Application of ß-glucuronidase-immobilised silica gel formulation to microfluidic platform for biotransformation of ß-glucuronides.

OBJECTIVE: To improve the efficiency of reactions of ß-glucuronidase (GUS)-assisted glucuronic acid (GluA) removal within a microfluidic system. RESULTS: ß-glucuronidase from Helix pomatia was immobilised and characterised in silica-based sol-gel monoliths. Efficiency of the GUS-doped silica monoliths was tested for hydrolysis of p-Nitrophenyl-ß-D-glucuronide (pNP-GluA) in both ml-scaled medium via batch reactions and microfluidic environment via continuous-flow reactions. In the microfluidic platform, within a duration of 150 min of continuous operation (flow rate: 1 µL/min), the obtained highest pNP yield was almost 50% higher than that of the corresponding batchwise reaction. However, increased flow rates (3, 5, and 10 µL/min) resulted in lower conversion yields compared to 1 µL/min. The microfluidic platform demonstrated continuous hydrolytic activity for 7 days with considerable reaction yields while using a small amount of the enzyme. CONCLUSION: These results revealed that usage of the microreactors has considerable potential to efficiently obtain bioactive GluA-free aglycons from various plant-derived ß-glucuronides for pharmaceutical applications.

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

The aim of this study was to formulate silica and alginate hydrogels for immobilization of ß-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 ß-glucosidase was loaded into glass-silicon-glass microreactors and catalysis of 4-nitrophenyl ß-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.