Optimization of L-Asparaginase production from Aspergillus caespitosus: solid-state and submerged fermentation using low-cost substrates and partial purification

This work aimed to optimize the production of L-asparaginase (L-ASNase) from Aspergillus caespitosus CCDCA 11593 using Pereskia aculeata (Ora-pro-nóbis) leaf fiber as a substrate for solid-state fermentation (SSF), along with powdered whey protein as a substrate in submerged fermentation (SmF) processes. A centered face design was applied to evaluate the effect of the different parameters. Additionally, L-ASNase was partially purified on an ion-exchange cryogel column. For SSF, the experimental condition, inoculum concentration 105 spores/mL, 120 h at 25 °C, 14% of substrate, and 1% of asparagine, corresponded to the highest enzymatic activity (2.75 U/mL) of L-ASNase. For SmF, the experimental condition of greater enzymatic activity (1.49 U/mL) was obtained in the medium containing 16% to 24% asparagine, 3.3% to 4.7% substrate, spore concentration of 7 × 106 to 107 spores/mL, temperature range of 29.8 to 34.8 °C, pH range of 5.7 to 6.3, and 87 to 105 h of fermentation. The L-ASNase obtained from SmF was subjected to adsorption tests, resulting in 4.4 U/mg of partially purified enzyme. This study suggested that whey protein and Ora-pro-nóbis leaf fiber could be a low-cost substrate for L-ASNase production. Additionally, using an ion-exchange cryogel column for enzyme purification holds promise for sustainable applications in the clinical and food industries.