The influence of nitrogen sources on the alpha-amylase productivity of Aspergillus oryzae in continuous cultures

The influence of the nitrogen source on the cc-amylase productivity of Aspe rgillus oryzae was quantified in continuous cultivations. Both inorganic an d complex nitrogen sources were investigated and glucose was used as the ca rbon and energy sources. For production of alpha-amylase, nitrate was shown to be inferior to ammonia as a nitrogen source. A mixture of ammonia and c omplex nitrogen sources, such as yeast extract or casein hydrolysate, was b etter than with ammonia as the sole nitrogen source. Even a low concentrati on of casein hydrolysate (0.05 g l(-1)) resulted in a 35% increase in the c c-amylase productivity. The higher alpha-amylase productivity during growth on casein hydrolysate was not caused by increased transcription of the alp ha-amylase genes but was caused by a faster secretion of alpha-amylase or b y a lower binding of alpha-amylase to the biomass.