Enzymatic polymer modification

In the area of enzymatic polymer synthesis, one can distinguish between enzymatic polymerization and enzymatic polymer modification. Of the six main enzyme groups (see Table 3.3), three have been used as catalysts for enzymatic polymerization and four have been used in enzymatic polymer modification reactions. 

Challenges for Enzymatic Surface Modification of Synthetic Polymers... 

Enzymatic surface modification limits to the surfaces of polymers. 

Very few reports are available for the enzymatic surface modification of synthetic fibers. Peroxidase, lipase, cutinase, nitrilase, nitrile hydratase, amidase, protease, and hydrolase have been reported for the surface modification of synthetic polymers (Table 4.1). 

Another field of enzymatic polymer synthesis is the enzyme-catalyzed modification of preformed polymers by esterification or transesterification. Thereby, it is possible to either introduce functional side groups into an existing polymer with a stable backbone (no polyester) to synthesize functional homopolymers as well as random copolymers or to generate multiblock copolymers by enzymatic transesterification between two different homopolymers. 

Polymer Modification by Oxidoreductases. Tyrosinase (polyphenol oxidase, a copper-containing monooxygenation enzyme) was used as catalyst for modification of chitosan. The enzymatic treatment of chitosan film in the presence of tyrosinase and phenol derivatives produced a new material of chitosan derivative (309). During the reaction, imstable o-quinones were formed, followed by the reaction with chitosan to give the modified chitosan. In the enzymatic treatment of p-cresol with a low concentration of chitosan (<1%), the reaction solution was converted into a gel (310). 

To improve collagen s potential as a biomaterial, it has been modified or combined with other resorbable polymers. Modifications like cross-linking, addition of bioactive molecules, and enzymatic pretreatment have resulted in novel coUagen-based materials with improved fimctionality [10, 11]. Moreover, to facilitate the formation of fibers for biomedical textile applications, composite materials combining coUagen with other resorbable polymers like PLA, PLGA, and PCL have been studied extensively [12-15]. 

The enzymatic methods for polymer modification rely on the high specificity of the biocatalysts at mild reaction conditions to achieve targeted functionalizations. 

This overview briefly surveys the use of enzymatic and wholecell approaches in polymers. Three types of reactions are covered polymer syntheses, polymer modifications, and polymer hydrolyses. Thus far, most of the enz3une-related R D activities involve hydrolases, oxidoreductases, and transferases, with occasional use of lyases and isomerases. Whole-cell methods continue to be valuable in both academic and industrial labs. All these research areas display continued vitality and creativity, as evidenced by the large number of publications. Advances in biotechnology have provided new and improved enzymes and additional tools. Also included in diis overview is the related topic of biomaterials. 

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

Peng Y, Liu HW, Zhang XY, Li YS, Liu SY (2009) CNT templated regioselective enzymatic polymerization of phenol in water and modification of surface of MWNT thereby. J Polym Sci A Polym Chem 47(6) 1627-1635... 

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