Isolation and identification of L-asparaginase-producing endophytic fungi from the Asteraceae family plant species of Iran

L-asparaginase is an important anticancer enzyme that is used in the first line treatment of acute lymphoblastic leukemia. This study was conducted to isolate L-asparaginase-producing endophytic fungi from medicinal plants of family Asteraceae. Seven healthy medicinal plants from family Asteraceae were selected for the isolation of endophytic fungi using standard surface sterilization techniques. A total of 837 isolates belonging to 84 species were comprised of the stem (55.6%), leaf (31.1%), root (10.6%) and flower (2.7%). Initial screening of L-asparaginase-producing endophytes was performed by qualitative plate assay on modified Czapex dox's agar medium. L-asparaginase activity of fungal endophytes was quantified by the nesslerization method. Identification of endophytic fungi was performed using both morphological characteristics and phylogenetic analyses of DNA sequence data including ribosomal DNA regions of ITS (Internal transcribed spacer) and LSU (partial large subunit rDNA), TEF1 (Translation Elongation Factor) and TUB (β-tubulin). Of the 84 isolates, 38 were able to produce L-asparaginase and their L-asparaginase activities were between 0.019 and 0.492 unit/mL with Fusarium proliferatum being the most potent. L-asparaginase-producing endophytes were identified as species of Plectosphaerella, Fusarium, Stemphylium, Septoria, Alternaria, Didymella, Phoma, Chaetosphaeronema, Sarocladium, Nemania, Epicoccum, Ulocladium and Cladosporium. This study showed that endophytic fungi from Asteraceae members have a high L-asparaginase-producing potential and they can be used as an alternative source for production of anticancer enzymes.