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

Abstract

Insoluble potato dietary fibre, isolated from potato pulp, can be enzymatically hydrolysed with the pectolytic enzyme preparation Pectinex Ultra SP from Novo Nordisk A/S, in order to produce soluble fibre. The soluble fibre has valuable functional properties for the food industry. Cloned monocomponent enzymes from Pectinex Ultra SP (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 increased when any of the monocomponent enzymes are added. To describe the results a new model designated 'the competitive activity adsorption model' is proposed. 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 competitively will have an inhibitory effect on each other and consequently decrease the hydrolysis rate and thereby the yield. The model has been confirmed by an experiment in which the fibre has been pre-treated with rhamnogalacturonan acetyl esterase.

Enriching and characterizing an aerotolerant mixed microbial community capable of cellulose hydrolysis and ethanol production

“…Cellobiohydrolases remove cellobiose molecules from the ends of cellodextrins, while β-glycosidases liberate glucose monomers from cellobiose (Lynd et al, 2002). Interestingly, Norsker et al (1999) have…”

“…This group observed that in a stable cellulose-degrading mixed community, each cellulolytic member possesses a slightly different set of cellulases, which together are expressed in a fine balance. Thus, slight fluctuations in the ratio of the expressed cellulases can diminish the overall cellulose-degrading activity of the community (Norsker et al, 1999).…”

“…Anaerobic bacteria have evolved to utilize the cellulosome because it offers several advantages over the use of cell-free enzymes. It allows the cell to directly control the ratio of enzymatic subunits being expressed (Schwarz, 2001), which has been shown to affect the rate of hydrolysis (Norsker et al, 1999). Also, since the cellulosome facilitates direct contact between the cell and the cellulosic substrate, the distance hydrolysis products must travel to be taken up and metabolized by the cell is significantly reduced (Lynd et al, 2002;Wang and Chen, 2009).…”

Interaction between clostridium thermocellum ATCC 27405 and thermoanaerobacterium saccharolyticum DSM 7060 on cellulosic and lignocellulosic substrates: substrate attachment, concentration dynamics, and ethanol production

“…Anaerobic cellulolytic bacteria have evolved to use cellulosomes due to their advantages over cell-free enzymes. The cellulosome allows the cell to directly regulate and control the ratio of expression of enzymatic subunits, which directly affects the rate of hydrolysis (Norsker et al, 1999). In addition, the physical distance between the cell and the cellulose substrate is subsequently reduced (Lynd et al, 2002).…”

Enzymatic hydrolysis and extraction of arachidonic acid rich lipids from Mortierella alpina

“…It is possible that the two enzymes competitively absorb on the substrates and demonstrate an inhibitory effect on each other, thereby resulting in lower yields. Norsker et al (1999) have recently confirmed such effects. The yield of oil from the mixtures of showing synergistic action (R.S.D.…”