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 (approximate to 240 nm) were observed, contrasting with significantly larger sizes (approximate to 1.8 mu m) 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 approximate to 120 cm3 m-2 24 h-1 to approximate 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. This study investigates the effect of the hydrolysis process on bacterial cellulose (BC) to obtain bacterial cellulose nanocrystals (BCNCs) used to create high oxygen barrier nanocomposite coatings for food packaging applications.