Improved cultivation of the indigenous acidithibacillus thiooxidans BC1 by a fed-batch process

In this study, a simple fed-batch process was developed for high cell density culture of the indigenous Acidithiobacillus thiooxidans BCl for enhanced production of sulfuric acid. Since the inhibitory effect of the metabolic intermediate, sulfite, occurs in the acidic condition, pH control is important in the growth of this microorganism. In addition, elemental sulfur is the sole energy source for the indigenous A. thiooxidans BCl, a fed-batch process including the intermittent feeding of elemental sulfur was proved to avoid the effect of substrate limitation and inhibition, which was resulted from the sulfur accumulation in the air-liquid interface. The maximal cell density and sulfuric acid yield obtained in this study were 2.16 and 3.25 times, respectively, higher than those obtained from the conventional batch process. The optimal operation condition for the fed-batch process was set as: intermittent feeding of additional 2 g/L elemental sulfur at the same time when the pH value was adjusted from 2.0 to 4.0.