Adsorption Kinetics and Behaviour of Two Cellobiohydrolases from Trichoderma Reesei on Microcrystalline Cellulose

Abstract

In order to investigate the adsorption behaviour of cellobiohydrolase I in combination with cellobiohydrolase II (CBH I and CBH II) purified from Trichoderma reesei cellulase on Avicel 101, CBH I and II and their various compositions were adsorbed at 5–35 C. All adsorptions were found to apparently obey the Langmuir isotherm, and the thermodynamic parameters, DHa, DSa and DGa were calculated from the adsorption equilibrium constant, Kad. CBH I had a higher adsorption affinity (Kad) and tightness (‐DHa) for Avicel than CBH II. This indicates that CBH I showed stronger preferential adsorption than CBH II. The reconstituted CBH I and II mixture showed maximum affinity and tightness at a weight ratio of 1:4. The CBH I and II mixture displayed a significant synergistic degradation of Avicel, with a maximum found at a proportion of CBH I and II of 1:4. The increase of affinity (Kad) and tightness (‐ DHa) for the adsorption of CBH I combined with CBH II goes in parallel with their maximum synergistic degradation. It indicates that tightness and affinity of adsorption play a crucial role in synergistic degradation of the microcrystalline cellulose. At a specific weight ratio of CBH I and II, the maximum affinity and tightness of these components existed, and the degree of synergism was maximized at this condition. The synergism of two CBHs can be explained by assuming the formation of a partial complex of CBH I and II, which has higher adsorption affinity and tightness than the individual components, and different specificity in the cellulose attack at a specific optimum ratio of CBHs.

Microbial Cellulose Utilization: Fundamentals and Biotechnology

“…The equilibrium assumption is often justified by the observation that the time required for adsorbed cellulase to reach a constant value is short relative to the time required for hydrolysis. Most studies find that adsorbed cellulase reaches a constant value in Յ90 mins, and many studies have found Յ30 min to be sufficient (74,105,332,333,334,373,508,548,625,651,652), whereas complete hydrolysis of cellulose usually requires a day or more. The simplest representation of adsorption equilibrium is via an equilibrium constant, K d : …”

Access of cellulase to cellulose and lignin for poplar solids produced by leading pretreatment technologies

“…By fitting the adsorption data to the Langmuir equation, adsorption capacities (σ), equilibrium constants ( K d ), affinity constants (1/ K d ), and strength of binding ( R = σ × affinity constant) were estimated, as shown in Table 4. The affinity of cellulase to poplar solids was determined by the Gibb's free energy equation as well, ΔGa = − R × T × ln( K d ),74 where the larger negative values of free energy indicate more spontaneous cellulase adsorption on solids. However, although the glucan content in the pretreated poplar solids from all pretreatments was only about 50%, all but those from controlled pH pretreatment showed higher adsorption capacity than the nearly pure glucan in Avicel.…”

“…Solids produced by FT and dilute acid pretreatment had a higher cellulase adsorption capacity (195 mg/g glucan and 170 mg/g glucan, respectively) than other pretreatments. The affinity or strength of cellulase binding to solids, which is often considered vital among enzyme factors controlling hydrolysis,71, 74, 99 was also very high for SO 2 and dilute acid pretreated solids followed by that for pure Avicel glucan. However, although it is difficult to ascertain a single factor impacting glucan hydrolysis results, the normalized effectiveness of cellulase to Avicel for these two pretreatments was found to be higher than for other pretreatments, as shown in Figure 7.…”

Kinetic modeling of cellulosic biomass to ethanol via simultaneous saccharification and fermentation: Part II. Experimental validation using waste paper sludge and anticipation of CFD analysis

“…The two substrates have about the same conversion after 5 days with the same cellulase loading due to compensatory differences in the values for the rate constant, adsorption capacity, and reaction exponent. Prior efforts to model cellulase adsorption known to us have been based on data taken with fractional cellulose conversion at or near zero (Bothwell et al, 1997;Kim et al, 1998;Kim and Hong, 2000;Nidetzky and Claeyssens, 1994;Ooshima et al, 1990;Tomme et al, 1995). In this study, cellulose conversion was incorporated into the adsorption model and parameters were fit to data taken over a range of conversions from near zero to 65%.…”