Submerged citric acid fermentation of beet molasses in tank‐type fermenters

Ferrocyanide‐treated beet molasses was fermented in fully baffled mechanically agitated, 2.5‐liter, tank‐type fermenters using pellets of Aspergillus niger grown in shake flasks as an inoculum. The object of the study was to adapt the fermentation method previously developed in an unstirred tower‐type fermenter to a conventional tank‐type fermenter. Under selected conditions of stirring (agitator speed 400–700 rpm) and sparging (medium porosity sintered disk), high yields of citric acid (8.6% citric acid, 70% conversion of available sugar) were obtained in 140 hr. of fermentation. There was little relation between citric acid yield and aeration conditions in the fermenter as judged by mash viscosity measurements and sulfite oxidation studies.