PELLET GROWTH AND CITRIC-ACID YIELD OF ASPERGILLUS-NIGER-110

Inoculation methods and aeration conditions in the production of pellet cultures of Aspergillus niger 110 with acceptable citric acid yields were studied. Inoculating the fermentor with a preculture of pellets, instead of directly with spores, and carrying out fermentation at 1000 rev min** minus **1 from seeding resulted in fungus growth in the form of compact, smooth pellets of uniform size and excretion of 48. 0 g l** minus **1 of citric acid. In contrast, cultivation of this same type of inoculum at 450 rev min** minus **1 for the first 48 h, followed by 1000 rev min** minus **1 for the remainder of the fermentation period, gave rise to different types of pellets of varying size that yielded only 30. 3 g l** minus ** 1 of citric acid. Under these latter aeration conditions, increasing the air flow from 0. 9 to 1. 3 vvm raised the citric acid yield to 48. 7 g l** minus **1 while leaving fungus morphology unaffected.