Enhanced aerobic conversion of starch to butanol by a symbiotic system of Clostridium acetobutylicum and Nesterenkonia

Abstract

The microbial pathway of butanol biosynthesis is a unique route for the production of a biomass-derived advanced biofuel with high potential to be utilized in place of the fossil fuels. In the present study, Nesterenkonia sp. strain F was applied as a beneficial partner for Clostridium acetobutylicum in “starch-to-butanol process”. The capability of Nesterenkonia sp. strain F in secreting organic solvent-tolerant amylase was utilized for upgrading the yield of solvent, i.e., acetone, butanol, and ethanol (ABE), production under aerobic conditions. Monitoring the amylolytic activity and glucose concentration throughout the micro-aerobic co-culture revealed higher amylase activity and glucose concentration in comparison with the monoculture. The co-culture led to 63% higher amylase activity through the microaerobic cultivation on starch. After optimizing the conditions with response surface methodology (RSM), 10.6 g/L butanol was produced from untreated potato starch (UPS) with a high yield of 0.23 g ABE/g starch, leading to 30% improvement in ABE production. To assess its performance at larger scale, the fermentation was conducted in a 5 L fermenter continually aerated with a rate of 0.05 vvm and 150 rpm. This led to production of 9.7 g/L butanol, 5.0 g/L acetone, and 0.3 g/L ethanol with a yield and productivity of 0.20 g/g and 0.21 g/L.h, respectively. Furthermore, ABE production from tannin-containing sorghum grain was improved by about 3-fold. © 2020 Elsevier B.V.