Optimization of l-methioninase and l-arginase production by newly isolated marine yeast using response surface methodology

Abstract

l-methioninase and l-arginase are important anticancer agents that are used extensively worldwide. In this study, fifteen marine yeast isolates were obtained from the marine environment of Red Sea and screened for l-methioninase and l-arginase production. A promising isolate, S5 was identified based on 18 S rRNA gene sequencing as Candida labiduridarumS5. Collectively, screening of different culture variables was achieved by Plakket-Burmn experimental design using Czapek Dox medium in order to determine the most significant parameters for l-methioninase and l-arginase production. With respect to the main effect of each variable, namely five independent factors, yeast extract, l-methionine, l-arginine, pH and incubation period had a significant effect on l-methioninase and l-arginase production by Candida labiduridarum. Subsequently, these significant parameters affecting enzymes production were optimized using the Box-Behnken and its representative four-factor response-surface method for each enzyme separately. These predicted conditions were verified by validation experiments and the optimal conditions for the highest l-methioninase production were l-methionine (3.4646 g/L), yeast extract (3.1414 g/L), pH (6.06) and for 38.6869 h. Meanwhile, the optimal conditions of l-arginase was l-arginine (3.5859 g/L), yeast extract (5.0808 g/L), pH (6.5758) and for 44.2805 h. The regression models demonstrated that the practical data could be suitably fitted into a first-order model with a significantly high (R2) value of more than 0.90 for all responses. The optimized process increased production of l-methioninase by 35.57 U/mg (2.2-fold) and l-arginase by 43.62 U/mg (4.9-fold), when compared to that obtained in the control medium. The total yield of the predicted l-methioninase and l-arginase was found to be near the practical result 32.8841 and 40.9934 U/mg respectively. Thus, this statistical approach enabled rapid identification and integration of key medium parameters for enhancing production of l-methioninase and l-arginase.