Citric acid production by Candida lipolytica Y 1095 in cell recycle and fed‐batch fermentors

The effect of dissolved oxygen on citric acid production and oxygen uptake by Candida lipolytica Y 1095 was evaluated in cell recycle and fed‐batch fermentation systems. The maximum observed volumetric productivity, which occurred at a dilution rate of 0.06 h −1 , a dissolved oxygen concentration of 80%, and a biomass concentration of 5% w/v, in the cell recycle system, was 1.32 g citric acid/L · h. At these same conditions, the citric acid yield was 0.65 g/g and the specific citric acid productivity was 24.9 mg citric acid/g cell · h. In the cell recycle system, citric acid yields ranged from 0.45 to 0.72 g/g. Both the volumetric and specific citric acid productivities were dependent on the dilution rate and the concentration of dissolved oxygen in the fermentor. Similar productivities (1.29 g citric acid/L · h) were obtained in the fed‐batch system operated at a cycle time of 36 h, a dissolved oxygen concentration of 80%, and 60 g total biomass. Citric acid yields in the fed‐batch fermentor were consistently lower than those obtained in the cell recycle system and ranged from 0.40 to 0.59 g/g. Although citric acid yields in the fed‐batch fermentor were lower than those obtained in the cell recycle system, higher citric:isocitric acid ratios were obtained in the fed‐batch fermentor. As in the cell recycle system, both the volumetric and specific citric acid productivities in the fed‐batch fermentor were dependent on the cycle time and dissolved oxygen concentration. © 1995 John Wiley & Sons, Inc.