Production of citric acid from glycerol

In this study, a glycerol which is a common biodiesel byproduct was used to produce citric acid by fermentation using strains of Aspergillus niger. The culture medium contained glycerol as the carbon source, yeast extract as the nitrogen source and KHzP04 and Na2HP04 as the phosphate source as well as other essential nutrients for the fungae. The parameters studied were incubation temperature, nitrogen content, phosphate content and addition of additive. Eight experiments were done to determine the most optimum conditions. Titration of the product citric acid with 0.1 M NaOH was done to obtain the concentration and yield of citric acid of all experiments. The result obtained proved that citric acid production was most optimum when the incubation temperature was at 30°C, nitrogen contents at 0.01 to 0.04 g per 100 m1 and the phosphate content at 0.7 g per 100ml. Also when ethanol at 3.0 % v/w was used as an additive in the medium the yield of citric acid increased. Experiment eight with the additive and with the optimum conditions mentioned above produced the highest yield of citric acid at 1.00 %. Meanwhile the lowest yield of 0.25 % was obtained for experiment 5 when the nitrogen amount was altered to 0.005 g. Experiment one was taken as the control experiment with the optimum conditions as above but without the addition of the additive. The characterization of citric acid was done using a reverse phase HPLC. The most optimum yield was used for characterization purpose and was compared to a standard solution of citric acid of 0.1 M. The standard solution of citric acid produced a peak with a retention time of 1.427 minute and area of 92.2482 % while the experimental citric acid had a retention time of 1.288 minute and area of 95.0131 % ..