Structure and Morphology of Microbial Degraded Poly(ε-caprolactone)/Graphite Oxide Composite
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Biodegradation of poly(ε-caprolactone) composite with graphite oxide (GO) by the action of Bacillus subtilis (BS) was studied in this work. Nanocomposite produced in a form of thin film was exposed to nutrient cultivation medium with BS as well as to abiotic nutrient medium (control run) at 30 °C. The matrix itself was exposed to the same conditions for comparison. Biodegradation was demonstrated by the weight loss and the decrease of molecular weight during 21 days of the experiment as well as by changes in the surface morphology and structure. Both degraded and control materials were characterized by confocal laser scanning microscopy, differential scanning calorimetry, thermogravimetry, and Fourier transform infrared spectroscopy with attenuated total reflectance. The bacterial growth expressed as the measure of the optical density/turbidity in McFarland units and pH of medium were measured in situ during the experiment. Lipolytic activity of BS was determined by spectrophotometric assay. Degradation process was accompanied by the increase of matrix crystallinity degree. GO served as nucleating agent and facilitated absorption of cultivation media into the composite which led to the increase of the crystallinity degree also for control nanocomposite specimens. It was not evaluated to be promoter of biodegradation. The surface cracks formation was initiated by BS action. Large surface cracks were formed on BS-degraded composite surfaces while surface erosion was more significant on BS-degraded matrix.
KeywordsPoly(ε-caprolactone) Graphite oxide Biodegradation Lipase Structure
R.B., L.R., J.J. were supported by the project “CEITEC—Central European Institute of Technology” (CZ.1.05/1.1.00/02.0068) from European Regional Development Fund, by the project MATERIS—CZ.1.07/2.3.00/20.0029 from European Social Fund. J.O, S.V., P.D. were supported by specific research (FCH-S-13-1912) from the Ministry of Education, Youth and Sports of Czech Republic. S.H. would like to thank Dr. Jan Merna from Institute of Chemical Technology, Prague, Faculty of Chemical Technology, CZ for SEC analysis. Authors thank Dr. Jiří Másilko from Materials Research Centre, Faculty of Chemistry, Brno University of Technology, CZ for X-ray diffraction analysis and Karbotechnik, Ltd, the CZ for graphite.
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