Abstract:
Polyhydroxyalkanoates (PHAs) are energy and carbon reserve materials stored in the
cytoplasm of certain bacteria under stress conditions. PHAs are regarded as
biodegradable, biocompatible and environment friendly bioplastics. This study was
aimed to isolate bioplastic producers from a variety of environmental samples of
Pakistan, grow them on different carbon sources and characterize the bioplastic thus
produced. A total of twenty five isolates were obtained from oil/diesel containing
soil, cafe waste water, municipal water, garden soil, and waste from paper pulp
industry. Out of them only three isolates showed black-blue colouration when
stained with Sudan black B, a preliminary screening agent for lipophilic compounds,
and positive result with Nile blue A staining, a more specific dye for PHA granules.
To confirm the genetic basis for PHA production PhaC gene (540 bp bands) was
amplified using specific primers. Moreover, 16S rRNA gene sequence analysis
confirmed the isolate with highest productivity as Pseudomonas putida DLL-E4.
PHA production over course of time was studied using three different carbon
sources i.e. glucose, sucrose and sunflower seed oil. Results indicated highest PHA
yield with glucose 10.4 mg/L at 60 hrs, sucrose yielded 9 mg/L at 40-60 hrs and
lowest yield 4 mg/L at 40 hrs was obtained with sunflower seed oil. Extracted
polymer was characterized by X- ray diffraction and FTIR analysis revealed
amorphous nature of PHA. Polymer was tested for pH stability was checked and
found to be stable at pH 3 for 3 minutes.
