Acid-derived bacterial cellulose nanocrystals as organic filler for the generation of high-oxygen barrier bio-nanocomposite coatings

Abstract

Macro-sized bacterial cellulose (BC) derived from Komagataeibacter sucrofermentans was down-sized into nanocrystals (BCNCs) through hydrochloric acid (H-BCNCs) and sulfuric acid (S-BCNCs) hydrolysis. Initially, aqueous dispersions of BCNCs were analyzed for stability, size/morphology, and optical/mechanical properties. Subsequently, BCNCs were incorporated into a main biopolymer phase (i.e., pullulan) to create bio-nanocomposite coatings with high-oxygen barrier performance. Upon treatment with sulfuric acid, nano-sized particles (≈240 nm) were observed, contrasting with significantly larger sizes (≈1.8 μm) seen for particles obtained using hydrochloric acid. Microscopy analyses revealed a needle-like morphology of the nanocrystals, which appeared organized in stacks for H-BCNCs or as individual units for S-BCNCs. Pullulan/BCNCs coatings applied to polyethylene-terephthalate (PET) films improved the gas barrier performance of the original substrate, by dramatically reducing the oxygen transmission rate (OTR) values from ≈ 120 cm³ m⁻² 24 h⁻¹ to ≈ 2 cm³ m⁻² 24 h⁻¹ while preserving its original optical and mechanical properties. Our developed bionanocomposite-coated PET films hold potential as an alternative material for various food packaging applications.