Bioprocessing and purification of extracellular L-asparaginase produced by endophytic Colletotrichum gloeosporioides and its anticancer activity

L-asparaginase is an enzyme commonly used to treat acute lymphoblastic leukemia. Commercialized bacterial L-asparaginase has been reported to cause several life-threatening complications during treatment, hence the need to seek alternative sources of L-asparaginase. In this study, the novelty of upstream and downstream bioprocessing of L-asparaginase from a fungal endophyte, Colletotrichum gloeosporioides, and the cytotoxicity evaluation was demonstrated. Six variables (carbon source and concentration, nitrogen source and concentration, incubation period, temperature, pH and agitation rate) known to influence L-asparaginase production were studied using One-Factor-At-A-Time (OFAT) approach, with four significant variables further optimized using Response Surface Methodology (RSM). The crude extract produced using optimized condition was purified, characterized and examined for its anticancer effect. Purification of fungal L-asparaginase was performed via ultrafiltration and size exclusion chromatography, which are less common techniques. The protein profile and monomeric weight of L-asparaginase were determined using SDS-PAGE and Western blot. Cytotoxicity of purified L-asparaginase on leukemic Jurkat E6 and oral carcinoma cells were studied using MTS assay for 24 h and 48 h. OFAT results from optimization showed that glucose and L-asparagine concentrations, incubation period and temperature, were significant factors affecting L-asparaginase production by C. gloeosporioides. RSM analysis further evidence the significant interaction between glucose and L-asparagine concentrations in inducing L-asparaginase production. Purified L-asparaginase was profiled with specific activity of 255.02 IU/mg protein, purification fold of 6.12, and 34.63% of enzyme recovery. SDS and Western blot revealed that the purified L-asparaginase might be a tetramer with monomeric units of 25 kDa. Purified L-asparaginase was discovered to be more efficient against Jurkat leukemic cells than against H103 oral carcinoma cells, as lower IC50 value was observed for Jurkat cell lines (46 .36 ± 1.52 µg/mL for Jurkat and 125.56 ± 7.28 µg/mL for H103). In short, purified L-asparaginase derived from endophytic C. gloeosporioides showed high purity and significant anticancer effect toward cancer cells. This study therefore demonstrated the potential of fungal L-asparaginase as alternative chemotherapy drug in the future.