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 particularwith 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.