Aims: This study is focused on the isolation, characterization and screening of new bacterial strains isolated from soil and wastewater samples that are able to produce PHA utilizing waste glycerol as sole carbon source in order to create useful products from waste glycerol and at the same time reduce the PHA production cost. A new isolate, Burkholderia contaminans Kad1 strain was investigated for its ability to biosynthesize PHA copolymers containing 3HV monomers from waste glycerol and 3-hydroxyvalerate (3HV) precursors. Methodology and results: PHA producing bacteria were screened using Nile Red and 1% of Nile Blue method. The presence of PHA granules was detected using phase contrast and fluorescence microscopy. Burkholderia contaminans Kad1, one out of 23 positive samples, was selected for further study because of its ability to produce high PHA content (47 wt%) and dry cell weight (DCW), (4.2 g/L) when waste glycerol 2% (v/v) was used as the sole carbon source. The 16S rDNA and the PHA synthase gene were sequenced and the PHA produced was confirmed by NMR analysis. A mixture of waste glycerol and sodium valerate fed to the culture gave rise to poly(3-hydroxybutyrate-co-3- hydroxyvalerate) [P(3HB-co-3HV)]. The mole fraction of 3HV monomer in the co-polymer P(3HB-co-3HV) sample analyzed using 1H NMR was 23 mol%. Conclusion, significance and impact of study: This study demonstrated for the first time B. contaminans Kad1 was able to use waste glycerol for PHA biosynthesis including the P(3HB-co-3HV) copolymer using a mixture of waste glycerol with sodium valerate as the precursor.
bacteria

Aims:This study was carried out to optimize the fermentation conditions using statistical approach for polyhydroxyalkanoate(PHA) production by a local isolate, Burkholderia cepaciaBPT1213, in the shake flask system.Methodology and results:Throughout this study, B. cepaciaBPT1213 was grown in minimal salt medium (MSM) supplemented with 2% of waste glycerol (86.70% purity).The strain can produce up to 1.33 g/L cell dry weight (CDW) with 22.21% of PHA content, thus giving a total PHA concentration 0.30 g/L before optimization. A factorial design experiment that was carried out showed all parameters KH2PO4, Na2HPO4·2H2O, carbon-to-nitrogen ratio (C/N), initial pH of medium, and temperature significantly affected the growth (cell dry weight, CDW) and PHA content. Response surface methodology (RSM) using central composite design (CCD) was then applied to optimize these parameters. The optimum conditions suggested were at 2.5 g/L KH2PO4, 4.5 g/L Na2HPO4·2H2O, 30 (g/g) C/N ratio, initial medium pH of 8.5 and 37 °C cultivation temperature, with a predicted CDW of 3.43 g/L and PHA content of 45.71% contributing to 1.57 g/L total PHA concentration. The verification experiment resulted in 3.60 g/L of CDW with 48.08% of PHA content contributing to 1.73 g/L total PHA concentration.Conclusion, significance and impact of study:The statistical approach using factorial design and RSM have succeeded in increasing the production of PHA by B. cepaciaBPT1213 using waste glycerol as the sole carbon source which is a promising renewable and cheaper feedsto