Mechanical properties of bacterial cellulose synthesised by diverse strains of the genus Komagataeibacter

Abstract

19Bacterial cellulose (BC) has several current and potential future uses in the food 20 industry because of its ability to form hydrogels with distinctive properties. The texture of 21 BC hydrogels is determined by both the cellulose fibre network and the internal dispersed 22 water. In this study, mechanical properties of hydrated BC synthesised by six different strains 23 of Komagataeibacter genus were investigated with regards to their extensibility, compressive 24 strength, relaxation ability, viscoelasticity and poroelasticity. The stress/strain at failure and 25 Young's modulus were assessed by uniaxial tensile testing. The compressive strength, 26 relaxation ability and viscoelasticity were measured via a series of compression and small 27 amplitude oscillatory shear steps. A poroelastic constitutive modelling simulation was used to 28 investigate the mechanical effects of water movement. The morphology of the BC fibril 29 network under compression was observed via scanning electron microscopy. Results showed 30 that the mechanics of BC were highly dependent on the cellulose concentration, as well as the 31 morphology of the fibril network. BC synthesised by ATCC 53524 was the most 32 concentrated (0.71 wt%), and exhibited high tensile properties, stiffness and storage moduli; 33 whereas the comparatively low mechanical properties were noted for BC produced by ATCC 34 700178 and ATCC 10245, which contained the lowest cellulose concentration (0.18 wt%).35 Small deformation responses (normal stress, G') scaled with cellulose concentration for all 36 samples, whereas larger deformation responses (Young's modulus, poroelasticity) depended 37 on both cellulose concentration and additional factors, presumably related to network 38 morphology. Increasing concentration and compressive coalescence of fibres in the integrated 39 BC network reduced both the relaxation of the normal stress and the movement of water. This 40 research aids the selection of bacterial strains to modulate the texture and mechanical 41 properties of hydrated BC-based food systems. 42 43 44 45 Keywords bacterial cellulose hydrogel; tensile test; compression test; small amplitude 46 oscillatory rheology; poroelasticity 47 Food gels based on cellulose, like Nata-de-coco, are valued for their juicy mouthfeel and 51 chewable texture (Zhang et al., 2017). The Nata-de-coco is derived from fermentation of 52 certain bacterial strains which produces ultra-fine fibres of bacterial cellulose (BC) in the 53 form of a hydrogel. BC hydrogels are characterised by a randomly oriented three-dimensional 54 swollen fibril network (typically above 99 wt% water). The chemical structure of BC is 55 identical to plant cellulose, i.e. β-1-4-linked glucan chains. These chains are arranged into 56 relatively crystalline BC fibres (also called ribbons), containing a large amount of hydroxyl 57 groups on their surfaces. Recent X-ray and neutron scattering analyses suggest that BC fibres 58 have a core-shell structure built up from microfibril units of ca. 3.4 nm di...

pH-Controlled Self-Assembled Fibrillar Network Hydrogels: Evidence of Kinetic Control of the Mechanical Properties

“…This experimental 0 ( ) behavior is in a good agreement with scaling laws of entangled polymers in a good solvent and in a semidilute regime with = 2.25, 63 or with = 11/5, for entangled semiflexible biopolymers. 66 Similar values are also found for fibrillary hydrogels composed of bacterial cellulose 67 and LMWG, 2,18,41,67 but one should also mention that = 5/2 66 The normalization of the strain sweep data (Figure S 2g) highlights the strain overshoot nature of SLC18:0 samples. 68 Such strain hardening overshoot was previously reported for a wide range of complex fluids like concentrated emulsions 69 or microgels suspensions, 70 but also for SAFIN without discussing its origin.…”

Bacterial Cellulose as a Raw Material for Food and Food Packaging Applications

“…Compared with other genera, Komagataeibacter is usually the genus of choice for research and food applications, due to its higher BC yield and purity (Ruka et al, 2012). Membranes with different network structure and mechanical properties were reported to be obtained from different strains of the genus Komagataeibacter (Chen et al, 2018).…”

Production and evaluation of biosynthesized cellulose tubes as promising nerve guides for spinal cord injury treatment

“…There was, however, no particular trend for the Young's modulus among the samples; the Young's modulus was approximately 1.6 MPa for all BCTs. It should be noted that structural variations in BC microstructures makes it difficult to directly correlate the Young's modulus among samples, as has also been observed by Bodin et al () and Chen, Lopez‐Sanchez, Wang, Mikkelsen, and Gidley (). BCT22 demonstrated a Young's modulus of 1.24 ± 0.07 MPa (Figure b), matching the Young's modulus of human spinal cord (i.e., 0.2 to 1.9 MPa; Bilston & Thibault, ; Dalton, Flynn, & Shoichet, ; Nagel et al, ).…”