Production and characterization of L-asparaginase by Aspergillus niger: A sustainable use of pitaya (Hylocereus spp.) by-products

The present study focused on the optimization of the L-asparaginase production by solid-state fermentation from Aspergillus niger INCQS 40018 (ATCC 1004) using pitaya by-product and the determination of its biochemical characterization. The L-asparaginase production was carried out at 25 °C using L-asparagine as an inducer to determine the best production time. The experiments of optimization process were performed in a 4² fold complete factorial design to evaluate the effect of the variables moisture and inducer concentration. For the enzyme characterization, the thermostability was studied with varying temperature of 20–70 °C, and the pH ranging from 3.0 to 11.0. The effect of NaCl, CaCl₂, KCl, CuSO₄ and EDTA at concentrations of 1 mM and 5 mM was also studied. The results showed that 36 h was the best time for L-asparaginase production and the variables studied were significant in the optimization process that presented an increase of 58.96 %. The enzyme produced obtained optimal activity at 40 °C and pH 5.0, and remained stable in the temperature range of 20 °C to 40 °C and pH of 4.0–5.0. Regarding the effect of the compounds studied, NaCl, CaCl₂, and EDTA had an activating action on the enzyme, while KCl and CuSO₄ showed an inhibitory action at the concentration of 5 mM. At a concentration of 1 mM, all the compounds inhibited the L-asparaginase. Overall, the results indicate the potential for the sustainable use of pitaya by-product for the L-asparaginase production with promising biotechnological capacity.