Study On The Technology Of High Purity Protein Isolated From Rice Residues

Rice residue,a waste material of starch sugar and organic acid production,retained almost all the protein composition of rice and its protein content was more than 50%(dry basis),and it was a good raw material to extract rice protein.But due to the process of high temperature liquefaction the denaturation and structure of protein had changed,traditionally the extraction rate and the purity of alkaline extraction of protein from rice residue was both lower,and this protein may contain harmful substance;And during enzymatic extraction method of rice residue protein the active site of rice residue protein due to the aggregation of rice residue protein and the encapsulation between rice residue protein and starch granule was hidden and may result in reducing hydrolysis efficiency.On the other hand the mass of the ends of hydrophobic were exposed during the enzymatic hydrolysis of the protein,and formed a bitter small molecular peptide.In this paper,the lipase was used in the process of degreasing,?-amylase and cellulose was applied to the technology of deglycosylation,finally rice residue protein was prepared.This method can obtain protein from rice residue mostly and aim to achieve the effect of protein purification,and that do not destroy the protein primary structure avoiding the formation of bitter peptides.The concrete research content is as follows:Lipase can remove fat of rice dreg effectively.Conditions of degreasing rice dreg were optimized by response surface analysis.The results indicated that three conditions as pH value,temperature,addition of lipase had a significant effect on the degreasing rate of rice residue.The optimum conditions of degreasing were pH 8.9,temperature 39 ?,solid-liquid ratio 1:8,lipase added amount of 37.30 U/g,reaction time 70 min,and the result is that rice residue degreasing rate of 79.36%,the protein purity of 66.32%.Comparing the effect of desugar of high temperature ?-amylase,mesophilic ?-amylase and glucoamylase,mesophilic ?-amylase was chosen as main desugar enzyme.Considering the defatted rice residue not only contains about 15.53% insoluble sugars,but also the content of cellulose is as high as 7.32%.Therefore,The technology of deglycosylation by bi-enzyme(?-amylase and cellulase)was optimized by response surface analysis.The results showed that: pH value,bi-enzyme amount and ratio of bi-enzyme had significant effects on the content of protein isolate in deglycosylation rice residue,the optimum conditions of deglycosylation were pH of 5.9,bi-enzyme amount of0.61% and ratio of bi-enzyme of 1.95:1,temperature of 55?,reaction time of 120 min.And the protein content of the best optimal condition of rice residue protein isolate was86.63%,protein extraction yield was about 95.88%.Functional and structure characteristics of the high purity rice residue protein isolate were investigated.Amino acid analysis showed that the content of human body essential amino acids in rice residue proteinwas about 27.78% of the total amino acid;Structural analysis of rice residue protein isolate by CD spectrum and IR spectrum revealed that high temperature liquefaction caused damage to secondary structure of rice residue protein,and showed that ?-helix and ?-tum structure were destroyed,?-folding structure and irregularity curly structure were increased.Infrared analysis showed that some sugar remained in the rice residue protein after the desugar;SDS-PAGE showed that the component of the rice residue protein had no change,rice residue and rice residue protein both had seven bands,and among them the contents of 36?19?13KDa subunitwere higher,and rice protein only had five bands,15 KDa subunit was appeared in rice protein and67 KDa subunit was disappeared compared with rice residue protein.Microstructure observation indirectly proved the feasibility of purification process.The analysis of functional properties shows that the solubility,emulsification,emulsification stability,the ability of foaming and foam stability of protein isolated from rice residues are 3.32%?42%?13%?48%?22% respectively.