Maximization of uricase production in a column bioreactor through RSM based optimization.

Uricase (EC 1.7.3.3) is an oxidoreductase enzyme which is widely exploited for diagnostic and treatment purposes in medicine. This study has been focused on producing recombinant uricase from E. coli BL21 in a bubble column bioreactor (BCB) and finding the optimal conditions for maximum uricase activity. The three most effective variables on uricase activity were selected through Plackett-Burman design from 8 different variables and were further optimized by central composite design of RSM. The selected variables included the inoculum size (%v/v), IPTG (Isopropyl β-d-1-thiogalactopyranoside) concentration (mM) and the initial pH of culture medium. The activity of uricase, final OD600 (Optical Density at 600nm wave-length) and final pH were considered as the responses of this optimization and were modeled. As a result, the activity of 5.84 U.ml-1 and final OD600 of 3.42 were obtained at optimum conditions of 3 %v/v of inoculum size, IPTG concentration of 0.54 mM and pH=6.0. By purifying the obtained enzyme using a Ni-NTA agarose affinity chromatography column, 165±1.5 mg uricase was obtained from a 600 mL cell culture. The results of this study show that bubble column bioreactors can be a highly effective option for large scale uricase production.