Enzymatic Hydrolysis of Bacterial Cellulose for the Production of Nanocrystals for the Food Packaging Industry.

Cesare Rovera,Silvia Trabattoni,Diego Romano,Stefano Farris,Filippo Fiori

doi:10.3390/nano10040735

Abstract

Bacterial cellulose nanocrystals (BCNCs) obtained by enzymatic hydrolysis have been loaded in pullulan biopolymer for use as nanoparticles in the generation of high-oxygen barrier coatings intended for food packaging applications. Bacterial cellulose (BC) produced by Komagataeibacter sucrofermentans was hydrolyzed by two different enzymatic treatments, i.e., using endo-1,4-β-glucanases (EGs) from Thermobifida halotolerans and cellulase from Trichoderma reesei. The hydrolytic activity was compared by means of turbidity experiments over a period of 145 h, whereas BCNCs in their final state were compared, in terms of size and morphology, by atomic force microscopy (AFM) and dynamic light scattering (DLS). Though both treatments led to particles of similar size, a greater amount of nano-sized particles (≈250 nm) were observed in the system that also included cellulase enzymes. Unexpectedly, transmission electron microscopy (TEM) revealed that cellulose nanoparticles were round-shaped and made of 4–5 short (150–180 nm) piled whiskers. Pullulan/BCNCs nanocomposite coatings allowed an increase in the overall oxygen barrier performance, of more than two and one orders of magnitude (≈0.7 mL·m−2·24 h−1), of pure polyethylene terephthalate (PET) (≈120 mL·m−2·24 h−1) as well as pullulan/coated PET (≈6 mL·m−2·24 h−1), with no significant difference between treatments (hydrolysis mediated by EGs or with the addition of cellulase). BCNCs obtained by enzymatic hydrolysis have the potential to generate high oxygen barrier coatings for the food packaging industry.

Highlights

Cellulose synthesized by plants or bacteria is an almost inexhaustible organic polymer resource on Earth and has global economic importance [1]
Bacterial cellulose nanocrystals (BCNCs) obtained by enzymatic hydrolysis have been loaded in pullulan biopolymer for use as nanoparticles in the generation of high-oxygen barrier coatings intended for food packaging applications
Pullulan/BCNCs nanocomposite coatings allowed an increase in the overall oxygen barrier performance, of more than two and one orders of magnitude (≈0.7 mL·m−2·24 h−1), of pure polyethylene terephthalate (PET) (≈120 mL·m−2·24 h−1) as well as pullulan/coated PET (≈6 mL·m−2·24 h−1), with no significant difference between treatments

Summary

Introduction

Cellulose synthesized by plants or bacteria is an almost inexhaustible organic polymer resource on Earth and has global economic importance [1]. CNCs are obtained through top-down processes (e.g., chemical, physical, and mechanical processes), which aim to isolate the crystalline phase from the amorphous regions of the parental, macro-sized cellulose fibers; the process eventually results in nano-objects characterized by high tensile strength, high length–diameter ratio, high specific surface area, and biodegradability [8]. For these reasons, CNCs represent an excellent alternative to the inorganic filler used in polymeric materials for the generation of nanocomposites. BCNCs were used for the generation of oxygen barrier bionanocomposite coatings, deposited on polyethylene terephthalate (PET) for the food packaging industry

Materials and Methods

Enzymatic Hydrolysis of BC

Analyses

Findings

Conclusions