Research On On-line Monitoring And Ultrasonic Strengthening Technology For Decolorization Of Lycium Barburum Polysaccharides

Lycium barbarum have many functions and is an important material for homology of medicine and food.Lycium barbarum polysaccharide(LBP)is its main active ingredient.In the extraction process of LBP,various impurities such as large molecular glycoproteins,pigments,and small molecule organic substances insoluble in alcohol need to be eliminated and purified.Chromatographic decolorization is the purification operation for the production of high-quality LBP,but the traditional chromatography technology had the disadvantages of poor separation effect and low level of intelligence.This paper intended to apply near-infrared spectroscopy to the online real-time monitoring of the decolorization and adsorption process of the LBP column chromatography.With the help of acid-alkali sequential elution mode and ultrasonic strengthening technology,the desorption effect of the LBP decolorization and desorption process was improved.The main research contents and conclusions were as follows:(1)Screening of adsorption resin and optimization of chromatographic decolorization adsorption conditions.The crude polysaccharide solution of Lycium barbarum extracted by hot water extraction was used as raw material,and the recovery rate,decolorization rate and deproteinization rate of polysaccharide were used as indexes to screen the optimal resin by static adsorption method,and static adsorption kinetics,static adsorption model and thermodynamic parameters were studied.Response surface design was performed to optimize the adsorption conditions for chromatographic dynamic decolorization such as loading concentration,sample flow rate,and diameter-to-height ratio.The test results showed that D280 resin had the best decolorization effect among the six resins.The Webber-Morris kinetic model and Boyd kinetic model showed that the adsorption process of D280 resin by LBP pigment was caused by liquid film diffusion and internal particle diffusion.The two speed-limiting steps were jointly decided,and were more suitable for enhancing the mass transfer by using ultrasonic high-frequency perturbation.The optimal chromatographic decolorization adsorption conditions optimized by response surface were:loading concentration 0.43 mg/m L,diameter-to-height ratio 1:10.06,flow rate 1.99 BV/h,and the optimal decolorization rate at this time was 91.54%.Considering the feasibility of the experiment,the loading concentration was 0.4 mg/m L,the column diameter to height ratio was 1:10,and the injection flow rate was 2 BV/h.Under this condition,the decolorization rate was 91.49%and the polysaccharide retention rate was 86.32%.The deviation from the optimal decolorization rate obtained by the optimized design of the response surface is 0.055%.(2)Research on real-time monitoring technology of the adsorption process of the chromatographic decolorization of LBP.The spectral information in the decolorization and adsorption process of LBP was correlated with the decolorization rate and polysaccharide recovery rate measured by chemometrics,and a real-time monitoring method for the decolorization and adsorption process of LBP was established.Four spectral pretreatment methods,SNV,SG,1^st Der and 2^nd Der,were used to preprocess the spectral information collected during the dynamic decolorization process.The decolorization rate and polysaccharide recovery rate models were established by PLS,i PLS and Si-PLS.The experimental results were as follows:SG pretreatment method had the best effect and the Si-PLS model had the highest prediction accuracy.The correlation coefficients of the decolorization rate correction model and the prediction model were 0.9855 and 0.9959 respectively,and the RMSECV and RMSEP were 1.49and 0.79 respectively.The correlation coefficients of the polysaccharide recovery correction model and the prediction model were 0.9790 and 0.9897,respectively,and the RMSECV and RMSEP were 5.84 and 4.18,respectively,indicating that the monitoring system using Si-PLS modeling could be more predictive and more stable.(3)Study on the ultrasonic strengthening technology of the desorption process of the chromatographic decolorization of LBP.Aiming at the desorption regeneration process of LBP chromatography,the optimal model of desorption was firstly selected from separate acid desorption,separate alkali desorption and acid-alkali combined elution,and then the optimal ultrasonic parameters to improve the desorption effect of resin were optimized to further study the kinetic model of column desorption process.The results showed that the acid-alkali sequential elution of 5%HCl+0.1 M NaOH was the best,and the elution effect was 3.31 times that of 5%HCl alone and 1.52 times that of 0.1 M NaOH alone.The optimum conditions for ultrasonic to improve desorption effect were:frequency 20 k Hz,power 77.81 W,under which the effect of resin applied10 times was equivalent to that of resin applied 4 times without ultrasonic.D280 resin pigment desorption in line with BDST/Thomas/Yoon-Nelson model,the model desorption constant K value under ultrasonic condition was 9.38%higher than that without ultrasonic.