Study On Enzyme Catalytic Hydrolysis And Rosin Esterification Modification Of Starch

In order to deepen the research work of this laboratory,extend the application range of starch and deepen the deep processing technology of starch,tthe hydrolysis process of corn starch by?-amylase was treated with the low-frequency electromagnetic field(LF-EMF),and its principle was discussed.The microporous starch prepared by starch hydrolysis was used as a carrier for loading 2,4-dinitrophenol(DNP)and sustained drug release.The reaction conditions of lipase-catalyzed surface modification of cassava starch rosin acid were optimized,and the structure and physicochemical properties of rosin starch ester were analyzed.The main research contents and conclusions were as followed:1.The 60 Hz LF-EMF was used to continuously irradiate the starch hydrolysis process of?-amylase to analyze the effect of LF-EMF on the efficiency of enzymatic starch hydrolysis.The mechanism of action of LF-EMF was discussed from substrate structure,enzyme structure and mass transfer of solution system.The results showed that LF-EMF radiation increased the efficiency of?-amylase catalyzed hydrolysis of corn starch,and it was initially determined that LF-EMF enhanced the reaction efficiency by strengthening the mass transfer,but the possibility could not be excluded that the LF-EMF radiation might affect the enzyme's conformation.2.The microporous starch prepared by?-amylase catalyzed hydrolysis of corn starch was used as a carrier,for DNP-loaded sustained release agent preparation,and the release performance in vitro was investigated too.The results showed that time of equilibrium adsorption of DNP to microporous starch was 1 h.Increasing the initial concentration of DNP and decreasing the adsorption temperature were beneficial to increase the adsorption amount.The kinetic and thermodynamic model fitting results showed that the adsorption of DNP onto microporous starch was the surface physical adsorption of van der Waals force and hydrogen bonding force,and the adsorption process was a spontaneous exothermic process.In the release experiment in vitro,DNP-microporous starch had a good sustained release effect compared with the drug substance.The release kinetic data analysis showed that the sustained release behavior of DNP-microporous starch accorded with the first-order kinetic model and mainly non-Fickian diffusion in artificial simulated gastric juice.The sustained release data accorded the Peppas equation and follows the Fickian diffusion mechanism in the intestinal fluid of the artificial body.3.Rosin acid starch(RAS)was prepared by rosin and native cassava starch as raw materials under lipase catalysis.The effects of mixed solvent type,solvent ratio,reaction time,material ratio of rosin acid to starch,reaction temperature and lipase dosage on the degree of substitution(DS)of RAS were investigated.On the basis of single factor experiment,the reaction conditions were optimized according to the principle of the combination Box-benhnken centered design and response surface methodology analysis.The mathematical model was established in RAS synthesis process.The optimum synthesis conditions were as follows:reaction temperature 59?,rosin-starch ratio of 4.1:1(w/w)and lipase-starch ratio of 264?L.Under this condition,the degree of substitution(DS)0.0608 was obtained.4.RAS were analyzed and characterized by Fourier Transform Infrared Spectroscopy(FT-IR),Nuclear Magnetic Resonance(~1H NMR),SEM(Scanning Electron Microscopy),XRD(X-ray Diffraction),Thermo Gravimetric Analyzer(TGA),contact angle,emulsifying ability and emulsion stability.The results of FT-IR and ~1H NMR was shown that the esterification reaction of rosin acid and starch successfully under the action of immobilized lipase.The TGA analysis showed that the thermal stability of the product after esterification were decreased with the increase of DS.The SEM analysis showed that the RAS retained the original spherical oval shape compared with the native cassava starch,while its surface became rough.XRD analysis showed that the crystallinity of RAS decreased compared with the native cassava starch,while the crystal form was still maintained type A.Compared with the native cassava starch,the contact angle,emulsifying ability and emulsion stability of RAS are improved,and the higher the DS,the more the exaltation.