Enhanced production of extracellular ribonuclease from Aspergillus niger by optimization of culture conditions using response surface methodology

Response surface methodology were used to study the cumulative effect of the culture conditions and to enhance the production of extracellular ribonuclease in shake flask fermentation by Aspergillus niger. These conditions considered include initial pH, inoculum size, total carbon, ratio of glucose to corn powder, NH4NO3 and K2SO4. The relative importance of these conditions on ribonuclease production was investigated by using the Plackett-Burman experimental design. Initial pH, ratio of glucose to corn powder and NH4NO3 were found to significantly influence the ribonuclease production. For obtaining the mutual interaction between the variables and optimizing these variables, a 23 factorial central composite design using response surface methodology was employed. Initial pH has a significant positive effect on the ribonuclease production. NH4NO3 has a significant negative effect. The mutual interactions have no significant effect. The ribonuclease production was increased by 23.2% compared to that under unoptimized conditions. The fermentation time was also shortened after optimization. (C) 2004 Elsevier B.V. All rights reserved.