Then, 500 ml of isopropanol was added to 625 ml of the supernatant and incubated for at least 30 min at room temperature.
The pellet was collected from the solution by centrifugation at 15,000 rpm for 15 min and washed with 75% ethanol.
The pellet was dissolved in 200 ml of TE buffer (10 mM TriseCl and 1 mM EDTA, pH 8.3) and purified as described above.