Isolation and characterization of a bacterium with free glutaminase L-Asparaginase II from the Persian Gulf

L-asparaginase enzyme has various applications, particularly in medicine and food industry. Given some side effects and adverse possession of a minor amount of glutaminase activity, the search for new sources of microbes producing glutaminase-free L-asparaginase type II is underway. The present study aimed to isolate a bacterium from the Persian Gulf that produces glutaminase-free L-asparaginase type II. It is also aimed to measure the amount of this enzyme and the condition under which it increases. In order to assess the capability of extracellular asparagine production, the isolated bacteria from the seawater were cultured in M9 medium containing phenol red and asparagine. Those bacteria with positive asparaginase test were cultured in M9 medium containing glutamine and phenol red to assess their glutamine activity. The bacterium isolate producing asparaginase was identified using morphological and biochemical means and 16 SrDNA. L-asparaginase enzyme activity of the isolate was explored with a colorimetric method. The effect of anaerobic condition on the amount of L-asparaginase type II activity was explored by culturing under aeration condition and with no aeration. The result showed that the isolated bacterium was Rhizobium nepotum strain SHN1. The asparaginase enzyme activity and the specific activity of this bacterium were 0.467 IU/mL and 0.015 IU/mg, respectively. These characteristics increased to more than 50% in anaerobic condition. The results indicated that microbial flora from the Persian Gulf flora could be a remarkable source of glutaminase-free L-asparaginase enzyme.