Because branched or grafted biological polymers are often appeared in nature and such complicated structures contribute to exhibiting important in vivo functions, synthetic method for combining several biological polymers into branching or grafting is expected to produce new functional polymers. On the basis of the viewpoint, we have report the synthesis of amylose-grafted heteropolysaccharides by chemoenzymatic approach, which is a combined method of phosphorylase-catalyzed enzymatic polymerization of α-D-glucose 1-phosphate (G-1-P) monomer for the amylose production with appropriate chemical reactions. In this study, we synthesized amylose-grafted poly(γ-glutamic acid) (PGA) as a new graft copolymer by chemoenzymatic approach (Scheme 1). Maltooligosaccharide as a primer of the enzymatic polymerization was first introduced on PGA by condensation reaction using condensing agent in NaOH aq. Phosphorylase-catalyzed enzymatic polymerization of α-D-glucose 1-phosphate as a monomer was then performed from the chain ends of primers on the product to obtain amylose-grafted PGA, which formed hydrogels in reaction media depending on G-1-P/ primer feed ratios. The hydrogels showed high water retention ability as more than 90 % of the water contents. The XRD pattern of a cryogels, prepared by lyophilization of the hydrogels, suggested that amylose formed double-helix, which probably acted as crosslinking point for hydrogelation. The SEM images of the cryogels showed porous morphology. Moreover, the pore sizes of hydrogels increased as increasing the G-1-P/ primer feed ratios. Longer amylose chains are produced with increasing the feed ratios, resulting in the formation of looser networks.

Chemoenzymatic synthesis and gelation behavior of amylose-grafted poly(γ-glutamic acid)

253rd National Meeting (2017)

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