A research team at McMaster University has used microfiltration to purify a recombinant elastin-like fusion protein. The group fused an elastin-like polypeptide (ELP) to a target protein, thioredoxin. By increasing the temperature or salt concentration, the fusion protein formed micrometer-sized aggregates. A microfiltration membrane retained the aggregates but allowed the contaminating proteins from the lysate of Escherichia coli host cells to pass through when the filter was washed. Passing Milli-Q ultrapure water through the retained material on the membrane eluted pure, active protein.