Improved Extracellular Level of L-Asparaginase in Shaken Cultures of Escherichia coli ATCC 11,303 Using a Statistical...

Direct purification of a protein from the culture medium is usually the simplest and most cost-effective method, so maximizing extracellular yield is one of the most important goals in protein supply. Although L-asparaginase is not naturally secreted into the extracellular medium through conventional cellular secretory pathways in Escherichia coli, some proteins were previously shown to be released from periplasm of E. coli into medium depending on culture medium and aeration efficiency. Here, extracellular release of L-asparaginase into the culture medium by the E. coli ATCC 11303 was demonstrated and found to be strongly dependent on medium composition, aeration effectiveness, and their interaction. Employing the RSM-CCD (response surface methodology- central composite design), the impacts of four independent factors (shaking speed, maltose, tryptone, and L-asparagine concentrations) on extracellular L-asparaginase activity were also investigated. Optimization of the culture medium led to a significant increase in extracellular L-asparaginase activity, closely matching the predicted values and confirming the robustness of the model. Although further studies appear necessary, this investigation highlights the practical importance of aeration and culture medium composition in extracellular release of L-asparaginase.