2.4.1. Extraction and estimation of PHA
Extraction and estimation of PHA was performed based on the
procedure reported elsewhere (Venkata Mohan et al., 2010). The
biocatalyst was separated from the substrate by centrifugation
(3000g for 30 min at 10 C) and the resulting pellet was washed
with acetone and ethanol separately to remove unwanted materials.
The pellet was suspended in an equal volume of 4% sodium
hypochlorite and incubated at room temperature for 3 h. The
resulting mixture was centrifuged (3000g for 30 min at 10 C)
and the supernatant was discarded. The pellet with lysed cells after
washing simultaneously with acetone and ethanol was dissolved in
hot chloroform and passed through glass fiber filter (0.45 lm pore
size) to separate the polymer from cell debris. The chloroform filtrate
was used to estimate PHA colorimetrically. For the assay,
PHA polymer extracted in chloroform was subjected to evaporation
followed by addition of 10 ml of sulfuric acid (36 N) and
heated at 100 C on a water bath for 10 min. Addition of sulfuric
acid converts the polymer to crotonic acid. The cooled solution
was measured for the absorbance at 235 and 285 nm for determining
the poly (3-hydroxy) butyrate (PHB) and poly (3-hydroxy) valerate
(PHV) concentration, respectively against a sulfuric acid
blank. The standard curve was prepared using pure poly-3(hydroxy
butyrate-co-hydroxy valerate) [P3(HB-co-HV)] (co-ploymer; natural
origin, Aldrich). PHA in the extracted sample was confirmed
by FTIR and 1
H NMR spectroscopy.
2