Bacterial cellulose mechanical properties

Orts et al. [17] investigated composites of wheat or potato starch blended with pectin and reinforced with cellulose nanofibrils extracted from cotton, softwood, or bacterial cellulose. Mechanical and thermal properties of composites produced by casting and extrusion (extruded under a low and high shear mode) were evaluated. The addition of cellulose microfibrils to starch had a significant effect on mechanical properties at low concentrations. For example. Young s modulus of wheat starch nanocomposites reinforced with cotton nanofibrils increased by five times with the addition of only 2.1 wt% of nanofibrils (see Table 11.1). 

Bacterial cellulose has several unique properties that potentially make it a valuable material for the development of PEM fuel cells (Reference 1) (1) it is an inexpensive and non-toxic natural resource (2) it has good chemical and mechanical stability (3) it is very hydrophilic and (4) it doesn t re-swell after drying. Additionally, its thermal stability and gas crossover characteristics are superior to Nation 117 , a material currently widely used as a proton conductive membrane in PEM fuel cells. 

The strengths of the resulting dried sheets were tested by applying mechanical compression forces to determine the relative effects of the bacterial strains. As shown (Table 2), there were no significant differences between the textures of all bacterial cellulose strength levels derived from the three strains. Both coconut and pineapple juices yielded the same strength rating. The mechanical properties of bacterial cellulose, both air-dried and hot-pressed... 

This study showed that the bacterial cellulose derived fix)m coconut and pineapple juices can be converted efficiently to bacterial cellulose by the supplementation of yeast extract and ethanol under static fermentation conditions at 30 °C. Bacterial celluloses produced from all strains are growth associated products. Coconut juice seems to be a better substrate than pineapple juice. In view of energy consumption, the productivity of BC on this medium is high, which makes the production costs lower than expected. It is also clear that different A. xylinum strains produce different BC content levels under the same inoculation volumes and under static cultivation conditions. These results suggest that bacterial cellulose pellicles of all strains appear to be easily applied to use in many applications such as food, paper, and textile industries, without requiring additional steps of decolorization and purification. Furthermore, the properties of cellulose, in tenns of crystallinity, high water-absorption capacity, and mechanical strength of the reported strains, have additional applications in cosmetics and medicine. 

Backdahl, H., Helenius, G., Bodin, A., Nannmark, U., Johansson, B. R., Risberg, B., and Gatenholm, P. (2006). Mechanical properties of bacterial cellulose and interactions with smooth muscle cells,... 

Nge, T. T., Nogi, M., Yano, H., and Sugiyama, J. (2010). Microstructure and mechanical properties of bacterial cellulose/chitosan porous scaffold, QslMSS f 349-363. 

Nanocellulose, such as that produced by the bacteria Gluconacetobacter xylinus (bacterial cellulose, BC), is an emerging biomaterial with great potential in several applications. The performance of bacterial cellulose stems from its high purity, ultra-fine network structure and high mechanical properties in the dry state [114]. These features allow its applications in scaffold for tissue regeneration, medical applications and nanocomposites. A few researchers have used bacterial cellulose mats to reinforce polymeric matrices and scaffolds with wound healing properties [115-121]. BC is pure cellulose made by bacterial fabrication via biochemical... 

In this chapter we have reviewed some of the most important characteristics of cellulose and cellulose based blends, composites and nanocomposites. The intrinsic properties of cellulose such as its remarkable mechanical properties have promoted its use as a reinforcement material for different composites. It has been showed that cellulose is a material with a defined hierarchy that tends to form fibrillar elements such as elementary fibrils, micro fibrils, and macro fibers. Physical and chemical processes allow us to obtain different scale cellulose reinforcements. Macro fibers, such as lignocellulosic fibers of sisal, jute, cabuya, etc. are used for the production of composites, whereas nano-sized fibers, such as whiskers or bacterial cellulose fibers are used to produce nanocomposites. Given that cellulose can be used to obtain macro- and nano-reinforcements, it can be used as raw material for the production of several composites and nanocomposites with many different applications. The understanding of the characteristics and properties of cellulose is important for the development of novel composites and nanocomposites with new applications. 

Recently, bacterial cellulose, produced by Acetobacter Xylinum, was used as reinforcement in composite materials with a starch thermoplastic matrix [230]. The composites prepared with bacterial cellulose displayed better mechanical properties than those with vegetable cellulose fibers. 

Dammstrdm, S., Salmdn, L., Gatenholm, P. The effect of moisture on the dynamical mechanical properties of bacterial cellulose/glucuronoxylan nano composites. Polymer 46, 10364-10371 (2005)... 

Although chemically identical to plant cellulose, the cellulose synthesized by bacterial has a fibrillar nanostructure which determines its physical and mechanical properties, characteristics which are necessary for modem medicine and biomedical research [2, 3]. In this book chapter, the structural features of microbial cellulose and its properties are discussed in relation to the current and future of its application in medicine. 

Jung, R., Jin, H.-J. Preparations of silk fibroin/bacterial cellulose composite films and their mechanical properties. Key Eng. Mater. 342-343, 741-744 (2007)... 

Scionti, G., 2010. Mechanical Properties of Bacterial Cellulose Implants. Chalmers Tech. University, Goteborg. 

Yamanaka, S., Watanabe, K., Kitamura, N., Iguchi, M., Mitsuhashi, S., Nishi, Y., et al., 1989. The structure and mechanical properties of sheets prepared from bacterial cellulose. J. Mater. Sci. 24, 3141-3145. 

---