Mechanical and structural properties of native and alkali-treated bacterial cellulose produced by Gluconacetobacter xylinus strain ATCC 53524

Abstract

Mechanical properties of hydrated bacterial cellulose have been tested as a function of fermentation time and following the alkali treatment required for sterilisation prior to biomedical applications. Bacterial cellulose behaves as a viscoelastic material, with brittle failure reached at approximately 20% strain and 1.5 MPa stress under uniaxial tension. Treatment with 0.1 M NaOH resulted in minimal effects on the mechanical properties of bacterial cellulose. Fermentation time had a large effect on both bacterial numbers and cellulose yield but only minor effects on mechanical properties, showing that the fermentation system is a robust method for producing cellulose with predictable materials properties. The failure zone in uniaxial tension was shown to be associated with large-scale fibre alignment, consistent with this being the major determinant of mechanical properties. Under uniaxial tension, elastic moduli and failure stresses are an order of magnitude lower than those obtained under biaxial tension, consistent with the fibre alignment mechanism which is not available under biaxial tension.

Cross-Linked Bacterial Cellulose Networks Using Glyoxalization

“…BC networks almost completely suppresses their stress-transfer efficiency. This effect has also been observed for cellulose whisker-based nanocomposites exposed to water 34 . This suggests that water has fully penetrated the BC networks, and therefore acts as a plasticizer, disrupting hydrogen bonding between fibrils, and consequently reducing local molecular deformation and therefore stress-transfer within the network.…”

“…This embrittlement may occur due the presence of cross-linking between BC layers, which will reduce layer-to-layer mobility, and consequently delamination. Cross-linking must also occur in the plane of the specimen, which could reduce orientation effects previously reported for BC networks 34 .…”

“…The Raman band initially located at 1095 cm -1 , highlighted in Figure 7a, has been extensively used for stress-transfer quantification in cellulose materials 1,17,15,34 . This band is thought to be representative of C-O ring stretching modes 35 and/or the C-O-C glycosidic bond stretching 36,37 .…”

Produção e degradação in vitro de estruturas tubulares de celulose bacteriana

“…George e colaboradores [18] relataram que em meio alcalino ocorre uma quebra do padrão de ligação de hidrogênio das microfibrilas de celulose. Quanto maior a concentração da solução de NaOH utilizada, maior o número de íons sódio que penetrarão na membrana, quebrando ligações de hidrogênio inter e intra moleculares entre as fibras de celulose adjacentes e, consequentemente, mais "afrouxado" ficará o arranjo estrutural da celulose, resultando em um inchamento da película [16,18,22] . A aparência dos vasos de celulose bacteriana após purificação é de hidrogéis translúcidos (Figura 3).…”

Bacterial Cellulose for Skin Repair Materials

“…As was expected, the elastic modulus and failure stress under uniaxial tension were one order of magnitude lower than the values obtained under biaxial tension, since a fibre alignment mechanism is not available under biaxial tension. BC behaves like a viscoelastic material, brittle failure being reached at approximately 20% strain and 1.5 MPa stress under uniaxial tension (McKenna et al, 2009). Compression pressure has been found to be an important parameter controlling the final mechanical properties of BC films: Slightly enhanced tensile strength and deformation at break were obtained by increasing the molding compression pressure, while the modulus also decreased nearly linearly with increasing film porosity.…”