Kinetic modeling of the production of fatty acids using lipases from castor bean powder as biocatalyst

Abstract

This work provides experimental data and mathematical modeling of the hydrolysis reaction of high oleic sunflower oil catalyzed by lipase powder (LP) from castor bean seeds. The production of fatty acids (FA) at different times (0.5–48 h), temperatures (30–50 °C) and concentrations of LP (0.006 and 0.012 gLP/goil) was experimentally tested. As expected, an increase in LP concentration and reaction temperature caused an increase of the initial reaction rate. The highest FA concentrations at long reaction times were obtained using 30 and 37 °C, while 45 and 50 °C showed a marked lipase thermal inactivation. Despite this, thermal inactivation effects were still detected at 37 °C using 0.006 gLP/goil, although undetected at the highest tested LP concentration. Two mathematical models were used to fit the experimental data in order to analyze FA production at tested conditions. The first one was a hyperbolic empirical model for FA concentration as a function of reaction time, which permitted the estimation of initial reaction rates and comparisons with similar reaction systems. Furthermore, a first principles model of a chain reaction system, including temperature inactivation, was also applied and kinetic constants were estimated as Arrhenius-type temperature functions. Results showed that both proposed models provided good mathematical representations of the hydrolysis reaction of high oleic sunflower oil catalyzed by LP from castor bean at the specific studied conditions. Although the second one is far more complex, it allows to predict the behavior at different conditions within the analyzed ranges, describing not only the final product (FA) but also the intermediate ones. Furthermore, this proposed first principles model was successfully validated against published experimental data. Thus, depending on the requirements and available data, both models could be helpful tools to represent and/or study the hydrolysis catalyzed by lipases from castor bean seeds.