Enzymatic and Chemical Cross-Linking of Bacterial Cellulose/Fish Collagen Composites—A Comparative Study

Agata Sommer,Hanna Staroszczyk,Paulina Dederko-Kantowicz,Sławomir Sommer,Marek Michalec

doi:10.3390/ijms22073346

Abstract

This article compares the properties of bacterial cellulose/fish collagen composites (BC/Col) after enzymatic and chemical cross-linking. In our methodology, two transglutaminases are used for enzymatic cross-linking—one recommended for the meat and the other proposed for the fish industry—and pre-oxidated BC (oxBC) is used for chemical cross-linking. The structure of the obtained composites is characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and their functional properties by mechanical and water barrier tests. While polymer chains in uncross-linked BC/Col are intertwined by H-bonds, new covalent bonds in enzymatically cross-linked ones are formed—resulting in increased thermal stability and crystallinity of the material. The C2–C3 bonds cleavage in D-glucose units, due to BC oxidation, cause secondary alcohol groups to vanish in favor of the carbonyl groups’ formation, thus reducing the number of H-bonded OHs. Thermal stability and crystallinity of oxBC/Col remain lower than those of BC/Col. The BC/Col formation did not affect tensile strength and water vapor permeability of BC, but enzymatic cross-linking with TGGS improved them significantly.

Highlights

Bacterial cellulose (BC) is a linear β-(1→4)-D-glucose polysaccharide synthesized by aerobic non-pathogenic bacteria of the genus: Agrobacterium, Pseudomonas, Sarcina, Rhizobium, and Komagataeibacter [1]
BC/fish collagen (BC/Col) composites were prepared by immersing wet BC membranes in the Col solution
Σ, ε, and water vapor permeability (WVP) values obtained indicate the higher effectiveness of the enzymatic over the chemical cross-linking

Summary

Introduction

Bacterial cellulose (BC) is a linear β-(1→4)-D-glucose polysaccharide synthesized by aerobic non-pathogenic bacteria of the genus: Agrobacterium, Pseudomonas, Sarcina, Rhizobium, and Komagataeibacter (formerly Acetobacter) [1]. Single glucose chains, produced inside the bacterial body, extrude out through the pores present on their cell envelope; in the hierarchical crystallization process, they form subfibrils, and microfibrils, which bound to ribbons. The latter form a BC three-dimensional network structure, and numerous spaces between the fibers result in its highly porous surface [2,3]. The unique structure of BC leads to its remarkable properties, in both wet and dried forms [4,5] This polysaccharide is characterized by high chemical purity and crystallinity, as well as high mechanical strength and water absorption properties [4,6,7]. Due to these features and because of high biodegradability and biocompatibility, BC-based materials have gained interest in many industries, especially the medical, pharmaceutical, and food industries

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