Production of ethanol from the hemicellulosic fraction of sunflower meal biomass

Abstract

Researches on second-generation ethanol, produced from agroindustrial wastes, have demanded special attention as a possible solution to energy sustainability. Such production is based on lignocellulosic fiber conversion, which generates fermentable sugars that are biotransformed into ethanol. This work aimed at evaluating ethanol production by the yeast Pichia stipitis ATCC 58376 in the hemicellulosic hydrolysate of sunflower meal biomass, a subproduct generated by sunflower oil manufactures. Sunflower meal was submitted to dilute acid hydrolysis with 6 % (w/v) H2SO4 in autoclave, at 121 °C, for 20 min and resulted in a hemicellulosic hydrolysate with high concentration of sugars (24.98 g/L xylose, 26.55 g/L glucose, and 6.51 g/L arabinose) and low amounts of toxic compounds (3.04 g/L total phenols, 0.58 g/L acetic acid, 0.40 g/L furfural, and 0.09 g/L hydroxymethylfurfural). The fermentations of the detoxified hydrolysate were conducted in Erlenmeyer flasks at 30 °C, initial pH 5.5, under different agitation speeds (100, 150, and 200 rpm). The best ethanol production (8.8 g/L ethanol, yield of 0.23 g/g, and productivity of 0.12 g/L h) was attained at 200 rpm. The results demonstrate that sunflower meal is a promising biomass for ethanol production from its hemicellulosic fraction. In addition, the hemicellulosic hydrolysate has the advantage of not requiring a sugar concentration step, which contributes to the economic viability of the process.