Optimization of citric acid production from Candida lipolytica Y-1095 using n-paraffin

Currently, the majority of worldwide microbial production of citric acid ut ilizes Aspergillus niger in a carbohydrate based submerged fermentation. Du e to their high carbon content, hydrocarbons also have the potential of pro ducing high concentrations of citric acid. Initial lab experiments conducte d using 1875 ml batch fermentations with n-paraffin found that Candida lipo lytica NRRL-Y-1095 assimilated the feedstock and had a citric acid producti vity of 47 mg l-(1) h-(1). To determine the optimum level of initial biomas s concentration, n-paraffin concentration, iron concentration and temperatu re for the production of citric acid, a central composite design was develo ped using 200 ml batch fermentations. The design involved conducting 31 bat ch fermentations under various combinations of high and low values of these four parameters. From this investigation empirical models were developed d escribing the interactions between the experimental parameters and citric a cid production. It was found that the maximum concentration of citric acid produced was 9.8 g l-(1) and the optimum levels of each parameter for citri c acid production were, 10-12% volume for initial biomass concentration, 10 -15% volume for n-paraffin concentration, 10 mg l-(1) for ferric nitrate co ncentration, and 26-30 degreesC for temperature. (C) 2001 Elsevier Science B.V. All rights reserved.