Improvement of acid protease production by a mixed culture of Aspergillus niger and Aspergillus oryzae using solid-state fermentation technique

The synthesis of acid protease by Aspergillus oryzae AS3042 was enhanced significantly with the mixed culture of Aspergillus niger SL-09 using solid-state fermentation technique. The influence of carbon sources, nitrogen sources and the addition of phytic acid on acid protease production were investigated. The enzyme production varied depending on the nitrogen source. Apart from that, it was found that the enzyme activities formed in the mixed culture were enhanced dramatically by the addition of phytic acid to the medium. The response surface methodology (RSM) was used to optimize the medium composition for the production of acid protease and by this method the enzyme activity was enhanced near 5-fold higher than that obtained in the basal medium. Key words: Acid protease, Aspergillus niger, Aspergillus oryzae, solid-state culture, optimization, response surface methodology (RSM).