Regulation of butanol biosynthesis in Clostridium acetobutylicum ATCC 824 under the influence of zinc supplementation and magnesium starvation.

Present study reports modulation in butanol biosynthesis in Clostridium acetobutylicum ATCC 824 under the influence of zinc supplementation or magnesium starvation either individually or in combination. An improvement in butanol titer from 11.83 g L-1 in control to 13.72 g L-1, 15.79 g L-1, and 19.18 g L-1 was achieved when organism was grown on magnesium starved, zinc supplemented and combined zinc supplemented-magnesium starved fermentation medium, respectively. The elevation in butanol biosynthesis was associated with raised glucose utilization, reduced ethanol production and early induction of solventogenesis. Change in these phenotypic traits of the organism may be attributed to multi-level modulation in central carbon metabolism e.g., upregulation of glycolytic pathway; upregulation in thiolase activity; key intermediate enzyme for biosynthesis of acids and solvent; upregulation in the activity of butyrylaldehyde dehydrogenase & butanol dehydrogenase, the enzymes responsible for butanol biosynthesis and downregulation in alcohol dehydrogenase, redirecting carbon flux from ethanol to butanol.

Nutrient modulation based process engineering strategy for improved butanol production from Clostridium acetobutylicum.

The present study demonstrates a process engineering strategy to achieve high butanol titer and productivity from wild type Clostridium acetobutylicum MTCC 11274. In the first step, two different media were optimized with the objectives of maximizing the biomass and butanol productivity, respectively. In the next step, attributes of these two media compositions were integrated to design a two-stage fed-batch process which resulted in maximal butanol productivity of 0.55 g L-1 h-1 with titer of 13.1 g L-1 . Further, two-stage fed-batch process along with combinatorial use of magnesium limitation and calcium supplementation resulted in the highest butanol titer and productivity of 16.5 g L-1 and 0.59 g L-1 h-1 , respectively. Finally, integration of the process with gas stripping and modulation of feeding duration resulted in a cumulative butanol titer of 54.3 g L-1 and productivity of 0.58 g L-1 h-1 . The strategy opens up possibility of developing a viable butanol bioprocess. © 2019 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2771, 2019.