The adsorption of α-chymotrypsin onto plant biomass charcoal (PBC), which was prepared from plant biomass wastes such as bagasse and dumped adzuki beans by pyrolysis, has been examined. The PBC was characterized by SEM, specific surface area, and pore size distribution. The adsorption isotherms were successfully correlated by the Freundlich equation. The amount of α-chymotrypsin adsorbed on PBC was dramatically dependent upon the solution pH and temperature. Maximum adsorptions of α-chymotrypsin on adzuki bean charcoal and bagasse charcoal were observed at weak acidic and near neutral pH, respectively. The amount of α-chymotrypsin adsorbed on PBC decreased with an increase in the concentration of salts. Plots of the amount of α-chymotrypsin adsorbed on PBC versus temperature exhibited an optimum temperature.
We have found that the organic solvent-resistance of α-chymotrypsin (α-CT) is enhanced by adsorbing α-CT onto bamboo charcoal powder (BCP), which is obtained by pyrolyzing bamboo waste under nitrogen atmosphere, and is markedly dependent on the thermodynamic water activity (a w ) in organic solvents. When BCP-adsorbed α-CT was immersed in acetonitrile at an appropriate water activity, it effectively enhanced the transesterification of Nacetyl-L-tyrosine ethyl ester (N-Ac-Tyr-OEt) with n-butanol (BuOH) to produce N-acetyl-L-tyrosine butyl ester (N-Ac-Tyr-OBu), compared to the hydrolysis of N-Ac-Tyr-OEt with water to give N-acetyl-L-tyrosine (N-Ac-Tyr-OH). When the water activity was 0.28, the initial rate of transesterification catalyzed by BCP-adsorbed α-CT was about sixty times greater than that catalyzed by free α-CT. Regarding the reaction selectivity which is defined as a ratio of the initial rate of transesterification to that of hydrolysis, BCP-adsorbed α-CT was much superior to free α-CT. The catalytic activity of BCP-adsorbed α-CT was markedly dependent on the reaction temperature. Furthermore, concerning the thermal stability at 50 ℃, the half-life of BCP-adsorbed α-CT exhibited 3.8-fold, compared to that of free α-CT.
We have found that the adsorption immobilization of the serine protease α-chymotrypsin (Alpha-CT) onto bamboo charcoal powder (BCP), which is a kind of biochar, improves the transesterification rate of N-acetyl-L-tyrosine ethyl ester (N-Ac-Tyr-OEt) with n-butanol (BuOH) in 9 organic solvents. Organic solvents strongly affected the catalysis of BCP-adsorbed Alpha-CT. The transesterification rate of BCP-adsorbed Alpha-CT was much superior to that of free Alpha-CT in every organic solvent. Especially, the transesterification rate of BCP-adsorbed Alpha-CT was about 760 times higher than that of free α-CT in n-butyl acetate.
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