Acid-catalyzed steam explosion for high enzymatic saccharification and low inhibitor release from lignocellulosic cardoon stalks

uses. In this work, cardoon lignocellulosic stalks underwent to acid-catalyzed steam explosion. A design of experiments approach was employed to assess the effect of the process variables (acid concentration, temperature and reaction time) on xylan recovery after direct hydrolysis and cellulose digestibility in the enzymatic hydrolysis step. According to the statistical model generated, the optimal conditions to maximize overall monosaccharides yield were 166 ◦C, 1.45% (w/w) and 10 min. A monosaccharides production and inhibitors formation of 36.76 g/100 g raw material (close to 70% of the maximal theoretical yield) and 1.80 g/100 g raw material, respectively, were achieved. The scale-up of the hydrolysis step showed superior performance of the washed solid fraction than to the whole slurry, resulting in cellulose conversion to glucose by 76% vs 58%. By employing the life cycle assessment approach, it was possible to determine the environmental impact in terms of the global warming potential (3.18 kgCO2eq/kg of fermentable carbohydrates) and cumulative energy demand (43.34 MJ/kg of fermentable carbohydrates). The low-inhibitor and high-sugar hydrolysate can be fermented to biochemicals and biofuels without any detoxification process.