Lipase-catalyzed Synthesis Of Ferulate Starch Ester In Non-aqueous System

Ferulic acid starch ester is a new type of modified starch with some physiological functions.The advantage of ferulic acid starch ester is that it not only has the physiological functions of ferulic acid but also has the physicochemical properties of starch.In this thesis,the ferulic acid starch ester has been synthesized by lipase in non-aqueous system.The chemical structure of the product was confirmed by UV,FTIR and 1HNMR.An efficient procedure for the lipase-catalyzed esterification of starch has been established in a non-aqueous medium with 2A molecular sieves as dehydrating agent,.The substrate,lipase and solvent must be balanced for two days using 2A molecular sieves before using.The esterification of corn starch with ferulic acid was carried out at aw<0.01,Novozym435 lipase as catalysis and isooctane as reaction medium,a maximum The degree of substitution of 0.026 was obtained.The effects of reaction factors such as mole ratio of substrate,addition amount of lipase,reaction temperature and time on the degree of substitution were investigated.The degree of substitution of the product was determined by ultraviolet spectrophotometer.When molar ratio of ferulic acid ethyl ester to starch was 3:1 and the addition amount of lipase was 10%(based on mass of starch),ferulic acid starch ester with a maximum degree of substitution of 0.031 was obtained.The cosolvent could improve the The degree of substitution to 0.0456(dimethyl sulfoxide)and 0.0408(acetone),when the ratio of cosolvent to isooctane was 3:7?The effect of different kinds of metal ions on Novozym 435 catalytic properties were studied.The alkaline-earth metals(Mg2+?Ca2+ and Ba2+)showed a similar influence trend on Novozym 435 with a low-dose stimulation and high-dose inhibition,i.e.hormesis.For transition metal,such as Cu2+?Mn2+ and Zn2+,mild promotion took place at low metal concentrations and serious inhibition at high concentrations.while 10-4mol/L Mg2+ and 10-6mol/L Zn2+ could significantly improve Novozym 435 activity.Spectral analysis showed that 10"4mol/L Mg2+ was conducive to the mild increasing of a-helix/?-sheet contents and Novozym 435 transformed to a more flexible conformation.Whilst maintaining its basic secondary structure.Mg2+ increased the contact area of substrate onto Novozym 435 and the probability of enter into Novozym 435 active site,resulting in the enhancement of Novozym 435 activity.The antioxidant properties and physical properties of ferulic acid starch ester were studied.The results showed that ferulic acid starch ester had the ability to scavenge hydroxyl radical,DPPH radical,superoxide anion.At the same time,the capacity,solubility,transparency of ferulic acid starch ester was significantly enhanced and the viscosity of ferulic acid starch ester was slightly reduced compared with the original starch.This trend was decreased with the increasing of The degree of substitution of ferulic acid starch ester.