The diverse applications of L-asparaginase have led us to explore new sources of this enzyme. Arthrospira platensis has been scarcely reported as a new candidate for L-asparaginase production. In the present study, we localized L-asparaginase in A. platensis and enhanced its production. Enzyme localization was conducted by culturing cells in SOT medium and extracting the enzymes from different parts of the cell. The Taguchi method (factors studied: nitrogen, iron, sodium chloride, and temperature shock) using an L9 orthogonal array was designed for improving L-asparaginase production. The highest specific activity of L-asparaginase was found in subcellular, cytoplasmic extracts (0.166 ± 0.029 U/mg). Optimization data revealed that the highest production of L-asparaginase (0.275 ± 0.005 U) was attained by NaNO3, NaCl, and FeSO4·7H2O at concentrations, 1.875 g/l, 0.25 M, and 0.0075 g/l, respectively, with 1-h temperature shock at 22 °C in the dark. Results revealed more than twofold higher production of L-asparaginase than that under the normal condition. In summary, L-asparaginase appeared dominantly in the cytoplasmic region and its production could be induced by employing combined stress conditions with a Taguchi experimental design. To our best knowledge, this is the first report on L-asparaginase production in cyanobacteria of the subclass Oscillatoriophycideae.
Keywords: Arthrospira platensis; Asparaginase; Localization; Production; Stress.