AbstractA pretreatment in tandem composed of sunlight or sun-like UV-irradiation, freezing-thawing, soda swelling, and boiling (never drying between treatments), was applied to a slurry of ground-up Lupinus rotundiflorus, followed by enzymatic hydrolysis. The effects were studied through an experimental design in which the factors were employed cumulatively to statistically evaluate the effect of each factor on enzymatic saccharification. Results showed that swelling and physical disarrangement of the lignocellulosic complex probably occurred with little or no delignification and soda consumption. The disarrangement of the cell wall and tissue structures generated by the combined effects of UV-light, freezing-thawing, soda swelling, and boiling contributed to a yield of up to 67.0% of fermentable sugars with respect to hydrolyzed material (82.8% of theoretical fermentable sugars). This yield was comparable to that obtained in control samples using Whatman No.1 paper, which produces a very high yield of fermentable sugars after hydrolysis. Finally, the acceptable overall results showed that improved saccharification of lignocellulosic materials by means of natural agents is feasible.