Reassessment of the role of CaCO 3 in n-butanol production from pretreated lignocellulosic biomass by Clostridium acetobutylicum

In this study, the role of CaCO 3 in n-butanol production was further investigated using corn straw hydrolysate (CSH) media by Clostridium acetobutylicum CICC 8016. CaCO 3 addition stimulated sugars utilization and butanol production. Further study showed that calcium salts addition to CSH media led to the increase in Ca 2+ concentration both intracellularly and extracellularly. Interestingly, without calcium salts addition, intracellular Ca 2+ concentration in the synthetic P2 medium was much higher than that in the CSH medium despite the lower extracellular Ca 2+ concentrations in the P2 medium. These results indicated that without additional calcium salts, Ca 2+ uptake by C. acetobutylicum CICC 8016 in the CSH medium may be inhibited by non-sugar biomass degradation compounds, such as furans, phenolics and organic acids. Comparative proteomics analysis results showed that most enzymes involved in glycolysis, redox balance and amino acids metabolism were up-regulated with CaCO 3 addition. This study provides further insights into the role of CaCO 3 in n-butanol production using real biomass hydrolysate.