An optimized ultrasonication protocol for bacterial cell disruption and recovery of β-galactosidase fusion proteins

In this work, we have developed and optimized an ultrasonication protocol for Escherichia coli recombinant cells, adapted to laboratory-scale release of β-galactosidase fusion proteins. After a single sonication treatment of 15 minutes, about 30% of recombinant protein present in the sample remains still associated to cellular debris, and it can not be removed by increasing the sonication time. After a clarification step a second sonication treatment of the resuspended cell debris again releases only a 70% of the remaining product. Therefore, the application of two short, consecutive sonication treatments permits a global recovery yield of about 90%. The use of a new disruption buffer to stabilize β-galactosidase allows the fusion proteins to maintain the active form throughout the process. © 1994 Science and Technology Letters.