The Relationship Of Properties And Structure Of Rice Dreg Protein And Its Separation And Purification

The protein was extracted from the rice dreg in this study.Comparing different extract method(alkali,a-amylase,protease,diluted alkali),the alkaline-a-amylase extraction and diluted alkali degreasing-thermos table amylase were used to extract the rice dreg protein finally,when considering the purity and yield.Optimizing the extract conditions of these two methods,the purity of rice dreg proteins(alkaline extraction protein and diluted alkali degreasing protein)were 88.65%(dry basis 93.59%)and 89.46%(dry basis 93.39%),respectively.The content of glutamic was the highest in both of the proteins.Valine and leucine were essential amino-acid,and the contents of those are nearly 10%.The functional properties(solubility and emulsifying properties)of protein were measured in this study.The results showed that,from pH 2.0-11.0,the solubility and emulsifying properties of two samples decreased firstly,and then increased.However,alkaline extraction protein exhibited better solubility and emulsifying properties than diluted alkali degreasing protein sample.To better investigate the differences of their functional properties,the aggregation changes of protein were studied by measuring surface hydrophobicity,particle size distribution,molecular weight and microstructure.The alkaline extraction sample had higher surface hydrophobicity and smaller particle size.From the scanning microscopy analysis,it displayed that the alkaline extraction was gathered,and the surface was rough.However,the diluted alkali degreasing was united by cross-linked granule,and the surface of the granule was smooth.It was indicated that the protein extracted by above methods formed different aggregate state.Alkaline extraction protein showed smaller aggregate particles,and exposed more hydrophobic groups,showing higher surface hydrophobicity than that of diluted alkali degreasing.As a result,the solubility and emulsifying properties of alkaline extraction were better.This paper has explored gel filtration chromatography to separate and purify the two kind of rice dreg protein.The alkaline extraction protein dissolved in Na2CO3-NaHCO3(pH 10.83)system was separated,and three elution peaks(Protein I,II,III)which separated better were collected.The circular dichroism(CD)analysis revealed that the content of a-helix in three protein isolates were all lowest.The main secondary structure in protein I and II was random coil,which in protein III was ?-sheet.