Study On Large-scale Extraction Technology Of Fucoidan And Its Removal Of Heavy Metals

Fucoidan， specific water-solubility polysaccharide exsists in the intercellular organizationof brown seaweed, is built up essentially of4-linked sulfated α-L-fucose, as well as uronic acid,galactose, xylose, proteins et al, is also characterized by remarkable anionic polymer. Fucoidanhas been extensively studied due to its numerous interesting biological activities, includingantitumor, anticoagulant, antioxidant, antivirus and anti-inflammatory et al. The desirablebiological activities of fucoidan are closely related to its sulfate group, uronic acid and molecularweight. Kelp, extraction material of fucoidan, is pillar industries of national economic marinealga with high annual output Therefore, the process of kelp can improve the national andinternational market competitive ability of our economic seaweed.Nowadays, the safety of food make food quality safety arouse people’s high attention. Thepurification of fucoidan was mainly precipitated by hydroxide, ethanol or quaternary ammonium;kelp, as the raw materials of fucoidan, has been partly polluted by heavy metals with the rapiddevelopment of offshore industry, and its bioactivities decreased. To reduce production cost forlarge-scale extraction of safe, low pollution and low concentration heavy metals fucoidan, In thisarticle, we have done some research works on fucoidan as follows:The extraction process of fucoidan from kelp. The factors which affect the extraction ratioof fucoidan were investigated at4℃, including rate of material to liquid, extraction time andextraction times. The optimistic process was obtained by setting up orthogonal experiment, thedata was analysed by range and variance methods. The results demonstrated that the optimalextraction condition was as follows: temperature4℃, rate of material to liquid1:30, extracting5hours and extracting twice. The yield of crude fucoidan was4.27%, the composition of totalsugar and sulphate was36.35%and23.89%respectively.Large-scale membrane seperation process of fucoidan. Different operating parameterswhich affect membrane flux were studied. Fucoidan was ultrafiltrated by Labscale TFF Systemwith the ulrafiltration membrane of50,30and10kDa molecular weight cutoff (MWCO) at4℃and25℃respectively. The results showed that operating at25℃and0.1MPa would maximizethe flux, but fucoidan solution decayed easily under a long ultrafiltration at25℃, andmicroorganisms were the main cause of making fucoidan decay, the fraction whose averagemolecular weight (MW) beyond50kDa was predominated at both temperatures. Besides, thefraction whose MW beyond50kDa was highest at temperature4℃, the content of the fractions was as follows:(84.29±2.772)%(MW beyond50kDa),(5.364±0.406)%(MW range30to50kDa),(2.203±0.144)%(MW range10to30kDa),(4.187±0.856)%(MW smaller than10kDa).Study on removal of heavy metals from fucoidan. fucoidan whose MW beyond50kDa wasredissolved in EDTA aerated water solution for fully reaction between heavy metals and EDTA,then, ultrafiltrated by plate ultrafiltration membrane of5kDa MWCO at4℃. The results showeddemineralization was desirable using ultrafiltration, there were ion exchange and chelatingreaction between the competitive chelates EDTA and fucoidan, under the acidic condition, heavymetals such as As, Cr, Cu, Cd and Pb could be removed obviously except Ba.Preparation of low concentration metals fucoidan. During the extraction process, EDTA andhydrochloric acid were added into the extracts (diluted to pH3.0) until the reaction completed.The solution was ultrafiltrated with plate ultrafiltration membrane of50kDa MWCO. The result,after removing heavy metals by ultrafiltration under condition pH3.0and EDTA-Na20.4g/L,the yield of fucoidan was3.07%, the content of total sugar, uronic acid and sulphate was30.62%,7.84%and26.47%respectively. And heavy metals residues including Hg, As, Pb, Cr, Cu and Cdwere fallen to a lower level.