Activation of dissimilatory nitrite reduction to ammonium for improved butanol biosynthesis

Extensive studies have focused on improving lignocellulosic butanol production through the optimization of growth media and feedstocks. However, the stimulatory potential arising from the inherent physiological traits of the microbial strains used in fermentation has been significantly overlooked. In this study, by supplementing ammonium, nitrate, and nitrite, we demonstrated that short-cut dissimilatory nitrate reduction to ammonium (short-cut DNRA), defined as the dissimilatory reduction of nitrite to ammonium, was associated with enhanced butanol production by Clostridium sp.strain MF28. Results indicated that nitrite was completely reduced to ammonium by strain MF28 within 20 h, and the ammonium generated was subsequently assimilated by strain MF28 during fermentation. Butanol concentrations reached 17.9 g/L and 18.7 g/L (increased by 81.3% and 88.7%) after fermenting 80 g/L glucose upon the addition of nitrite or ammonium, both at an optimal concentration of 10 mM. This enhancement was accompanied by the elevated strain abundance and the upregulated transcription of genes associated with ammonia assimilation and the butanol biosynthesis. These mechanistic insights highlight the significance of strain-specific physiological traits, suggesting a broader application potential of strain MF28.