Mechanistic investigations in biobutanol synthesis via ultrasound-assisted ABE fermentation using mixed feedstock of invasive weeds.

Graphical abstract Highlights • Ultrasonic ABE fermentation using C. acetobutylicum and mixed invasive weeds. • Net ABE solvent yield with sonication = 0.288 g/g raw biomass in 92 h fermentation. • Analysis of substrate and metabolites profiles using biokinetic model. • Sonication boosts kinetics of metabolism with reduced saturation constants. • Flow cytometry analysis revealed high cell viability during exposure to sonication. Abstract This study reports an ultrasound-assisted Acetone-Butanol-Ethanol (ABE) fermentation process using Clostridium acetobutylicum MTCC 11,274 and mixed feedstock consisting of eight highly invasive weeds. Composite (pentose + hexose) hydrolyzate was fermented with sonication at 35 kHz and 10% duty cycle (test) and mechanical agitation at 150 rpm (control). Net solvent yield with sonication was 0.288 g/g raw biomass in 92 h against yield of 0.168 g/g raw biomass in 120 h with mechanical agitation. Butanol yield in test and control fermentation was 0.233 and 0.149 g/g total fermentable sugar, respectively. Substrate and metabolites profiles in test and control fermentation were analyzed using biokinetic model. Sonication enhanced kinetics of metabolic reactions with rise in substrate affinity of enzymes (reduced saturation constants) and greater resistance to substrate inhibition. Flow cytometry analysis of cells exposed to sonication revealed high cell viability with no adverse effect on physiology. [ABSTRACT FROM AUTHOR]