Expressed bacterial cells were pelleted and 0.48 g of wet weight
cells obtained from 50 ml of culture was lysed in 6 ml of lysis buffer
(50 mM NaH2PO4, 300 mM NaCl, 10 mM Imidazole, pH 8.0).
Lysozyme lyophilized powder MW 14600 obtained from chicken
egg white (Himedia Cat. no. RM074) at a concentration of 1 mg/
ml was also added to the suspension. After 30 min on ice-bath,
the suspension was sonicated for 10 min at 40W amplitude and
8 s pulse. The sonicated sample was centrifuged at 10,000 rpm
for 30 min at 4 C. The soluble fraction of protein present in cleared
lysate was purified using Ni–NTA affinity chromatography. Small
fraction of cleared lysate and pellet after centrifugation was kept
for analysis in SDS–PAGE. The cleared lysate was loaded onto the
pre-equilibrated column with lysis buffer and the protein was allowed
to bind with resin for 10 min and the flow-through was collected.
Further the column was washed three times with wash
buffer (50 mM NaH2PO4, 300 mM NaCl, 20 mM imidazole, pH
8.0) to remove the unbound non-specific proteins and finally protein
was eluted from column using elution buffer (50 mM NaH2-
PO4, 300 mM NaCl, 250 mM imidazole, pH 8.0) in 3–4 fractions of
1 ml each. All the fractions of purified protein were analysed by
SDS–PAGE