Barley straw as feedstock to produce bioproducts: evaluation of acid hydrolysis process

The demand for the development of biorefineries drives the researches for the utilization of waste or co-products from agro industry. In Brazil are produced around 350.000 tons per year of barley, resulting in large amount of barley straw. Residual non-food parts of barley straw may be a promising substrate for microbial fermentation to different bio-based products. It contains mainly cellulose (31-45%), hemicellulose (27-38%) and lignin (14-19%) fractions that may be hydrolysed to deliver solutions rich in sugars C6 and C5. C5 sugars, namely xylose is a substrate for the production of bioproducts, like ethanol and xylitol. Therefore, optimum conditions for acid hydrolysis of barley straw were investigated. The hydrolysis were carried out under different condition of temperature (120–140ºC), reaction time (20–40min), sulfuric acid concentration (0.5-1.0%) and dry weight/acid solution (1:8-1:12), according to a central composite design face-centered of 19 tests, including three replications at the center point. Quadratic polynomial model was adjusted to the date predict the behavior of response, namely extraction efficiency (E). The maximum value of extraction efficiency was found using 1:13.5 dry weight/acid solution, 2.6% of H₂SO₄ at 120ºC for 20min, which ensured E=84%, with high sugars release and low formation of toxic compounds. The main components (g L^-1) in the hemicellulosic hydrolysate were xylose, 20.92; glucose, 3.99; arabinose, 0.94; furfural, 0.06; hydroxymethilfurfural, 0.0096; acetic acid, 1.86 and phenols, 2.26. The hemicellulosic hydrolysate obtained revealed to have appropriate characteristics to be used in bioproducts production and the next stage will be to evaluate its fermentability. Acknowledgments: CAPES/CNPq