Design of Lignin-Based Biofunctional Materials and Their Applications

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Highly phenolic lignin derivatives (lignophenol derivatives) with different phenolic functionalities were synthesized directly from native lignins, through the phase-separation process using phenol derivatives and concentrated acid. The relationships between the structures of lignophenol derivatives and their functions for proteins were discussed.Lignophenol derivatives had much higher affinities for proteins, compared with conventional lignins : -10 and -100 times higher in lignomonophenols and lignopolyphenols, respectively. The protein affinity was significantly affected by the substitution pattern of phenolic hydroxyl groups and was decreased by the introduction of hydrophobic alkyl substituents. The protein adsorbing capacities of lignophenol derivatives differed with the species from which they were derived. The maximum protein adsorption was achieved at the isoelectric points of used proteins. The lignophenol derivative-protein complex was rapidly and perfectly separated into lignin and protein moieties in aprotic solvents, although it was very stable at any pH in aqueous solution.The enzymes immobilized on lignophenol derivatives retained high activity : especially an enzyme on lignocresol comparable to a native one. The activity patterns had good correlations between native and immobilized enzymes.