| Abstract [eng] |
The aim of this study was to evaluate the influence of different carbon sources on the synthesis, yield and properties of polyhydroxyalkanoates. The synthesis of polyhydroxyalkanoates was carried out using three bacterial cultures, Bacillus subtilis, Cupriavidus necator and Escherichia coli. The carbon sources chosen for the study were cane sugar, glucose, molasses, treated molasses, sucrose and stevia. After evaluation of all the yields of polyhydroxyalkanoates, it was found that the highest concentration of polyhydroxyalkanoates was obtained from the culture of Bacillus subtilis after a 48-hour fermentation with cane sugar as the carbon source in the fermentation medium (8,03 g/l). After the biosynthesis of polyhydroxyalkanoates of these microorganisms with each carbon source, the properties of the synthesised compounds were investigated. The structure of the polyhydroxyalkanoates produced in the study was evaluated by FTIR spectroscopy. DPPH, FRAP, ABTS radical scavenging assays and reductive property assay were carried out in order to elucidate the antioxidant activity of the compounds. The polyhydroxyalkanoates produced from Escherichia coli with stevia as the carbon source (0.17 o.v.) were found to have the highest reductive properties. The biopolymers obtained from Cupriavidus necator with cane sugar as the carbon source had the highest reducing properties according to the FRAP method (0,0023 µmol/l). The most effective inhibitor of the ABTS radical was the polyhydroxyalkanoates obtained from Bacillus subtilis culture with glucose as the carbon source (99,5 %). |
