Screening and Media Optimization for Enhancing L-asparaginase Production, an Anticancer Agent, from Different Filamentous Fungi in Solid State Fermentation

Abstract

Aim: The aim of present study was to screen new potent fungal isolates and microorganisms possessing extracellular L-asparaginase production capacity. In addition, optimization of cultural and environmental conditions required for enzyme production will be carried out for the highest L-asparaginase producer in solid state fermentation (SSF) technique using agro-industrial residues. Study Design: Screening and physiological studies on the formation of L-asparaginase by Trichoderma viride F2 in order to obtain the optimum cultural and environmental conditions required for enzyme production. Place and Duration of Study: Department of Microbial Chemistry, Genetic Engineering and Biotechnology Division, National Research Centre (NRC), Cairo, Egypt, between July 2013 and June 2015. Methodology: Optimization of physical and nutritional parameters for enzyme production was investigated. Various locally available agro-industrial residues have been screened individually or as mixtures for L-asparaginase production. The combination of Rice husk (RH) with wheat bran (WB) (3:2) proved to be an efficient mixture for enzyme production as it gave the highest enzyme activity (71.87±3.19 U/g-ds) when compared to individual RH (66.71±2.76 U/g-ds) or WB (62.28±2.13 U/g-ds) substrates. Results: Maximal L-asparaginase production (113.43±5.11 U/g-ds) by T. viride F2 was obtained with moisture content of 75%, an inoculums size of 1 x 108 spores/ml and an initial medium pH of 5.0 when incubated at 28ºC for four days. Presence of Tween 20 enhanced enzyme production by 1.19 folds. Glucose (1.0%), Casein (1.5%) and MgCl2 (0.05%) were found to be the best carbon, organic nitrogen and ion sources, respectively. Supplementation of the medium with NaNO3 (0.15%) as an inorganic nitrogen source further increased L-asparaginase production. Under these optimized conditions, L-asparaginase production by T. viride F2 was maximum with a yield of 276.5±13.4 U/g-ds in SSF, which was more than 19-fold enhancement in enzyme activity as compared to that obtained in the basal medium (SmF) (14.23±0.87 U/ml). Conclusion: The results suggest that choosing a suitable substrate coupled with optimization of different parameters can improves enzyme production markedly. Moreover, the production of L-asparaginase from a process based on RH and WB as substrates in SSF is economically attractive due to abundant substrates availability in agriculture-based countries with cheaper cost.