Continuous Enzymatic Synthesis of 2-Ethylhexyl Oleate in a Fluidized Bed Reactor: Operating Conditions, Hydrodynamics, and Mathematical Modeling

Study of the biochemical and kinetic properties of Candida antarctica lipase immobilized on magnetized poly(styrene-co-ethylene glycol dimethacrylate) and the development of a mathematical model for emollient ester synthesis

The present study aimed to develop a biocatalyst through the immobilization of Candida antarctica lipase B (CALB) via physical adsorption onto magnetized poly(styrene-co-ethylene glycol dimethacrylate) (STY-EGDMA-M). Biochemical property characterization, apparent kinetic parameter determination, and thermal stability assessment were conducted using a methodology developed based on the hydrolysis of the ester methyl butyrate. The results demonstrated that immobilization expanded the enzyme's optimal pH range, with the best performance observed at pH 7.5 and 8, reaching approximately 730 U g⁻1. Additionally, increasing the temperature to 55°C led to an enhancement in the biocatalyst's hydrolytic activity, achieving a maximum of 916.24 U g⁻1. Kinetic parameter analysis yielded values of 321.38 ± 6.31 mM for Km and 4322.46± 75.73 U g⁻1 for Vmax. Thermal stability tests were conducted at 55°C, revealing that 83% of the biocatalyst's initial activity was retained after 24 h of exposure. Furthermore, the biocatalyst's performance in the synthesis of emollient esters (butyl oleate, 2-ethylhexyl oleate, and octyl oleate) via solvent-free esterification was evaluated. The synthesis of emollient esters demonstrated conversions exceeding 55% for octyl oleate and 2-ethylhexyl oleate at 50 and 55°C, whereas the maximum conversion for butyl oleate was 42% at 55°C. Among the bioprocesses evaluated, the synthesis of octyl oleate was selected for kinetic modeling using the ping-pong bi-bi mechanism, with five different parameter arrangements constructed. The model with the lowest corrected Akaike information criterion (AICC = 129.649) was selected. The findings obtained in this work open new avenues for biotechnological applications, reinforcing the relevance of the biocatalyst as a promising tool for industrial processes and scientific research. Additionally, this study provides an alternative methodology for the biochemical characterization of immobilized lipases and employs mathematical modeling to enhance the kinetic understanding of enzymatic reactions conducted at different temperatures.

Esters in the Food and Cosmetic Industries: An Overview of the Reactors Used in Their Biocatalytic Synthesis

Esters are versatile compounds with a wide range of applications in various industries due to their unique properties and pleasant aromas. Conventionally, the manufacture of these compounds has relied on the chemical route. Nevertheless, this technique employs high temperatures and inorganic catalysts, resulting in undesired additional steps to purify the final product by removing solvent residues, which decreases environmental sustainability and energy efficiency. In accordance with the principles of "Green Chemistry" and the search for more environmentally friendly methods, a new alternative, the enzymatic route, has been introduced. This technique uses low temperatures and does not require the use of solvents, resulting in more environmentally friendly final products. Despite the large number of studies published on the biocatalytic synthesis of esters, little attention has been paid to the reactors used for it. Therefore, it is convenient to gather the scattered information regarding the type of reactor employed in these synthesis reactions, considering the industrial field in which the process is carried out. A comparison between the performance of the different reactor configurations will allow us to draw the appropriate conclusions regarding their suitability for each specific industrial application. This review addresses, for the first time, the above aspects, which will undoubtedly help with the correct industrial implementation of these processes.

Development of a magnetically stabilized fluidized bed bioreactor for enzymatic synthesis of 2-ethylhexyl oleate

This study aimed to develop and investigate the synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on magnetic poly(styrene-co-divinylbenzene) (STY-DVB-M) particles in a magnetically stabilized fluidized bed reactor (MSFBR) operated in continuous mode. The physical properties of the copolymer were characterized by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The glass transition temperature was 85.68 °C, and the onset of thermal degradation occurred at 406.66 °C. Syntheses were performed at 50 °C using a space time of 12 h and a bed porosity of 0.892. Assays were conducted to assess the influence of magnetic field intensity (5 to 15 mT) on reaction yield, ester concentration, and productivity. The highest productivity was 0.850 ± 0.023 mmol g-1 h-1, obtained with a magnetic field intensity of 15 mT. An operational stability test was performed under these conditions, revealing a biocatalyst half-life of 2148 h (179 operation cycles) and a thermal deactivation constant of 3.23 × 10-4 h-1 (R2 = 0.9446). Computational simulations and mathematical modeling were performed using Scilab based on ping-pong bi-bi kinetics and molar balances of reaction species. The model provided consistent results of interstitial velocity and good prediction of reaction yields, with R2 = 0.926. These findings demonstrate that the studied technique can provide improvements in biocatalytic processes, representing a promising strategy for the enzymatic synthesis of 2-ethylhexyl oleate.