Economic benefit from the optimization of citric acid production from rice straw through Plackett-Burman design and central composite design

An economic study was carried out to show the benefits of optimization during the production of citric acid from rice straw as a substrate by solid-state fermentation (SSF) using Aspergillus niger. The optimization procedure for the media components (NH4NO3, KH2PO4, MgSO4 , CuSO4 , ZnSO4, FeSO4 , and MnSO4) was carried out using Plackett-Burman design (PBD) for the screening and central composite design (CCD) for the optimization. The results obtained from PBD indicated that NH4NO3, KH2PO4 , and MgSO4 were the most significant components that affected the citric acid production. The maximum yield obtained by CCD was 50.23 g citric acid/kg rice straw. The rate of citric acid production by SSF after the optimization indicated a profit of about 65% for SSF without any nutrient addition and of about 27% for SSF without optimization.