In this study, flavonoid rutin was acylated with lauric acid in acetone catalyzed by an immobilized lipase from Candida antarctica. In addition to the reaction not being well studied, the esterification also involves two immiscible substrates, which posed a significant challenge. Analysis indicated that the lipase-mediated esterification exhibits a ping-pong bi−bi mechanism with no apparent inhibition by the two substrates. The activation energy, E a , for the esterification was calculated as ∼37 kJ mol −1 . The esterification process was found to be endothermic, with enthalpy (ΔH) and entropy (ΔS) values of approximately +50 kJ mol −1 and +110 J mol −1 K −1 , respectively. Based on the value of the Gibbs free energy change (ΔG), the esterification reaction under the conditions studied was predicted to be nonspontaneous below 175 °C but spontaneous at higher temperatures. The study also confirmed, through 13 C NMR analysis, the exact location of rutin esterification. The investigated esterification biochemistry highlighted important behavior concerning the enzyme-mediated synthesis of functionalized flavonoid.

Free laccase and fungal biomass from white-rot fungi were compared in the thermokinetics study of the laccase-catalyzed decolorization of an azo dye, i.e., Trypan Blue. The decolorization in both systems followed a first-order kinetics. The apparent first-order rate constant, k1', value increases with temperature. Apparent activation energy of decolorization was similar for both systems at ∼ 22 kJ mol(-1), while energy for laccase inactivation was 18 kJ mol(-1). Although both systems were endothermic, fungal biomass showed higher enthalpy, entropy, and Gibbs free energy changes for the decolorization compared to free laccase. On the other hand, free laccase showed reaction spontaneity over a wider range of temperature (ΔT = 40 K) as opposed to fungal biomass (ΔT = 15 K). Comparison of entropy change (ΔS) values indicated metabolism of the dye by the biomass.

A study was carried out to optimize selected parameters for decolorization of a triarylmethane dye, such as crystal violet by white rot fungus, Pycnoporus sanguineus, pellets. The parameters studied were initial dye concentration (ppm), agitation speed (rpm), and process time (days) and were optimized using response surface methodology (RSM). It is shown that process time, agitation speed, and their interactions have significant effects on the decolorization process. Following the optimization, the decolorization study was extended to a stirred tank reactor (STR) process. Effects of different geometry of impellers on the decolorization process and power consumption were studied. Novel impeller geometries, such as 180 • curved blade and 60 • angled blade impellers, were used in the STR. The application of 180 • curved blade impeller resulted in higher percentage of decolorization at a relatively less power consumption as compared with 60 • angled blade impeller.

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