Screening of L-asparaginase-producing endophytic bacteria from mangrove Rhizophora mucronata

Abstract

L-asparaginase is an enzyme that converts L-asparagine to L-aspartate and ammonia. L-asparaginase is recommended as medical treatment of Acute Lymphoblastic Leukemia (ALL) and other malignant cancers. Bacteria are the most effective source of L-asparaginase as they can easily be cultured so that the enzyme can be extracted and purified. The commercial L-asparaginase is now available from bacterial but has many side effects for the patients. Therefore, the alternative source of this enzyme is highly necessary to be explored for a more effective and safer future production of L-asparaginase. For this reason, this study was carried out to investigate the endophytic bacteria producing L-asparaginase from mangrove Rhizophora mucronata. The samples of the mangrove plants, i.e., roots, stems, and leaves, were surface sterilized with alcohol and sodium hypochlorite. Endophytic bacteria were screened for L-asparaginase production using the rapid plate assay on Minimal Salt Medium with L-Asparagine as a substrate. Asparaginase-producing endophytes were detected by a pink zone formation on the agar, indicating the hydrolysis of asparagine into aspartic acid and ammonia, which changed the phenol red dye indicator from yellow (acidic conditions) to pink (alkaline conditions). The results revealed that out of the mangroves taken from the seaside, i.e., between sea and land, there were six bacterial colonies from the roots, 12 bacterial colonies from the stems, and 20 bacterial colonies from the leaves, each showing positive L-asparaginase. The isolated bacteria had varied colony morphology and different ability to produce the L-asparaginase enzyme.