Biorefinery of barley straw using pressurized fluids: Biocompounds and biopolymers production

Abstract

In this study, barley straw was treated by subcritical water (sCW) and pressurized aqueous ethanol (PAE) (20–100% v/v ethanol) at 180–220 °C, 50–200 bar, 5 mL/min, for 40 min. The optimum condition to obtain monosaccharides was using sCW at 200 °C, 50 bar for 40 min with the highest contents of xylose (48.63 ± 2.95 mg/g barley straw) followed by glucose (17.85 ± 1.01 mg/g barley straw) and arabinose (7.20 ± 1.15 mg/g barley straw). The highest content of total phenolics in the hydrolysates (75.38 ± 1.43 mg GAE/g straw) and lignin removed in the residue (7.5% lignin left) were achieved by PAE (60%) at 220 °C, 50 bar, for 40 min, resulting in 88.43% of cellulose in the residue. In addition, the use of PAE treatments at higher ethanol concentrations significantly reduced the formation of inhibitors such as 5-HMF and furfural. Furthermore, PAE hydrolysates had antioxidant activity values in the range of 23.87–82.62 mM FeSO4/g straw.