EFFECT OF NYSTATIN ON THE FORMATION OF EXTRACELLULAR PROTEASE BY ASPERGILLUS NIGER

Abstract

The effect of nystatin on the acid protease formation by Aspergillus niger as induced by sulfur deficiency was studied.
Nystatin at the concentration of 10μg/ml was found to inhibit the growth and the induced protease formation. The leakage of free amino acids from mycelia was also noted at this concentration. When nystatin was added to S-deficient cultures at different intervals in the induction period, a complete inhibition of protease formation was observed when added within the first 2.5hr. Later additions caused less effective inhibition.
After the protease induction in sulfur-deficient media, mycelia were either treated or not treated with nystatin and they were further cultured for protease formation on S-deficient media containing ¹⁴C-amino acid mixture. It was found that the nystatin-treated mycelium produced protease of higher specific radioactivity than the non-treated mycelium. This suggests that a fungal mycelium which has already established the protease-forming system can produce protease at the expense of exogenous nutrients, irrespective of the loss of the pool amino acid from the mycelium.