Supplementations of ornithine and KNO3 enhanced bacitracin production by Bacillus licheniformis LC-11

Abstract

During the fermentative process of Bacillus licheniformis LC-11, the dissolved oxygen (DO) and ornithine (Orn) content in the medium fell to zero, indicating that they were the potential limiting factors for cell growth and/or bacitracin biosynthesis. In addition, given that the nitrate-reducing system existing in B. licheniformis could favor cell anaerobiosis, the impacts of KNO3 and Orn supplementations were therefore evaluated for improving bacitracin production in both a shaking flask and a 10-L fermentor. Orn supplementation (0.04 g/L) at 16 h or KNO3 addition (0.5 g/L) in the production medium enhanced bacitracin production by 5.8 and 3.7 %, respectively. The combined effects of KNO3 and Orn supplementations were then conducted via a two-level central composite design, resulting in a predicted maximum bacitracin yield of 821.81 U/mL if KNO3 and Orn were supplemented at 514.39 mg/L and 45.35 mg/L, respectively. This predicated yield was then verified experimentally in a 10-L fermentor, achieving a 10.8 % increased bacitracin production (825 U/mL) over that of the control.