Enzymatic degradation of plant cell wall polysaccharides: The kinetic effect of competitive adsorption

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.