The Studies On Development And Utilization Of Silk Protein

Silk is a natural protein, which is one of the earliest used by human. It is known as "FiberQueen" and rich in protein resources. This paper studied on two contents with silk protein asraw material: degumming sericin and optimizing hydrolysis condition. Silk contains a largenumber of protein, which is divided into two parts of sericin and fibroin. First, theanti-ultraviolet effect, emulsification activity, scavenging oxygen radical activity and the rateof degumming were selected to compare in order to choose which degumming method wasbetter–alkaline or enzymatic. Second, fibroin was hydrolyzed by NaOH, and then theoptimum conditions were determined by orthogonal experiments. Seven different proteases,which were flavourzyme, bromelain, acid protease, protamex, neutrase, papain and alcalasewere selected to hydrolyze remaining silk fibroin. The best protease was chosen with degreeof hydrolysis. The hydrolysis conditions were optimized and the the optimum conditions weredetermined by orthogonal experiments. The hydrolysate of silk fibroin was compared withdifferent Vc-adding amount by scavenging hydroxy radical activity. Following, thehydrolysate of silk fibroin was separated by Sephadex G-25. Then the molecular weight andthe scavenging hydroxy radical activity of each constituent was measured. The activity ofCAT, SOD and the content of MDA in the liver of mouse were measured according to animalexperiment.The experiment results indicated: the anti-ultraviolet effect, emulsification activity andscavenging oxygen radical activity of enzymatic method was better than alkaline method. Inthe meaning-while, the the rate of degumming of enzymatic method was lower than alkalinemethod. The optimum conditions of alkaline hydrolysis were determined by orthogonalexperiments, which were6%NaOH, solid-liquid ratio of1:100, at a temperature of60℃, for3hours. The silk fibroin could be best hydrolyzed by acid protease in above seven proteases. Soacid protease was chosen to hydrolyze silk protein. The optimum conditions of acid proteasehydrolysis were determined by orthogonal experiments, which were amount of enzyme8000u/g, pH3.8, at temperature of50℃, solid-liquid ratio of1:200for4.5hours. The amino nitrogen content was960μg/ml in the hydrolysate. Finally, the degree of hydrolysis was16.8%, and the scavenging hydroxy radical activity was more than Vc. The hydrolysate of silkfibroin was separated into two constituents by Sephadex G-25, which were2965Da with67.52%scavenging hydroxy radical activity, and1434Da with14.76%scavenging hydroxyradical activity. By animal experiment, the activity of CAT and SOD of the low, middle, highdosage groups were enhanced obviously (P<0.01) and the content of MDA of the low, middle,high dosage groups was significantly decreased (P<0.01) than the standard group. So, thehydrolysate of silk fibroin can improve the ability of anti-oxidation internal obviously.