Using response surface methodology to improve the L-asparaginase production by Aspergillus niger under solid-state fermentation

Microbial L-asparaginase have been used as a therapeutic agent in the treatment of acute lymphoblastic leukemia and Hodgkin's disease. In addition to clinical use, L-asparaginases have been used in foods to reduce the formation of acrylamide. L- asparaginase production is carried out mainly by submerged fermentation (SmF). However, solid-state fermentation (SSF) offers potential benefits compared with submerged fermentation, such as the use of low-cost agro-industrial residues as the substrate, which is very attractive for bioprocessing. The main objective of this study was to evaluate the use of agro-industrial wastes, including wheat bran, soybean meal, rice meal, chicken feather meal, chicken viscera meal and passion fruit peel flour, for L-asparaginase production by Aspergillus niger LBA 02 under solid-state fermentation. Among the substrates, the highest L-asparaginase activity was obtained using passion fruit peel flour (2380.11 U/gds) after 48 h of fermentation at 30 °C. The effects of temperature, initial moisture content (%) and inoculum concentration (spores/g) on the L-asparaginase production were evaluated using passion fruit peel meal as a substrate using Central Composite Rotatable Design (CCRD) with 17 runs. An increase in L-asparaginase activity (3746.78 U/gds) was obtained using the optimized conditions of passion fruit peel flour with an initial moisture content of 60% and inoculum concentration of 2.1 106 spores/g after 24 h of fermentation at 25 °C. It was observed that the process optimization resulted in a 57% increase in enzyme production compared with the initial values obtained in the “one-factor-at-a-time” method.