Deproteinized natural rubber latex and preparation method
A deproteinized natural rubber latex and preparation method thereof are provided. A combined immobilization technology of a multi-enzyme system is introduced to form a multi-enzyme synergistic effect, such that high-concentration enzymes contact with proteins in natural rubber latex. Meanwhile, due to the complexity and diversity of latex proteins, the catalytic properties of different enzymes are effectively combined to realize a multi-enzyme cascade reaction, and the proteins are hydrolyzed gradually and orderly. In addition, an immobilized enzyme filter screen is introduced, and the filter screen is lifted and circulated to make rubber particles collide with high-density enzyme carrier and then complete mixing evenly to reduce damages to the rubber particles when surface proteins are removed, thereby maintaining original physical properties of the latex. The rubber latex has high stability, reusability, is easy for separation and continuous operation, and is environmentally friendly.
1 . A method for preparing a deproteinized natural rubber latex, comprising:
compounding mesh gauze with an adsorption medium solution, and conducting adsorption to obtain enzyme carrier gauze;
immersing the enzyme carrier gauze in four solutions, each containing one of four different enzymes, respectively, to conduct enzyme adsorption; conducting cross-linking immobilization on each treated gauze in a cross-linking agent solution to obtain mono-layer immobilized enzyme filter sheets corresponding to each of the four different enzymes; and
laminating the mono-layer immobilized enzyme filter sheets corresponding to each of the four different enzymes to obtain an immobilized enzyme filter screen; wherein the four different enzymes are selected from the group consisting of protease, peptidase, phospholipase, and lipase;
mixing natural rubber latex, water, and nonionic surfactant, adding a gluconolactone solution to a resulting mixture, and conducting recirculating filtration on a resulting mixed solution by lifting and dropping the immobilized enzyme filter screen until a pH value is 3 to 6 to obtain a post-enzymolysis latex; and
mixing the post-enzymolysis latex, a water-soluble polymer, and an anionic surfactant, adjusting a resulting mixture to a pH value of 9 to 11, conducting solubilization, and conducting centrifugal separation to obtain the deproteinized natural rubber latex.
2 . The method of claim 1 , wherein the mesh gauze is woven with one or more materials selected from a group consisting of silk braided wire, pure cotton braided wire, and pineapple fiber yarn, and the mesh gauze has a mesh pore size of 0.1 cm to 2.0 cm, a braided wire strength of greater than 25 MPa, and an elongation rate of less than 20%;
the adsorption medium solution is one or more selected from a group consisting of a regenerated silk fibroin solution, a polyethyleneimine solution, a dopamine hydrochloride solution, a sodium alginate solution, and a chitosan solution; and
the adsorption is conducted at 0° C. to 45° C. for 10 min to 300 min.
3 . The method of claim 1 , wherein the protease is one or more selected from a group consisting of alkaline protease, neutral protease, bromelain, papain, trypsin, thermolysin, staphylococcal protease, and clostripain;
the peptidase is one or more selected from a group consisting of exopeptidase, aminopeptidase, and carboxypeptidase; and
the phospholipase is one or more selected from a group consisting of phospholipase A, phospholipase B, phospholipase C, and phospholipase D.
4 . The method of claim 1 , wherein a cross-linking agent in the cross-linking agent solution is one or more selected from a group consisting of: glutaraldehyde, glyoxal, terephthalaldehyde, and genipin;
the cross-linking agent solution has a concentration of 0.05 wt % to 3.5 wt %, a pH value of 7.0 to 9.5, and a dosage of 3 g/g mesh gauze to 10 g/g mesh gauze; and
the enzyme adsorption and the cross-linking immobilization each are conducted independently at 0° C. to 45° C. for 10 min to 300 min.
5 . The method of claim 1 , wherein the deproteinized natural rubber latex has a dry rubber content of 1.0% to 65% by mass and a pH value of 8.0 to 12.0.
6 . The method of claim 1 , wherein the nonionic surfactant is any one or more selected from a group consisting of: Tween, Span, trehalose, stachyose, glucoside, nonylphenol polyoxyethylene ether (NPE), iso-tridecanol polyoxyethylene ether, and alkyl polyglucoside, and the nonionic surfactant has a weight percent of 0.01% to 10% of the natural rubber latex;
the gluconolactone solution has a concentration of 1 wt % to 10 wt %, and gluconolactone in the gluconolactone solution has a weight percent of 0.01% to 10% of the deproteinized natural rubber latex.
7 . The method of claim 1 , wherein when the recirculating filtration is conducted, the immobilized enzyme filter screen is automatically lifted and dropped at a lifting speed of 1 cm/s to 20 cm/s for 3 h to 6 h when a vertical axis is fixed; and
after the recirculating filtration is completed, a filtrate is allowed to stand for 3 h or longer.
8 . The method of claim 1 , wherein the water soluble polymer is one or more selected from a group consisting of: polyethylene glycol, methoxy polyethylene glycol, polypropylene glycol, methyl polypropylene glycol, polyethylene oxide, polyethylene oxide ether, polyvinyl alcohol, a polyvinyl alcohol copolymer, ethyl hydroxyethyl cellulose, methyl cellulose, polyacrylamide, a polyacrylamide copolymer, polyacrylic acid, sodium polyacrylate, polypropylene oxide, and polyglycerol-glycidyl ether-polyvinyl alcohol, and the water soluble polymer has a weight percent of 0.01% to 10% of the deproteinized natural rubber latex;
the anionic surfactant is one or more selected from a group consisting of: diphenyl ether sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, naphthalene sulfonate, alkyl sulfonate, dialkyl sulfosuccinate, a-alkene sulfonate, a-sulfonated fatty acid salt, alkyl sulfate, polyoxyalkylene stilbene phenol sulfate, polyoxyalkylene sulfonate, triphenylethylene phenol sulfate, polyoxyalkylene phenyl ether sulfate, alkyl sulfate, polyoxyalkylene alkyl sulfate, polyoxyalkylene alkylphenyl ether sulfate, polyoxyalkylene tristyrenated phenol sulfate, and polyoxyalkylene distyrenated phenol sulfate;
the anionic surfactant has a weight percent of 0.01% to 10% of a dry rubber content of the deproteinized natural rubber latex; and
the solubilization is conducted for 3 h to 6 h.