Young Kyu Jeong

Adsorption kinetics and behaviors of cellulase components on microcrystalline cellulose

Abstract In order to investigate the interactive adsorption behaviors between each cellulase component purified from Trichoderma viride cellulase on microcrystalline cellulose, the adsorption of CMCase, Avicelase, and various compositions of CMCase and Avicelase was performed at 25–45°C. All adsorptions were found to apparently obey the Langmuir isotherm and the thermodynamic parameters, ΔHa, ΔSa, and ΔGa were calculated from the adsorption equilibrium constant, Kad. The adsorption process was found to be endothermic and an adsorption entropy-controlled reaction. The amount of adsorption of cellulase components decreased with increasing temperature and varied with a change in composition of the cellulase components. The maximum synergistic degradation occurred at the specific mass ratio of the cellulase components at which the maximum affinity of cellulase components occurred.

Purification and characterization of endoglucanase and exoglucanase components from Trichoderma viride

Major cellulase components—four endoglucanases (Endo I, II, III and IV) and one exoglucanase (Exo II)—were isolated from a commercial cellulase preparation derived from Trichoderma viride by a series of chromatographic procedures. The average molecular weights were determined by SDS-polyacrylamide gel electrophoresis. Endos I, III and IV, with Mrs of 52,000, 42,000 and 38,000, respectively, exhibited a more random hydrolytic mode on carboxymethylcellulose (CMC) than Endo II, which has an Mr of 60,000. Endo II showed low activity towards CMC, but out of the four purified endoglucanases this enzyme had the highest specific activity against Avicel. In the hydrolysis of H3PO4-swollen cellulose by Endos I, III and IV, cellobiose was the major product, but equimolar amounts of glucose and cellobiose were formed by Endo II. Exo II, with an Mr of 62,000, released cellobiose as the main product in the hydrolysis of H3PO4-swollen cellulose, but glucose was negligible. The combination of Endo I, II, III or IV with Exo II resulted in a synergistic effect in the degradation of Avicel at various combination ratios of these enzymes; the specific optimum ratio of endoglucanase to exoglucanase was largely dependent upon the random hydrolytic mode of the endoglucanase. On the other hand, adsorption of cellulase components was found apparently to obey the Langmuir isotherm, and the thermodynamic parameter (ΔH) was calculated from the adsorption equilibrium constant (K). The enthalpies of adsorption of the endoglucanases were in the range of −2.6–−7.2 KJmol−1, much smaller than that of Exo II (−19.4 KJmol−1). This suggest that Exo II shows stronger preferential adsorption than endoglucanases, and that the enthalpy of adsorption will be effective in distinguishing endoglucanase from exoglucanase.

Adsorption kinetics of exoglucanase in combination with endoglucanase from Trichoderma viride on microcrystalline cellulose and its influence on synergistic degradation

Abstract In order to investigate the adsorption behaviors of endoglucanases (Endo I, II, III, and IV) in combination with exoglucanase (Exo II) purified from Trichoderma viride cellulase on microcrystalline cellulose, the adsorption of Endo I, II, III, and IV, Exo II and their various compositions was performed at 15–35°C. All adsorptions were found to apparently obey the Langmuir isotherm, and the thermodynamic parameters ΔHa, ΔSa, and ΔGa were calculated from the adsorption equilibrium constant, K ad . The adsorption process was found to be exothermic and an adsorption enthalpy-controlled reaction. The values of enthalpy of adsorption of the reconstituted enzyme mixtures on cellulose were ranged about −9 ∼ −21 KJ mol −1 , and the interaction responsible for adsorption is regarded as arising as a result of specific van der Waals-type interactions. Equilibrium constant ( K ad ) and maximum adsorption amount ( A max ) values varied with a change in composition of the cellulase components. The optimum ratio of adsorbed endoglucanase and exoglucanase depended largely upon the degree of randomness of endoglucanase. And the maximal synergistic degradation occurred at a specific optimal ratio of adsorbed endoglucanase and exoglucanase. From the relationships between the degree of synergistic degradation and thermodynamic parameters (ΔHa and ΔGa), it was found that the ability of cellulase components to solubilize microcrystalline cellulose is directly correlated with tightness (ΔHa) and affinity (ΔGa) to be adsorbed on it.

Lithium isotope separation by chemical exchange with polymer-bound azacrown compounds

The chromatographic separation of lithium isotopes was investigated by chemical exchange with the recently synthesized polymer-bound dibenzo pyridino diamide azacrown (DBPDA) and reduced dibenzo pyridino diamide azacrown (RDBPDA). Column chromatography was employed for the determination of the effect of solvents and ligand conformation on the separation coefficients. The maximum separation coefficients, ε, for the DBPDA and RDBPDA at 20.0±0.02°C with acetonitrile as eluent, were found to be 0.034±0.002 and 0.035±0.002, respectively. The isotope separation coefficient and adsorption capability of the lithium ion on the DBPDA and RDBPDA were only slightly dependent on ligand structure, but strongly dependent on the solvent. DBPDA and RDBPDA appeared to have almost the same value for the isotope separation coefficient of lithium.