SELECTION OF A STRAIN OF ASPERGILLUS FOR THE PRODUCTION OF CITRIC-ACID FROM PINEAPPLE WASTE IN SOLID-STATE FERMENTATION

Aspergillus foetidus ACR I 3996 (=FRR 3558) and three strains of Asper gillus niger ACM 4992 (=ATCC 9142), ACM 4993 (=ATCC 10577), ACM 4994 ( =ATCC 12846) were compared for the production of citric acid from pine apple peel in solid-state fermentation. A. niger ACM 4992 produced the highest amount of citric acid, with a yield of 19.4 g of citric acid per 100 g of dry fermented pineapple waste under optimum conditions, r epresenting a yield of 0.74 g citric acid/g sugar consumed. Optimal co nditions were 65% (w/w) initial moisture content, 3% (v/w) methanol, 3 0 degrees C, an unadjusted initial pH of 3.4, a particle size of 2 mm and 5 ppm Fe2+. Citric acid production was best in flasks, with lower yields being obtained in tray and rotating drum bioreactors.