Process and Strain Development for Reduction of Broth Viscosity with Improved Yield in Coenzyme Q10 Fermentation by Agrobacterium tumefaciens ATCC 4452

Abstract

Viscous nature of the fermentation broth has phenomenal influence on process conditions and parameters in a fermentor. Though broth rheology has attracted significant influence in process research, still there is a challenge to modify fluid dynamics of fermentation broth. During the production of coenzymeQ10 (CoQ10) by Agrobacterium tumefaciens ATCC 4452, the culture broth becomes highly viscous due to excessive synthesis of exopolysaccharides. This hinders the CoQ10 yield and complicates the downstream process. The present study describes how this problem was tackled by media modification and mutation. Induced mutants were generated using UV and EMS as mutagenic agents followed by rational selection based on antibiotic resistance. On screening of these mutants in sucrose based PM-2 medium, UV induced, vancomycin resistant mutant M-6, showed significant reduction (6.29 fold) in viscosity development in the broth. Mutant M-6(S), a natural variant of mutant M-6, resistant to high substrate concentration was further selected for the CoQ10 production. Cane molasses as carbon source was found to be best suitable for CoQ10 fermentation using mutant M-6(S). Replacing sucrose with cheaper cane molasses significantly reduced the broth viscosity with improved specific CoQ10 content, thereby generating cost effective fermentation process. The newly developed mutant strain produced 48.89 mg/L of CoQ10 with specific CoQ10 content of 1.87 mg/g of DCW at 25°C, 500 rpm agitation and 0.2 vvm aeration using continuous fed batch fermentation and newly formulated cane molasses medium.