L-arginine amidinohydrolase by a new Streptomyces isolate: Screening and statistical optimized production using response surface methodology

Abstract

Abstract l -arginine amidinohydrolase has been reported as a powerful anticancer agent due to its mediating l -arginine starvation. The aim of this study was to screen a pool of 30 actinomycetes belonging to the species Streptomyces in order to select the potent argininolytic one. Streptomyces strains isolated from soil were firstly functional screened based on their argininolytic capacities by a qualitative assay based on a pH indicator substrate (phenol red). The second screening was the quantitative evaluation of the l -arginine amidinohydrolase activity via a Ninhydrine assay. The measurement was performed on two different cell preparations, involving the extracellular compartment and the cell lysates extract. Among the tested isolates, a strain coded as MAM5 produced extracellular and intracellular l -arginase simultaneously under the same culture conditions. The isolate was identified as Streptomyces diastaticus MAM5 by phylogenetic analysis of the 16S rRNA sequence. Optimization and validation of different process parameters via Box-Behnken design were done for maximum production of extracellular and intracellular l -arginase. Collectively, culturing in shake flasks with the optimized medium resulted in a 4.5-fold and 3.5-fold increase in extra- and intracellular l -arginase production, respectively, when compared to screening medium. Additionally, l -arginase was partially purified using heat treatment and precipitation with cold ethanol, and the enzyme exhibiting 3.2-fold and 3.1-fold for extra- and intracellular form respectively, in comparison with the crude enzyme. Both forms of l -arginase had maximum activity in alkaline pH (8.5–9) at 40–50 °C with ionic stability within pH range 8–10 and thermal stability below 60 °C.