Screening of bacteria for PHA production using waste glycerol as carbon source and the ability of new strain to produce P(3HB-co-3HV) copolymer

ABSTRACT

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.