M. Norsker et al., Enzymatic degradation of plant cell wall polysaccharides: The kinetic effect of competitive adsorption, NAHRUNG, 43(5), 1999, pp. 307-310
Insoluble potato dietary fibre, isolated from potato pulp, can be enzymatic
ally hydrolysed with the pectolytic enzyme preparation Pectinex Ultra SP(R)
from Novo Nordisk A/S, in order to produce soluble fibre. The soluble fibr
e has valuable functional properties for the food industry. Cloned monocomp
onent enzymes from Pectinex Ultra SP(R) (arabinofuranosidase, endoglucanase
II, pectin lyase, polygalacturonase I, rhamnogalacturonan acetyl esterase,
rhamnogalacturonase a, rhamnogalacturonase b and xylanase I) were added in
order to increase the yield. Surprisingly, however, the yield is not incre
ased when any of the monocomponent enzymes are added. To describe the resul
ts a new model designated 'the competitive activity adsorption model' is pr
oposed. The model is based on the fact that the enzymes are adsorbed to the
substrate before action. A combination of the Langmuir adsorption isotherm
and basic enzyme kinetics shows that different enzymes that adsorb competi
tively will have an inhibitory effect on each other and consequently decrea
se the hydrolysis rate and thereby the yield. The model has been confirmed
by an experiment in which the fibre has been pre-treated with rhamnogalactu
ronan acetyl esterase.