Hydrolysate detoxified from steam exploded corn cob and its fermentation producing butanol fuels

Abstract: The development and utilization of biomass have been paid great attention by many countries with the depletion of fossil energy sources. Due to the recalcitrant and complex structure of lignocellulosic biomass, various pretreatment methods are adopted to help biomass carbohydrate's hydrolysis. Pretreatment can increase the biomass digestibility for efficient fermentable sugar production, but many fermentation inhibitors are also produced during this process, such as furan derivatives (furfural and 5-hydroxymethylfurfural), mini-molecule organic acid (acetic acid and formic acid), and lignin degradation products (coumaric acid, vanillin and other phenolics). Therefore, the detoxification process which removes fermentation inhibitors from hydrolysates is essential for the production of biomass energy; at the same time, for different fermentations have different adaptability of initial sugar concentration in fermentation liquor, the studies about the optimal initial sugar fermentation concentration are also meaningful. In order to study the best technology of butanol fuel production from steam exploded corn cob, 4 detoxification methods, which were over liming, D301 resin, over liming combined with D301 resin, and over liming combined with NKAII macro porous resin, were used to detoxify the hydrolysate of steam exploded corn cob, and their effects on butanol production were also determined in this research. The results showed that the D301 resin detoxification was the most efficient way to detoxify the hydrolysate of steam exploded corn cob. The removal ratio of vanillin could reach 100%; the removal ratio of formic acid, acetic acid, total phenol, furfural and 5-hydroxymethylfurfural reached 60%, 46.04%, 56.31%, 82.95% and 87.52%, respectively. At the same time, total sugar lost ratio was only 4.38%. Finally, butanol and ABE (actone, butanol, ethanol) production were 5.2 and 7.5 g/L by fermentation with C. acetobutylicum CICC 8016, and the utilization rate of glucose and total sugar reached 100% and 73.67%, respectively. When the initial sugar concentration was 50 g/L in the detoxified corn cob hydrolysate, the maximum concentrations of butanol and total solvent were 9.7 and 14.6 g/L respectively after 96 h fermentation. The over liming and over liming combined with NKAII macro porous resin had poor inhibitor removal ratio and lower butanol production (no more than 1.0 g/L butanol was produced). Although over liming combined with D301 resin had higher inhibitor removal ratio, only 2.4 g/L butanol and 3.3 g/L ABE were produced because of high sugar lost ratio (about 41.59% glucose and 15.88% xylose were lost during the detoxification). In conclusion, the D301 resin detoxification is an idea process for butanol production from lignocellulose hydrolysate because of its high microbial inhibitor removal ratio and low sugar loss. This research provides a reliable detoxification method for butanol fermentation with the hydrolysate of steam exploded corn cob.