Flux balance analysis of nutritional modulation assisted changes in two-stage fed-batch fermentation by Clostridium acetobutylicum

Abstract

Flux balance analysis was performed to understand the mechanism governing metabolic versatility of Clostridium acetobutylicum under two different growth conditions: two-stage fed-batch fermentation (control) and two-stage fed-batch fermentation with magnesium limitation and calcium supplementation. Our key findings were: (i) increased ATP demand due to improved growth during magnesium-limited stage one of two-stage fed-batch fermentation was fulfilled by increased carbon flux towards acid synthesis pathways, which in turn aided early induction of solventogenesis; (ii) continued higher carbon flux towards growth concomitant to butanol pathways and lower non-growth associated maintenance energy were observed during calcium-supplemented stage two of two-stage fed-batch fermentation; (iii) pathways related to biomass and butanol synthesis were found to remain concomitantly active during acidogenesis and solventogenesis under combinatorial usage of magnesium limitation-calcium supplementation in two-stage fed-batch fermentation.