Submerged Citric Acid Fermentation of Ferrocyanide-Treated Beet Molasses: Morphology of Pellets of Aspergillus Niger

A study of the internal structure of Aspergillus niger pellets, grown during submerged citric acid fermentation of ferrocyanide-treated beet molasses, was made using botanical microtechniques. Under optimum fermentation conditions, each pellet developed as a round mass of mycelium of uniform consistency during the first 24 hours of the fermentation (mash sparged with air); subsequently (mash sparged with oxygen), a dense crust of growth formed at the periphery of the pellet and autolysis of cells at the center began. At the end of fermentation (140 hours), the pellet consisted of a shell of mycelium occupying less than 50% of the pellet volume. Changes in fermentation conditions were reflected in the density of peripheral growth and in the rate and extent of autolysis.