Abstract
Polyhydroxyalkanoates (PHA) production and extraction of different bacterial strains isolated from contaminated urban and hilly areas was conducted. The 30 bacterial isolates were Gram negative and belonged to Pseudomonas, Citrobacter, Klebsiella, Escherichia and Enterobacter genera. Bacterial level of resistance against antibiotics (Penicillin) and heavy metals (zinc, cadmium and copper) was determined. Bacterial isolates from contaminated urban areas were found to be more resistant. The screening for PHA production was done by the Sudan black staining. Among the urban area isolates, U17, U8 and U9 produced highest concentration of PHA (50.4, 40.6 and 37.9%) while in hilly area isolates H8, H6 and H9 showed highest production (45.8, 42.4 and 37.6%) by SDS digestion method. The percentage production was lowered when the extraction was done by sodium hypochlorite digestion method. Selected bacterial strains were optimized for PHA production at different growth conditions that is, pH, temperature and carbon sources. Bacterial isolates U8, U17 and H8 produced maximum amount of PHA 74, 69 and 59%, respectively, at pH 7, 37°C and using cooking oil as carbon source after 72 h. PHA polymerase phaC1/C2 genes were successfully amplified from genomic DNA of three bacterial isolates showing 540 bp DNA fragment which confirmed the presence of phaC1/C2 gene presence. It showed that the corresponding bacterial isolates would have been able to synthesize medium chain length PHA.
Highlights
Polyhydroxyalkanoates (PHAs) are the environmentally friendly polyesters which can be accumulated to as much as 90% of cellular dry weight during unbalanced growth in the form of inclusion bodies in over 300 different microorganisms (Liu and Log, 2006)
Seventeen bacterial isolates were collected from contaminated urban areas and thirteen bacterial isolates were collected from contaminated hilly areas (Table 1)
Based on Gram stain’s results and biochemical reactions the PHA producing bacterial isolates belong to the genus Pseudomonas, Citrobacter, Klebsiella, Escherichia and Enterobacter
Summary
Polyhydroxyalkanoates (PHAs) are the environmentally friendly polyesters which can be accumulated to as much as 90% of cellular dry weight during unbalanced growth in the form of inclusion bodies in over 300 different microorganisms (Liu and Log, 2006). PhaC is essential for PHA synthase activity. Two forms of PHA synthase have been reported, an active form in PHA-accumulating cells and an inactive form in nonaccumulating cells, where PhaC is more susceptible to degradation (McCool and Cannon, 2001). More than 150 different hydroxyalkanoic acid derivatives have been identified as constituents of PHA (Yang et al, 2006). These PHA monomers can be synthesized in a variety of configurations to produce a wide range of material properties (Zhang et al, 2006)
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