Laccase-mediated Modification Of Regenerated Protein Fibers From Wheat Gliadin

Wheat gliadin, a major components of wheat gluten, was a single peptide chain withoutintramolecular disulfide bonds, with a molecular weight rage between30kDa and70kDa.Wheat gliadin is an ideal raw material for preparing regenerated protein fibers because of itsproperties of unique viscoelasticity, good biocompatibility and biodegradability. Laccase is acopper-containing enzyme polyphenol oxidase. According to the mechanism of proteincatalyzed by laccase, free radicals are generated through electron transfer, which leading tofurther crosslinking reaction between proteins. In this study, regenerated protein fibers wereprepared via wet spinning from gliadin, which was extracted from gluten. And then the fiberswere modificated by laccase-mediated crosslinking reaction. The structure, mechanicalproperties, solution stability and thermal properties of the fibers catalyzed by laccase werediscussed. The effect of laccase/mediator system on gliadin modification were exploredbriefly as well.The results indicated that oxygen was consumed during the reaction process in thegliadin spinning solution induced by laccase and the higher molecular weight polymers wereformed by the crosslinking reaction between gliadin molecules. Gliadin fibers with betterproperties could be prepared in the spinning solution with30%gliadin concentration and1%reducing agent and the gliadin solution was aged for about24h to form a viscous dopesuitable for spinning. The optimum conditions of laccase-mediated modification were:0.2U/ml of laccase amount, pH5,50℃and2h. The fiber’s tenacity and elongation wererespectively increased30.87%and115.67%. Meanwhile the solution stability and thermalstability of the fibers were also improved. The analysis of FTIR indicated the ratio of randomcoils in secondary structure of gliadin fibers catalyzed by laccase was increased. SEM showedthat the surface morphology of fibers modified by laccase was improved.At last, ferulic acid was used as a mediator to investigate its effect on the reactioninduced by laccase. The results showed that the amount of oxygen was consumed morequickly and larger molecular weight polymers were produced in laccase/mediator system. Theviscosity and the average particle size of the protein in the solution were also improved. Inaddition, the tenacity of gliadin fibers was increased10.25%and the elongation was notaffected significantly.