Hydrolytic enzymes thermal stability

Thermal stability of soluble or immobilized enzyme was determined by incubating the biocatalyst in 100 mM sodium phosphate buffer pH 7.0 at 50 or 60 °C. Periodically, samples were withdrawn, and their residual activities were assayed by the hydrolysis of methyl butyrate. Residual activity is given as percentage of initial activity (hydrolytic activity before incubation). Thermal deactivation curves have been described following the... 

In the present work, green coconut fiber was successfiilly used to immobilize lipase B from C. antarctica by adsorption. During adsorption studies, it was observed that adsorption equilibrium was achieved afler a contact time of 2 h (in case of o=30 U/ml and Eo=(0 U/ml) or 6 h ( o=90 U/ml). Moreover, an improvement of hydrolytic activity of immobilized CALB is also observed with increasing concentrations of lipase offered to immobilization. This increase in activity is due to formation of multilayers, confirmed by thermal stability essays. Two plateaus of enzyme activity were observed when the pH of lipase solution during adsorption was varied in the range studied. This behavior is typical of an ionic support At 50 and 60 °C, the adsorbed enzyme was, respectively, 2- and 92-fold more stable than the soluble enzyme. At 60 °C, however, Novozyme 435 s stability was higher than that of CALB-7A. TUIer 10 h of incubation at 60 °C, Novozyme 435 retained more than 70% of its initial activity, whereas CALB-7A retained only 50%. Last but not least operational stabilities studies of butyl butyrate synthesis, compared to a commercial derivative, showed that C7U..B-7A is a suitable biocatalyst to be used in the synthesis of flavors. 

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