Laccase-assisted grafting of poly(3-hydroxybutyrate) onto the bacterial cellulose as backbone polymer: Development and characterisation

Abstract

Bacterial cellulose (BC) exhibits high purity, mechanical strength and an ultra-fine fibrous 3-D network structure with bio-compatible and bio-degradable characteristics, while P(3HB) are a bio-degradable matrix material derived from natural resources. Herein, we report a mild and eco-friendly fabrication of indigenously isolated P(3HB) based novel composites consisting of BC (a straight-chain polysaccharide) as a backbone polymer and laccase was used as a grafting tool. The resulting composites were characterised by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analyser (DMA) and water contact angle analyser (WCA). The FTIR spectra of the pure P(3HB) and P(3HB) containing graft composites [P(3HB)-g-BC] showed their strong characteristic bands at 3358cm−1, 1721cm−1 and 1651cm−1, respectively. A homogenous dispersion of P(3HB) in the backbone polymer of BC was achieved as evident by the SEM micrographs. XRD pattern for P(3HB) showed distinct peaks at 2θ values that represent the crystalline nature of P(3HB). While, in comparison with those of neat P(3HB), the degree of crystallinity for P(3HB)-g-BC decreased and this reduction is mainly because of the new cross-linking of P(3HB) within the backbone polymer that changes the morphology and destroys the crystallites. Laccase-assisted graft composite prepared from P(3HB) and BC was fairly flexible and strong, judged by the tensile strength (64.5MPa), elongations at break (15.7%), and Young's modulus (0.98GPa) because inherently high strength of BC allowed the mechanical properties of P(3HB) to improve in the P(3HB)-g-BC composite. The hydrophilic property of the P(3HB)-g-BC was much better than that of the individual counterparts which is also a desired characteristic to enhance the biocompatibility of the materials for proper cell adhesion and proliferation.