Exploration of a three-dimensional matrix as micro-reactor in the form of reactive polyaminosaccharide hydrogel beads...

Diversity in backbone polymer composition makes hydrogel-based resources open to broad spectrum of applications. Biomacromolecules which have reactive functional groups in their structural frame and can also exhibit hydrogel properties could be utilized in biomedical, pharmaceutical and drug delivery applications after some chemical modifications.

Present study aims towards development of chitosan-based hydrogel system crosslinked together with glucosyltransferase. Hydrogel structure worked as an immobilization matrix and as a microreactor system to catalyze the cleavage of a disaccharide. Uniform chitosan hydrogel beads were prepared and dextransucrase was attached using multipoint covalent interaction approach. Strong interaction was developed by linking polymeric hydrogel with the biocatalyst utilizing glutaraldehyde as spacer arms. This bifunctional crosslinking agent performed two important tasks that includes functionalization of hydrogel beads and crosslinking of this activated matrix system with enzyme fragments. Hydrogel beads required 18.0 h crosslinking time with enzyme (6.5 mg ml^-1, 189.9 DSU) under specific environment (4 °C, 100 rpm) to saturate all available ends. Enzyme fragments were observed bound with hydrogel beads when screened for surface topology indicating successful crosslinking. Steady state kinetics of crosslinked dextransucrase was studied in detail and it was revealed that it can catalyse sucrose in 30.0 min at 35 °C (pH 5.5) with an energy of activation around 15.23 kJ mol^-1 with increased V_max (785 DSU ml^-1) and K_m (256 mM) values as compared to soluble enzyme version. Thermal stability of the crosslinked dextransucrase also particularly improved 2.5 fold at 45 °C in comparison with soluble enzyme. Improved catalytic performance suggests that multipoint covalent immobilization protocol adapted using hydrogel system could be tailored as microreactor for catalysis of profitable macromolecules.