Polyhydroxybutyrate (PHB) production by Halomonas elongata BK AG 18 indigenous from salty mud crater at central Java Indonesia

Abstract

Aims: Bioplastic is a biodegradable polymer produced by particular microorganism as a secondary metabolite. Some halophilic bacteria belonging to Halomonas genus have been reported to be a potential of polyhydroxybutyrate (PHB) producer. This study aims to explore the potential of an indigenous halophilic bacterial isolate, H. elongata BK-AG18, as bioplastic producer. The indication as bioplastics producer was evaluated by growing in nile red-containing medium and bacterial colonies displayed bright orange fluorescent under ultraviolet light. Methodology and results: Bioplastic production by H. elongata BK-AG 18 was achieved using modified glucosecontained High Medium (HM) after incubated in a rotary shaker for 22 h, 37 °C, 150 rpm. The bioplastic was extracted with chloroform and sodium hypochlorite (1:1) and precipitated in methanol. The highest yield of bioplastic production was 21.36% of the dried bacterial cell weight. The structural characterizations of the bioplastics using Fourier transformed infrared (FTIR), 1H and 13C nuclear magnetic resonances (NMR) spectroscopies showed high similarity to the spectral pattern of polyhydroxybutyrate (PHB). Further characterization using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed that the decomposition and melting temperature at 266 °C and 166.5 °C of the PHB, respectively. The result of PHB has a low degree of crystallinity (9.5%) that close to the rubber-like polymer. Conclusion, significance and impact of study: This study revealed the high potential of H. elongata BK-AG 18 as PHB producer with high mechanical properties.