Comprehensive Extraction And Purification Of Polysaccharide From Kelp Skirt

Kelp(laminaria japonica)is a natural food with high edible and medicinal values.It contains many active substances,such as fucoidan and sodium alginate that possess multiple biological activities.Therefore the kelp has become a hot research in recent years.The kelp resources are abundant in our country,however the utilization of kelp components is poor.Common products from the kelp include sodium alginate,iodine and mannitol.While the research of kelp fucoidan has not been intensively conducted,this leads to a serious waste of resources.Therefore,it has important practical significance to explore a method for efficient extraction of fucoidan and sodium alginate,which can improve the utilization of kelp resources and expand economic benefits.In this paper,kelp skirt was applied as material,the efficiency extraction method with complex enzyme of fucoidan and sodium alginate was established and compared with traditional hot water extraction method.The main results were listed as following.(1)Fucoidan extraction process optimization of complex enzyme method and hot water extraction: The complex enzyme method and hot water extraction method were used to extract the fucoidan and the extraction yields of fucoidan,total sugar and sulfate were was taken as the evaluation index.By single factor experiments and orthogonal test,the effects on the extraction yields of fucoidan were investigated,including enzymes dosage,temperature,time,pH,and liquid-solid ratio with complex enzyme method and temperature,time and liquid-solid ratio with hot water extraction method.The results indicated that complex enzyme contained cellulase,pectinase,xylanase,?-amylase,and acid protease in ratio of 18:11:11:1:5.According to the orthogonal test,the optimum extraction conditions of complex enzyme method were determined as complex enzyme 480 U/g,temperature 59 oC,pH 4.5,time 10 h,and liquid-solid ratio(mL/g)30.Under this condition,the average yield of fucoidan was 2.04%,while the extraction rate of fucoidan was 80.63%.In the extract,the content of total sugar and sulfate were 67.43% and 28.46% respectively.The optimum extraction condition of hot water extraction method was temperature 80 oC,time 20 h and liquid-solid ratio(mL/g)25.Under this condition,the average content of fucoidan was 0.84%,the extraction rate of fucoidan was 33.20%.i.In the extract the content of total sugar and sulfate were 36.30% and 28.46% respectively,which was significantly lower than that extracted by the complex enzyme method.(2)Purification of fucoidan: The fucoidan extracted by complex enzymes was purified by Sevage method and dialysis in sequence.Then the effects of deproteinization time and dialysis time on deproteinization and desalination were studied.The results indicated that 70.05% of the protein can be removed after handling twice by the Sevage method.Also,salt ions can be removed substantially by dialysing for 48 h.Finally,the contents of total sugar,sulfate and protein in the purified fucoidan reached 69.15%,28.99% and 1.12% respectively.(3)The kelp cell wall by compared complex enzyme method was found severely damaged by environmental scanning electron microscopy,while there were still a lot of intact cell existed after treatment by hot water extraction.The monosaccharide components of fucoidan extracted by the two methods were analyzed by precolumn derivatization HPLC method.The results showed that in the fucoidan extract by complex enzymes,the contents of L-Fuc and D-Gal were 27.18% and 18.12% respectively,which was higher than that of 13.17% and 9.69% respectively,by the hot water method of.The L-Rha and L-Gha of lowest contents were detected by the two methods.(4)Extraction of sodium alginate by complex enzyme-calcium coagulation-ion exchange: Sodium alginate and fucoidan were extracted at same time by the complex enzyme method.The effects of enzymes dosage,temperature,time,pH,and liquid-solid ratio on the extraction of calcium alginate.And the conversion yield from sodium alginate to calcium alginate was also compared by calcium coagulation-acidification and calcium coagulation-ion exchange method.The results showed that the extraction rate of sodium alginate by complex enzyme-calcium coagulation-ion exchange was 85.41%,which was higher 17.30% than that of 68.11% by the complex enzymes-calcium coagulation-acidification method.Also,all the indexes of sodium alginate were in accordance with national standard.