Chitosan materials with entrapped enzyme and biocatalytic textiles and other biocatalytic materials comprising same
Methods of entrapping enzymes in chitosan matrices using mild conditions, such as methods that are compatible with the entrapment of acid-sensitive and/or heat sensitive enzymes, are described. The methods can provide biocatalytic materials with high chitosan to enzyme mass ratios where one or more enzymes can remain active and stably entrapped in the chitosan matrix for many months and/or after repeated washings. Also described are materials including a solid chitosan matrix having at least one enzyme stably entrapped therein, including fabrics, textiles and other flexible materials at least partially coated with one or more layer of the solid chitosan matrix having at least one enzyme stably entrapped therein and the use of the materials as biocatalyst systems, for example in biogas upgrading and other applications.
1. A method of preparing a chitosan matrix material comprising an entrapped enzyme, the method comprising:
providing an aqueous solution comprising dissolved chitosan, said aqueous solution having a pH of between about 2.5 and about 5.5;
adding at least one enzyme to the aqueous solution to provide a chitosan/enzyme solution, wherein the chitosan/enzyme solution comprises a mass ratio of chitosan to enzyme (on a dry basis) of greater than about 0.5; and
solidifying the chitosan to provide a solid chitosan matrix by one of:
(a) applying the chitosan/enzyme solution onto a solid support or substrate,
(b) applying the chitosan/enzyme solution to at least one portion of a surface of a textile substrate, or
(c) contacting the chitosan/enzyme solution with a coagulation solution;
wherein the at least one enzyme is stably entrapped within the chitosan matrix, thereby forming the chitosan matrix material.
2. The method of claim 1 , wherein providing the aqueous solution comprising dissolved chitosan further comprises:
(i) dissolving a protonated chitosan salt in a solution having a pH of between about 2.5 and 5.5; or
(ii) dissolving a solid chitosan in an aqueous solution comprising an organic acid and having a pH of between about 2.0 and about 4.5; and
(ii-a) adjusting the pH of the solution to between about 2.5 and about 5.5; or
(ii-b) drying the solution comprising the organic acid to provide a dry protonated chitosan and redissolving the dry protonated chitosan in a solution having a pH of between about 2.5 and about 5.5.
3. The method of claim 1 , wherein solidifying the chitosan comprises applying the chitosan/enzyme solution onto a solid support or substrate, wherein the applying comprises pouring, spreading, dipping, painting, rolling, padding, pressing, squeezing, extruding, spraying or printing; and drying the chitosan/enzyme solution to form a film or coating comprising a solid chitosan matrix.
4. The method of claim 1 , wherein solidifying the chitosan comprises applying the chitosan/enzyme solution to at least one portion of a surface of a textile substrate, and drying the chitosan/enzyme solution to form a film or coating comprising a solid chitosan matrix on the at least one portion of the surface of the substrate.
5. The method of claim 1 , wherein solidifying the chitosan comprises contacting the chitosan/enzyme solution with a coagulation solution thereby forming a solid chitosan matrix, wherein the at least one enzyme is stably entrapped within the solid chitosan matrix.
6. The method of claim 5 , wherein the method is free of: (i) the use of a covalent cross-linking agent reacted with the chitosan prior to, during, or both prior to and during the formation of the solid chitosan/enzyme matrix; and (ii) the addition of an additional polyanion to the chitosan/enzyme mixture; optionally wherein the method is further free of the use of collagen and/or wherein the at least one enzyme is an acid-sensitive and/or a heat sensitive enzyme.
7. The method of claim 1 , wherein the at least one enzyme remains active and stably entrapped within the chitosan matrix after repeated washings with water or a solution comprising water.
8. The method of claim 1 , wherein the at least one enzyme is selected from the group consisting of an oxidoreductase, a transferase, a hydrolase, a lyase, an isomerase, and a ligase.