Abstract
With all the media investigated citric acid yield increased with the age of culture of Aspergillus niger 599. The extent of this yield was related to the composition of the medium but not to the mycelial growth or spore formation. With most media, this was also the case of the extracellular polygalacturonase activity. No pectin-methylesterase was formed either in the fermentation broths or the mycelia. The effect of addition of pectin, methanol, or pectin+methanol to the culture media on the production of the metabolites was investigated. The results indicated a consistent relationship between citric acid production and both extracellular and intracellular polygalacturonase activities in molasses media. The ratio of extracellular to intracellular polygalacturonase activity varied from one medium to another, and with the age of culture of the same medium.
