Enhancing the enzymatic digestibility of bamboo residues by biphasic phenoxyethanol-acid pretreatment

[Display omitted] •91.6% of lignin in BR could be removed by acid/phenoxyethanol pretreatment.•Enzymatic yield of 91.3% was achieved for BR pretreated by phenoxyethanol.•Enzymatic yield linearly correlated (R2 > 0.7) to physicochemical property of BR.•Recycle preteatment liquor and using low enzyme still showed good enzymatic yield. The high content of lignin in bamboo is considered as the major obstacle for its biorefining. In this work, a green, lignin-selective, and recyclable solvent of phenoxyethanol was coupled with acid solution to deconstruct recalcitrant structure of bamboo residues (BR) to boost its enzymatic digestibility. Results showed phenoxyethanol has excellent lignin-removal ability from 29.4% to 91.6% when phenoxyethanol:acid ratios increased from 0:1 to 4:1 at 120 °C. 82.5%–87.8% of cellulose was preserved in pretreated BR. The enzymatic digestibility of BR significantly improved from 20.0% to 91.3% when it was pretreated under optimized conditions. With lower enzyme dosages (10 FPU/g) and 5 recycled using of pretreatment liquor, pretreated BR still showed a good enzymatic digestibility of 67.4%–93.7% and 67.1–76.8%, respectively. Examination of physicochemical changes revealed that improvements to accessibility, reduction of crystallite size, decrease of surface lignin and hydrophobicity for pretreated BR showed positive correlations (R2 > 0.7) with their enzymatic digestibility.