A Simple Individual-based Model of Insoluble Polysaccharide Hydrolysis: the Potential for Autosynergism with Dual-activity Glycosidases

A functionally based model for hydrolysis of cellulose by fungal cellulase

“…Among such phenomena are effects of high enzyme loading, including competitive or synergistic adsorption of cellulase components (Jeoh et al, 2002;Kyriacou et al, 1989;Ryu et al, 1984), as well as implications of incorporating a substrate material balance distinguishing between free and total substrate sites (Lynd et al, 2002). Further phenomena relevant in this context include changes in F a and perhaps other substrate properties during the course of hydrolysis (Ooshima et al, 1990;Valjamae et al, 1998;Zhang et al, 1999), as well as product inhibition (Gong et al, 1977;Holtzapple et al, 1990;Hong et al, 1981;Ladisch et al, 1980Ladisch et al, , 1981, substrate inhibition (Fenske et al, 1999;Hong et al, 1981;Huang and Penner, 1991;Valjamae et al, 2001), and cellulase deactivation and/or unproductive binding (Kadam et al, 2004;Valjamae et al, 2001). A model that meaningfully incorporates random adsorption, active-and inactive-adsorbed species, and dependence upon the availability of chain ends is an important objective for future research.…”

“…Converse and Optekar (1993), using surface area as a substrate state variable, predicted a lower degree of synergism at high cellulase loadings due to competitive adsorption. Fenske et al (1999) used virtual DP and surface area as substrate state variables in addition to concentration to gain insights into inhibition of cellulase activity by insoluble substrates.…”

“…In the case of three of the four functionally based models (Fenske et al, 1999;Okazaki and Moo-Young, 1978;Suga et al, 1975), no comparison to experimental data has been made. Converse and Optekar (1993) compared model results to a single set of experimental data with a focus exclusively on synergism.…”

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems

“…Semimechanistic models with respect to enzyme only (>2 substrate state variables, 1 solubilizing activity) Converse and Grethlein, 1987 AS Peitersen and Ross, 1979 A + C plus BG M-M Fan and A + C plus BG Langmuir uncompetitive Scheiding et al, 1984 A + C plus BG Langmuir non-competitive Guaskov et al, 1985a and b A + C plus BG Langmuir competitive Gonzalez et al, 1989 A + C plus BG M-M competitive Nidetzky et al, 1993 A + C plus BG Langmuir Wald et al, 1984 AS + (A + C) plus BG Langmuir competitive Gan et al, 2003 AS + (A + C) plus BG Langmuir competitive iii. Semi mechanistic models with respect to substrate only (1 substrate state variable and 2 solubilizing activities) Beltrame et al, 1984 only [S] Endo+Exo+BG M-M non-competitive Nidetzky et al, 1994b only [S] Endo+Exo Langmuir C. Functionally based models (z2 substrate state variables, z2 solubilizing activities) Suga et al, 1975 [S], DP Endo+Exo M-M Okazaki and Moo-Young, 1978 [S], DP Endo+Exo M-M non-competitive Converse and Optekar, 1993 [S], AS Endo+Exo Dynamic adsorption Fenske et al, 1999 [S], AS, DP Endo+Exo Langmuir *AS = surface area; [S], substrate concentration; X = cellulose conversion; A, amorphous cellulose; C, crystalline cellulose.…”

“…Converse and Optekar (1993) considered competitive adsorption of exoglucanase and endoglucanase for a limited number of sites, and predicted a lower DS under oversaturating conditionsthat is, when cellulase is in substantial excess relative to the substrate. Fenske et al (1999) modeled and observed a decline in hydrolysis rate with increasing cellulose concentration (Huang and Penner, 1991;Valjamae et al, 2001) in terms of decreased synergism when cellulase components with complementary activities bind at a distance from each other.…”