L-asparaginase release from Escherichia coli cells with aqueous two-phase micellar systems

A method was proposed to release and separate L-asparaginase (EC 3.5.1.1) from Escherichia coli ATCC 11303 cells with aqueous two-phase micellar systems. The systems were composed of K2HPO4 and Triton X-100. The method combines enzyme release with enzyme purification. The influence of Triton X-100 concentration, K2HPO4 concentration, and pH on the release and partition of L-asparaginase was investigated. Experimental results showed that E. coli cells treated with 9.4% (w/v) K2HPO4 and 15% (w/v) Triton X-100 at 25 degrees C for 15-20 h released nearly 80% of the enzyme. Most of the released enzyme was partitioned to the bottom phase (phosphate-rich phase). The effects of Triton X-100 concentration, K2HPO4 concentration, and pH on cloud point were also studied. Electron micrography indicated that the chemical treatment altered the inner structure of E. coli cells significantly.