Optimization of ABE fermentation to biobutanol production using bagasse and lignocellulosic hydrolyzate of sugarcane bagasse

Abstract

In the context of the production of second generation ethanol from sugarcane bagasse integrated into existing plants, an important fraction of sugars from the hemicellulose of this lignocellulosic material cannot be utilized by the yeast traditionally used in 1G plants. Among the various possibilities of using the pentose sugars (C5), n-butanol production has attracted commercial interest from different companies due to its use both as a chemical and as a biofuel. However, biobutanol production process via ABE fermentation is more complex than ethanol production and the economic viability of this process faces challenges such as high product inhibition and low yield. Direct effects of product inhibition are the low productivity and the energy inefficiency of the process as a result of the recovery of dilute product stream (~ 12 g butanol / L). Furthermore, in a process of the second generation, the ABE fermentation is also sensitive to inhibitors generated in the pretreatment of biomass. Given those challenges, this scientific initiation project proposes ways to enable the n-butanol production from pentose sugars in sugarcane bagasse. To this end, the use of molasses will be studied not only as a diluting agent of inhibitors generated in the pretreatment but also as a way to increase the concentration of sugars in the liquor pentoses. Optimization studies will determine the best composition of culture medium for the evaluated conditions. In order to facilitate the complete conversion of the sugars (molasses + C5) and enabling productivity gains, the process will also be studied using the vacuum fermentation technology that allows the in situ recovery of the product.