Abstract

Twelve polyhydroxyalkanoate (PHA) producing microbes were isolated from root nodules of 8 leguminous plants belonging to two phyla: Proteobacteria and Firmicutes. One of the isolate VK-12 of genus Burkholderia showed the highest PHA accumulation (42% wt/wt) as compared to other isolates in mineral medium. The effect of different cultural and growth conditions were studied on isolate VK-12 in shake flasks for highest PHA accumulation. VK-12 showed highest PHA accumulation in sucrose and ammonium sulphate amongst other carbon and nitrogen sources tested in the medium. The medium containing sucrose and ammonium sulphate having C: N ratio of 39.72 gave the highest PHA accumulation. The optimum pH, temperature, inoculum concentration and incubation time for highest PHA accumulation were 7.0, 30°C, 10% and 48 h respectively. An overall increase in PHA accumulation from 42 to 63% wt/wt was obtained under optimised conditions. The PHA was characterised using gas chromatography-mass spectrometry (GC-MS). All the isolates produced poly (3-hydroxybutyrate) (PHB) except VK-9, which produced polymer poly (3-hydroxybutyrate-co-3-hydroxyvalerate).

Key words: Polyhydroxyalkanoate (PHA), PHB-co-HV, root nodule bacteria, carbon sources, C: N ratio, characterization of PHA.

Abbreviation

Abbreviations: PHA, Polyhydroxyalkanoate; GC-MS, gas chromatography-mass spectrometry; PHB, poly (3-hydroxybutyrate).