Determination of protein concentration of crude
enzyme samples:
Protein concentration was determined using
Bovine serum albumin (BSA) as standard by using
Bradford reagent. Different concentrations of BSA
were prepared. The volume was made up to 3 ml using
distilled water; 1 ml of Bradford reagent was added to
each test tube and mixed well. After 30 min of
incubation, the absorbance was measured at 595 nm
by spectrophotometer and the protein content
determined. The crude enzyme samples were
processed in a similar manner as described above.
Purification of L-asparaginase:
Purification of intracellular L-asparaginase of
E. coli VRY-15 was done using gel permeation column
chromatography using Sephadex G-100 and its purity
was checked using SDS PAGE. Sodium dodecyl sulfate
polyacrylamide gel electrophoresis was carried out in
using slab gel of 7% acrylamide in a Tris-HCl buffer
pH 8.3 containing 0.1% SDS. The gels were stained
with 0.025 Coomassie brilliant blue R-250 and destained
(Stegemann, 1979).
Results:
A total of 35 bacterial strains were isolated
from 14 different sewage samples (Table I). All the
isolated bacterial cultures were found to be Gramnegative.
Their shape varied from bacillus to coccobacillus.
They all were found to be motile and possessed
green metallic sheen when inoculated on EMB agar
plates. Lactose fermentation along with production of
acid and gas was observed with all the isolates. They
Table I: Isolation of bacterial cultures from sewage water
samples
Fig. Ia: Agar diffusion test for L-asparaginase activity in E. coli
VRY-15.
showed a positive response to indole test and methyl
red test and negative response to VP and citrate
utilization test. Results of morphological and
biochemical studies showed that the isolates belong to
the genus Escherichia.
Asparaginase activity varied upto great extent
among different isolates. Maximum activity of
intracellular L-asparaginase was recorded in E. coli
VRY-15 showing 2.0 cm zone of enzyme activity (Fig.
Ia & Ib)