Different response between woody core and bark of goat willow (Salix caprea L.) to concentrated phosphoric acid pretreatment followed by enzymatic saccharification

Different response between woody core and bark of goat willow biomass to concentrated phosphoric acid pretreatment prior to enzymatic saccharification was investigated as changes of chemical compositions, carbohydrate compositions, and crystallinity of cellulose before and after pretreatment. Goat willow has different chemical composition between bark and woody core, higher polysaccharides content in woody core as 74.6% compared with 61.0% in bark. In bark, hydrophobic and hydrophilic extractives contents was 20.4% compared with 8.1% in woody core. Parts of extractives and carbohydrates were removed by concentrated phosphoric acid pretreatment, and this trend was more obvious in bark than woody core. In bark, 60% of xylan and 30% of cellulose was removed by acid pretreatment but only 40% of xylan and 8.3% of cellulose in woody core. Removal of polysaccharides in cell wall and destruction of crystal structure (cellulose crystallinity reduction) in cellulose caused the more enzymatic saccharification by commercial cellulases cocktails. Bark showed three times higher cellulose to glucose conversion by cellulases but woody core was two times higher than those of untreated. •Phosphoric acid pretreatment decreased the crystallinity of cellulose and removed xylan.•More xylan removal and decrystallization of cellulose occurred in bark than woody part.•Bark was more hydrolyzed than woody part by commercial cellulases.•Bark in Goat willow was good raw material for bio-alcohol production.