AbstractIt is of general interest to produce fermentable carbohydrates from plant biomass. However, obtaining monosaccharides requires some effort, due to the intricate structure of the cell wall lignocellulosic complex. The aim of this study was to apply a simple two-stage hydrolysis process, using only concentrated hydrochloric acid, to generate fermentable carbohydrates from L. rotundiflorus biomass. First and second stage acid concentrations were 32% and 42.6%. Total monosaccharide yields with respect to dry matter after the first stage, second stage, and the overall process, were 27.5%, 21.0% and 48.4%, respectively. Xylose was the main first stage carbohydrate in the hydrolysate, followed by glucose, arabinose, and galactose. After the second stage only glucose and a small amount of xylose were detected. The polysaccharide hydrolysis was eased by overall low lignin content. Some advantages of this method were the use of a single hydrolyzing agent and that most of the polysaccharides were hydrolyzed in reasonably high yields. The acceptable yield, relative simplicity, the use of most of the biomass along with the wide availability, low cost of the chemicals, and the ample supply of lupines, would facilitate the scaling of these laboratory studies to pilot and industrial levels.