Biosynthesis and Characterization of Bioplastic Polyhydroxybutyrate from Halophilic Bacterium Halomonas elongata BK-AB8

摘要

Bioplastics are biodegradable polymers which can be produced by bacteria. The production occurs when the bacteria grow in a medium containing a minimum amount of key nutrients, such as nitrogen, magnesium, and phosphorus but is rich of carbon source. It is known that some bacteria from the genus Halomonas can produce bioplastics compound such as polyhydroxybutyrate (PHB). This study focused to evaluate the potential of Halomonas elongata BK-AB8 in producing PHB. The bacteria were grown on a medium containing nile red. The grown bacterial colony exhibited orange luminescence when exposed under UV light indicating that the bacteria was able to produce bioplastics. The bioplastic production was conducted by growing the bacteria in the modified growth medium at 37 °C for 22 hours with an aeration rate of 150 rpm. The resulting bioplastic was extracted using a mixture of chloroform-NaOCl (1:1), and subsequently precipitated in methanol. The highest efficiency of bioplastics production by Halomonas elongata BK-AB8 was around 24.7% using glucose as the main carbon source. 'H-NMR, ~(13)C-NMR, and FTIR characterizations of the resulting bioplastic showed high similarities to the corresponding profiles of PHB, which is likely in the form of poly-(R)-hydroxybutyrate. Thermogravimetry Analysis (TGA) showed that the resulting PHB sample started to degrade at 210 °C. Further characterization by Differential Scanning Calorimetry (DSC) showed a melting temperature of PHB at 164 °C with a degree of crystallinity around 14.2%, which strongly indicates that PHB was successfully produced from Halomonas elongata BK-AB8.