Exploring the use of high solid loadings in enzymatic hydrolysis to improve biobutanol production from brewers' spent grains

Abstract

AbstractBrewers' spent grain (BSG) is a promising agroindustrial waste for the production of biobutanol. One critical point in the butanol production process is the optimization of the enzymatic hydrolysis step. In order to obtain the maximum efficiency, it is necessary to use high solids loadings in this process to obtain high concentrations of monosaccharides that allow high titres of butanol to be produced in the ABE fermentation process. The optimum enzyme and solids load maximizing the monosaccharide concentrations and minimizing the phenolic compounds concentrations in the enzymatic hydrolysates from pretreated BSG have been investigated. A dilute sulphuric acid pretreatment was carried out previously to the optimization of the enzymatic hydrolysis. Under optimal conditions (28.1% w/w solids load and 15.4 FPU/g DM), 47.0 g/L of glucose, 16.8 g/L of xylose, and 1.2 g/L of phenolic compounds were attained in the enzymatic hydrolysates. The enzymatic hydrolysates were subjected to an ABE fermentation process (with and without previous detoxification with activated carbon) to evaluate the production of butanol by C. beijerinckii. Maximum global yields of 31.0 g butanol/kg pretreated BSG and 46.4 g ABE/kg pretreated BSG were obtained. The detoxification process had little to no effect on the ABE fermentation process.