Development of a cost-effective medium for submerged production of fungal aryl alcohol oxidase using a genetically modified Aspergillus nidulans strain.

Aryl alcohol oxidase (AAO), an extracellular H2O2-providing enzyme, plays a central role in lignin depolymerization. Cost-effective production of AAO has not been achieved, due to the low yield of enzyme-producing microorganisms and the high cost of fermentation media. This study aims to develop a cost-effective medium for high-yield production of AAO in submerged culture using a recombinant Aspergillus nidulans strain. Results demonstrate that corn steep liquor (CSL) was a rich but inexpensive nitrogen source for AAO production, and CSL can provide enough trace metals and vitamins (i.e. pyridoxine) for A. nidulans. A 2-level Plackett-Burman design was utilized to determine the main affecting factors in AAO production. The medium was further optimized by a 3-level Box-Behnken design to obtain the optimum medium component concentrations (61.0 g/L maltose, 26.4 g/L CSL, and 13.8 g/L NaNO3). The greatest AAO activity achieved was 1021 U/L with a protein concentration of 0.75 g/L.