Citric Acid Fermentation by Immobilized Aspergillus niger in Cellulose Carrier
摘要
Various types of carriers were screened to immobilize\nwith Aspergillus niger for citric acid production. The\nscreening test showed that cellulose sponge was an\nexcellent immobilization carrier for citric acid\nfermentation wherein the yield of 45 g/1 was obtained\nafter 7 days of cultivation, while the yield with\nurethane foam as a carrier was 5 g/l. Using the cellulose\nsponge carrier which was earlier tested, the method of\nimmobilization in batch culture was investigated under\nvarying medium composition, medium concentration and\ncarrier packing rate. The highest productivity achieved\nwas 9.5 g/l-day at 55% packing rate when the basal medium\nconcentration was increased two times. However, increasing\nthe basal medium concentration three times, the maximum\nproductivity was 7 g/l-day at 40% packing rate.\nFurthermore, at basal concentration and at 30% packing\nrate, the maximum production of 95 g/l was reached when\nthe biomass density was 4 g/l. Results showed that\nproduction rates were also inhibited by other limiting\nfactors such as oxygen supply or nutrient distribution.\nIntroduction