Modeling, Simulation And Optimization Of Ultrasonic-Enzyme Assisted Continuous Countercurrent Extraction Of Astragalus Polysaccharide

With the development of modern food and drug industry,continuous countercurrent extraction（CCE）has been widely used in the extraction of natural product.However,due to the resistance of mass transfer during extraction,there are still problems such as excessive equipment flow and unstable product quality.The application of complex enzymes and ultrasound to reducing mass transfer resistance of CCE is one of the effective solutions,which is safe,environmentally friendly and sustainable.In this study,Astragalus polysaccharides（APS）,with immune regulation,myocardial protection and metabolism promotion,were used as extraction objects.Firstly,through the static extraction of APS,the ultrasonic and enzyme assisted combination methods and extraction parameters were optimized.The interaction between key factors in the extraction process is discussed in depth.Secondly,for optimal process migration and amplification in CCE,the mathematical model of diffusion backmixing is established and solved,and the two phase solute distribution in the pilot scale single flow continuous countercurrent extractor is described.Thirdly,two neural network models describing the the relationship between ultrasonic coupling enzymatic strengthening and phase internal diffusion coefficient were embedded in the hybrid model,which was used to describe the solute distribution of CCE under the two strengthening methods.Fourthly,based on the hybrid model,the flow field,ultrasound field and mass transfer field in a small single screw CCE device are simulated.The intensity and uniformity of multiphysics distribution were optimized by improving the propulsion mode and transducer arrangement.The conclusions obtained in this paper are as follows:（1）The extraction rate of ultrasonic coupling enzymatic extraction assisted extraction is better than that of step extraction.The suitable parameters are:ultrasonic power 30 W-50 W,extraction temperature 50°C-70°C,extraction time 40min-60min,solid-liquid ratio 1:8-1:12,with cellulase and pectinase hydrolysis.The optimal process conditions were obtained by the response surface Box-Behnken design:solid-liquid ratio 1:11,extraction time 50min,ultrasonic power 45 W,temperature 50°C,under which the extraction rate of APS was 6.49%.There is a significant interaction between solid-liquid ratio and ultrasonic power,extraction temperature and ultrasonic power.（2）A mathematical model for the two-phase solute distribution in a single-flow continuous countercurrent extractor for pilot scale is established.It was verified by multi-effect simulation CCE of APS.The results show that the relative error between the prediction and actual is within 15%at the temperature of 40°C-70°C,solid-liquid ratio of1:6-1:14,extraction time of 40 min-70 min.（3）It has been verified that the relative error of the ANN,which are used to describe the relationship between the ultrasonic coupling enzymatic and the diffusion coefficient in the phase,are less than 2%.Further,two ANN are embedded in the mathematical model to realize the description of the concentration distribution of the ultrasound coupling enzymatic assisted CCE.（4）The simulation results of multi-physics in a small single-screw CCE device show that,the use of perforated blades significantly reduces the range of stagnant zones in the extraction space compared to the enclosed one,at the same time,flow rate difference is reduced by 42.15%,and the minimum flow rate is increased by 69 times,which can effectively reduce the occurrence of solvent short circuit and improve the uniformity of the two-phase flow field.Preferably,when the power of the dual ultrasonic transducers is 50 W,the circumferential crossing is 90°,and the axial spacing is 12 cm,the acoustic interference from the two transducers is favorable for the uniform distribution of the far field sound pressure.At the same time,the sound pressure in the area of 72.28%in the extraction space exceeds 80 kPa,and the sound intensity in the area of 69.10%exceeds 20 kW/m².The simulation results of mass transfer field under the optimized physics show that the mass transfer flux of more than 62.5%reaches 5×10^-66 s^-1,which is the ideal mass transfer condition.It provides a theoretical guidance for the industrial amplification of ultrasonic coupling enzymatic assisted CCE.