Isolation of bacteria producing polyhydroxyalkanoates (PHA) from municipal sewage sludge |
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Authors: | S Vishnuvardhan Reddy M Thirumala T V Kishore Reddy S K Mahmood |
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Institution: | (1) Environmental Microbiology Lab, Department of Botany, Osmania University, Hyderabad, 500007, Andhra Pradesh, India |
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Abstract: | Bacterial isolates from sludge samples collected at a local municipal sewage treatment plant were screened for bacteria producing
polyhydroxyalkanoates (PHA). Initially Sudan black B staining was performed to detect lipid cellular inclusions. Lipid-positive
isolates were then grown in a nitrogen limitation E2 medium containing 2% (w/v) glucose to promote accumulation of PHA before
the subsequent staining with Nile blue A. The positive isolates were quantified initially with a u.v. spectrophotometer, for
a very large number of isolates (105) and among them high PHA-producing isolates (15) were selected and were confirmed by
gas chromatographic analysis. The GC analysis showed the polymers produced by 13 of the selected isolates to be polyhydroxybutyrate
(PHB), and the remaining two isolates produced polyhydroxybutyrate-co-hydroxyvalerate (PHB-co-HV) copolymer. The proportion
of the PHA-positive bacterial isolates showed variability in the number of PHA accumulators during various months. The correlation
of PHB production with the cell dry weight (CDW) was found to be statistically significant. The metabolism of PHB in these
selected 15 isolates was studied using the Nile blue A staining, which showed an initial increase in the fluorescence followed
by a decline, on further incubation. All the selected 15 isolates were classified to genus level by studying their morphological
and biochemical characteristics. There were seven Bacillus species, three Pseudomonas species, two Alcaligenes species, two Aeromonas species, and one Chromobacterium species. |
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Keywords: | Bacteria Municipal sewage sludge STP Isolation PHA Screening |
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