Release of beta-lactamase from transformed E. coli cells by homogenization, osmotic shock, and various chemicals made in 200 mM Tris buffer pH 7.5. Results are averages of two measurements. The yield factor was calculated by dividing target protein yield by total protein yield. Target protein yield and total protein yield are relative to the extraction by osmotic shock; the amounts of target and total proteins recovered from the bacterial cells by osmotic shock were considered as 100 % target and total protein yields, respectively