Production of extracellular L-arginase by <i>Alcaligenes aquatilis</i> BC2 isolated from soda lakes (Lake Chitu) of Ethiopia

L-Arginase is a therapeutic enzyme that hydrolyzes L-arginine to ornithine and urea. The L-arginase extracted from bacteria has an anticancer activity by causing starvation of nutrients for cancer cells. This study aimed to screen and characterize L-arginase-producing bacteria and to optimize different factors influencing L-arginase production. Isolation and primary screening were carried out by using mineral arginine agar media using phenol red as an indicator. Molecular identification of the isolates was employed by using 16S ribosomal RNA sequencing and phylogenetic tree construction. L-Arginase assay by colorimetric method was carried out to measure the amount of urea liberated from the hydrolysis of L-arginine for quantitative screening. From 31 water samples, 102 colonies were isolated, and those colonies that convert the media to pink were selected as arginase-producing bacteria. 7 isolates were screened from qualitative screening method. Based on quantitative screening, the highest L-arginase was produced from bacteria Alcaligenes aquatilis BC2 (92.46 ± 0.19 U/ml) followed by Paenalcaligenes suwonensis BCW8 (59.29 ± 0.66 U/ml). Following their mean difference, isolate BC2 was selected for further optimization process of 8 parameters. After optimization, the isolate shows the maximum (163.85 U/ml) enzyme activity. The result of this study implies that novel bacteria were isolated from soda lakes that produce a considerable amount of L-arginase, which can be used as a promising anticancer activity. One-Sentence Summary: This study successfully isolated and characterized a novel L-arginase-producing bacterium, Alcaligenes aquatilis BC2, from Ethiopian soda lakes and optimized its enzyme production parameters for potential anticancer applications.