Enzymatic synthesis of soluble …
Abstract The simple stirring of phenol with an oxidant in water provided a novel green way to synthesize soluble polyphenol
Enzymatic synthesis of soluble glucan fiber Info ..
Enzymatic reactions of horseradish peroxidase were used to polymerize phenols in various substrates, and the polyphenols were used for precious metal recovery. The phenol groups in polyphenols can reduce gold ions to gold particles at high capacities. Increasing the phenol group density in the polyphenol enhances the gold-reducing ability in acidic media. Poly(tyramine) produced by polymerization with horseradish peroxidase has oxidation and ion-exchange abilities and good solubility. Palladium and platinum ions were adsorbed on poly(tyramine) via ion-exchange interactions. Using the solubility of poly(tyramine), we propose a novel recovery system for gold ions. Because of the hydroxyl groups in the polymer, base metal ions, such as copper ions, were adsorbed in the pH region of 2-5.
The concepts of enzymatic polymer synthesis in surfactant systems with a focus on the synthesis of polyphenols and polyaromatic amines are presented. Phenolic polymers have a variety of conventional applications in making resins for coatings, laminates, etc. The traditional technology for making these polymers involves a formaldehyde-based high-temperature process, where undesirable side reactions lead to poor control of polymer structure and molecular weight. In addition, concern over the toxicity of formaldehyde necessitates the study of alternative technologies to produce such polymers. The enzymatic approach using an oxidative enzyme such as horseradish peroxidase eliminates the need for formaldehyde. The reaction has a mechanistic analogy to the synthesis of lignin and is illustrated through the simplified mechanism shown in Fig. 1a, where reaction is initiated by the addition of H2O2. Phenoxy radical centers initially formed on the monomer or growing chains migrate to the ortho positions (the para position, although mechanistically allowed, is less favored) after which coupling through condensation occurs. A molecular spacefilling model of polyphenol illustrates the curvature of the chains obtained when the hydroxyl groups lie on the same side of the polymer backbone. In the unfolded state, the polymer assumes an open structure.
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In principle, the enzymatically synthesized polyphe-nolics have similar applications to the phenol-formaldehyde resins that are chemically synthesized.1-13-1 However, there are unique aspects related to the enzymatically synthesized material. In contrast to phenol-formaldehyde polymers, these polyphenolics lack the intervening meth-ylene bridge between the aromatic groups, as illustrated in the simplified mechanistic scheme of Fig. 1a. The polymer is therefore conjugated and thus has a variety of potential applications in electro-optics. A specific property that is being investigated is the use of these materials in nonlinear optics (NLO), in particular for applications based on the optical third-order nonlinear susceptibilities (w(3)).[4,14] In such materials, higher-order terms become significant in the expansion of the material polarization (P) in terms of an applied electric field (E).
A unique and suitable environment for the enzymatic synthesis of polyphenols and polyaromatic amines is needed. The monomers are typically water insoluble, and therefore intrinsically incompatible with the water-soluble enzyme. Therefore, a unique system in which both enzyme and monomer are contacted efficiently is needed. One approach involves using a two-phase oil and water system; however, the agitation needed to enhance enzyme-monomer contact may shear-deactivate the enzyme. A second approach entails activating the enzyme in organic solvents, feasible for polyphenol synthesis.[4,6] A third approach encompasses the use of surfactants to incorporate water into an organic phase (or vice versa). This approach has the advantage that the enzyme and the monomer reside in close proximity and the enzyme experiences minimal agitation.
Cellulose Chemistry and Technology
Cellulose Chemistry and Tehnology ..
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Uyama H, Kobayashi S (2000) Enzymatic synthesis of soluble polyphenol.
Auclair S, Chironi G, Milenkovic D et al
Phenols - Wikipedia
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