Production and optimization of polyhydroxyalkanoates (PHAs) from Paraburkholderia sp. PFN 29 under submerged fermentation

Abstract

Background: Polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV) are the most common polyhydroxyalkanoates (PHAs). They are important candidates for biodegradable plastics that accumulate in the cytoplasm in the form of intracellular granules under unbalanced growth conditions. The present study focused on the production and optimization of PHAs from Paraburkholderia sp. PFN29 for the first time under submerged fermentation.

Results: Two hundred bacterial isolates were collected from soil samples in Thailand, six of which were found to accumulate PHB using the Nile red staining method. Six isolates were identified by 16S rDNA gene sequencing and were shown to be closely related to the genera Azotobacter, Sphingobium and Paraburkholderia. The best strain, Paraburkholderia sp. PFN29, showed the highest PHB concentration (5 ± 0.17 g/L). Optimization of PHB accumulation was achieved in modified medium containing 3% (w/v) glucose, and 0.1% (w/v) (NH4)2Fe(SO4) with incubation at pH 7.0 and 35°C for 96 h with shaking at 200 rpm. In preliminary PHBV synthesis, PFN29 was utilized to synthesize PHBV from glucose and organic acids (levulinic acid and propionic acid). 1H nuclear magnetic resonance (1H NMR) spectroscopy and gas chromatography-mass spectrometry (GC/MS) analyses confirmed the extracted PHAs compared to standard PHB and PHBV.

Conclusions: PFN29 can be used for feasible PHB production with a PHB content of up to 97.3% of 5.14 ± 0.17 g/L CDW. The PHBV concentration can be further improved by optimizing the production parameters as cosubstrates. The present study provides useful data on PHA production by Paraburkholderia, which may be used as a candidate species for commercial PHA production.