Valorization of olive mill wastewater towards the production of L-asparaginases

The use of several lignocellulosic and other organic wastes has been considered in literature for the production of L-asparaginases (L-ASNase); however, the use of olive mill wastewater (OMWW) has never been contemplated as culture media. OMWW is a widely available waste in the Mediterranean that needs to be treated due to its high pollutant load. In this work, OMWW is used to feed the strain Bacillus aryabhattai Ba03, which reduces the content in phenolic compounds and produces L-ASNase. A water dilution of OMWW to 25% (w/w) supplemented with 10 g/L of yeast extract at pH 8, incubated with the strain at 30 °C, was suitable for the production of 11.6 ± 0.3 U/mL extracellular L-ASNase after 2 days. In addition, the decrease of phenolic compounds together with the production of L-ASNase could be associated with the generation of aspartic acid and the expression of peroxidase activity. At the end of the bioprocess, salicylic acid was identified in the culture supernatant, assuming that chorismate metabolic pathway was followed by B. aryabhattai Ba03.