King Grass: A promising material for the production of second-generation butanol

Butanol is an alcohol that can be used as fuel and as intermediate in chemical synthesis. Due to its characteristics, butanol has a very high compatibility with gasoline. Concerns about non-renewable resources and environmental problems associated with petroleum have revived the interest for the biological pathway to produce butanol. Furthermore, the use of lignocellulosic biomass as feedstock has turned very attractive due its high availability. We found that the most suitable grass for butanol production in Colombia, based on availability, plant conditions, theoretical yield to solvents, crop timing and composition was King Grass. Samples of this species were characterized to determine their composition. Then, the material was pretreated by alkaline delignification and hydrolyzed with a commercial cellulase preparation, obtaining a maximum sugar content of 78 g/L. The hydrolysate was fermented with the bacteria Clostridium acetobutylicum ATCC 824 in simultaneous and separated hydrolysis and fermentation configurations. Separated hydrolysis and fermentation performed better than the simultaneous configuration. Best results were found when the fermentation was carried out without pH control, i.e.,18 g/L solvents and 10.4 g/L of butanol, which corresponds to 145 L of butanol per ton of pretreated biomass and to a maximum butanol yield of 4500 L per hectare per year.