Numerical simulation and application of nano-magnetic enzyme hydroenzymatic method for soybean oil and grease extraction in a magneto-fluidized bed

Abstract: Soybean oil has been one of the most consumed cooking oil extracted from the seeds of the soybean. Aqueous and enzymatic processes can be widely expected for edible oil extraction in recent years. In this study, a series of numerical simulations were carried out to determine the optimum parameters for the aqueous and enzymatic oil extraction from a magnetic fluidized bed under the OpenFOAM software, in order to improve the oil quality, yield, and extraction rate of soybean. The free cellulase was also immobilized on a magnetic polymer carrier Fe3O4/SiOx-g-P (GMA) using the glutaraldehyde cross-linking protocols. The carrier was prepared using ethyl orthosilicate and 3-aminopropyl triethoxy, while, the Fe3O4 nanoparticles were modified by silane. The magnetically immobilized cellulase with the better magnetic response was obtained for the subsequent flow of magnetizing application in the fluidized bed and the separation after the reaction. Scanning electron microscopy (SEM) images showed that the rough and uneven surface of the carriers significantly increased the surface area of the magnetically immobilized cellulase for the better adsorption of the enzyme. The particle size analysis and SEM images revealed that the particle size of magnetically immobilized cellulase was outstandingly enlarged with a more uniform morphology, compared with the carrier. Correspondingly, Fourier infrared spectroscopy (FIS) verified that the magnetically immobilized cellulase was immobilized on the polymer carrier Fe3O4/SiOx-g-P (GMA). The enzymatic properties of the immobilized cellulase and the free enzyme were evaluated to determine the optimum pH (5) and temperature (60 ℃) of the immobilized cellulase, indicating that the higher heat, acid, and alkali resistance of the cellulose than before immobilization. The discrete element method (DEM) was used to construct a two-dimensional numerical model of nano-magnetase particles. The OpenFOAM software was selected to obtain the best parameters of hydroenzymatic oil extraction in a magnetic fluidized bed. An optimal combination was achieved for the magnetase with the fluidized state in the fluidized bed, the maximum reaction contact surface, and the maximum oil extraction rate, where the fluid flow rate was 0.0041m/s, and the magnetic field strength was 0.034 T. The instantaneous distribution and speed of the magnetase motion were also measured to clarify the influence of the magnetic field intensity on the magnetase motion trajectory. These optimal parameters were then applied to the circulating magnetic fluidized bed for the water-enzymatic extraction of oil. In addition, a single factor experiment was conducted to optimize the processing parameters for the oil extraction from the magnetic fluidized bed. Specific parameters were gained for the highest extraction rate of soybean oil, where the addition amount of magnetically immobilized cellulase was 1.2 mg/g, the pH value was 5, and the temperature was 55 ℃, and the reaction time was 120 min. The rate of oil extraction from the magneto-fluidized bed increased by 6.1%, compared with the conventional intermittent reaction. Magnetically immobilized cellulase was used continuously in a magnetic fluidized bed for 12 hours, where the magnetase activity remained above 80%. The finding can provide the basic theoretical support for the environmental performance of the oil process, particularly for the subsequent industrialization of enzymatic oil extraction from the magnetic fluidized bed in the vegetable oil industry.