Improved production by fed-batch cultivation and some properties of Cu/Zn-superoxide dismutase from the fungal strain Humicola lutea 103

Cu/Zn-containing superoxide dismutase (Cu/Zn-SOD) from the fungal strain Humicola lutea 103 is a naturally glycosylated antioxidant enzyme which has been demonstrated to have a protective effect against myeloid Graffi tumor in hamsters and experimental influenza virus infection in mice. In this work, an improvement of enzyme production was achieved by using both an improved growing strategy and a more efficient purification protocol. The optimized fed-batch cultivation, with 7.5 mg/ml glucose fed daily after 24 h, resulted in prolonged growth and abundant mycelium production, as well as in improvement in enzyme production. A 2-fold increase in the total SOD activity and a significant increase in enzyme production were achieved (from 1.5- to 3.2-fold). Fed-batch technology contributed to a 24 h stabilization period of biosynthesis in which every stop of fermentation can be acceptable, thus making this fermentation a process of industrial interest. In addition, the improved purification procedure offers a reduction of purification steps and enhanced enzyme yield (1.6-fold).The molecular mass was proven to be 15,940 Da for the subunit and the conformational dynamics of the protein in solution was studied by electrospray ionization mass spectrometry (ESI-MS).