydrogels as immobilization matrices. The results indicated that alginate hydrogels exhibited slightly better properties than silica, which can be utilized for biocatalysis in microfluidic platforms.

CHAPTER 10:Enzymatic Reactive Absorption and Distillation

In this work, innovative concepts for reactive separation processes, such as reactive absorption and distillation, that make use of bio-based catalysts, in specific enzymes, are discussed. Enzymatic Reactive Absorption (ERA) and Distillation (ERD) offer potential for energy and investment savings or improved selectivity by exploiting enzyme merits like high enantioselectivity and high reaction rates at milder reaction conditions than chemical catalysts. Potential process equipment, application strategies to supply enzyme for ERA and ERD processes as well as suitable modeling and design approaches are presented. Despite the huge potential, addressing these issues is crucial in order to promote ERA and ERD as vital technologies for process intensification in bio-based industries. The application of the enzyme carbonic anhydrase in an ERA column with common MDEA-based solvent can drastically improve the absorption of CO2 by more than 9-fold. Furthermore, the production of butyl butyrate and enantiomerically pure (R)-1-phenylethyl acetate or (S)-2-pentanol were successfully demonstrated in an ERD column. These processes provided high conversion rates of the substrates and purities of the product stream at milder process conditions compared to conventional processes.