Effects of exopolysaccharides from Escherichia coli ATCC 35860 on the mechanical properties of bacterial cellulose nanocomposites
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The effects of growing bacterial cellulose (BC) in the presence of exopolysaccharides (EPS) extracted from Escherichia coli ATCC 35860 on the mechanical properties of BC have been studied. After harvesting and purifying the EPS, its composition was analyzed by gas chromatography-mass spectrometry. When adding the purified EPS into the culture media, another kind of EPS, composed of fructose, was produced by Gluconacetobacter xylinus ATCC 23769 and a minor portion of the added EPS was incorporated into cellulose fibrillar network. The characteristics of BC nanocomposites synthesized in the presence of purified EPS was systematically studied through tensile testing, x-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The results revealed that the EPS affected the cellulose-cellulose interactions during the physical aggregation of crystalline microfibrils, but did not impact the co-crystallization process during BC synthesis. The addition of 4 or 8 mg/L purified EPS into the culture media, was found to significantly improve the mechanical properties of BC nanocomposites while maintaining BC crystallinity and crystal size.
KeywordsExopolysaccharides Biofilm Bacterial cellulose Ribbon assembly Crystallinity
The authors acknowledge Nichole Wonderling, Gino Tambourine, Bangzhi Liu, and Julie Anderson in Millennium Science Complex, Penn State, for their training and guiding on XRD, FTIR, and SEM. The authors also thank Dr. Philip Smith in the Huck Institutes of the Life Sciences, Penn State, for his help on GC-MS measurements.
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