Simple Protocol to Facilitate Students’ Understanding of the Effects of Enzyme Immobilization on Kinetics of Reaction and Mass Transfer

A laboratory experiment is described in which students carry out immobilization of the enzyme invertase via entrapment in alginate (Ca-alginate) and, accordingly, estimate values for kinetic constants and mass transfer coefficients. Immobilization of enzymes, or confinement thereof to a defined space with retention of most catalytic activity, is attractive for allowing repeated (and continuous) use. However, interest in immobilization hinges critically on whether and how it affects kinetic performance. The overall goal is indeed to retain as much activity as possible and minimize alteration of selectivity, while extending its useful life for as long as feasible. Toward this goal, it is relevant to quantify the effects of immobilization upon enzyme kinetics and mass transfer in particular—with the latter constraining observed (rather than intrinsic) reaction kinetics, owing to diffusional resistance. Invertase was selected as a model enzyme since the associated laboratory handling is safe, fast, reproducible, not expensive, and prone to easily attain the intended learning outcomes.