338 / 2018-07-31 10:17:45

Comparative investigations of various H2O2-involved pretreatments on lignocellulosic biomass for enzymatic hydrolysis

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Hydrogen peroxide (H2O2) is often used for lignocellulose pretreatment due to its high efficacy, low-cost and limited formation of inhibitors. In this work, four H2O2-involved pretreatment methods were assessed for their technical feasibility of biomass pretreatment. Considering the variations of the occurred chemical reactions and the mechanisms on deconstruction of recalcitrant lignocellulose structure, the pretreatment conditions were carefully tailored/optimized to make them more comparable. The pretreatment efficacy was evaluated by comparing cellulose recovery, substrate saccharification rate, enzymatic accessibility etc. These four H2O2-involved pretreatments, i.e., concentrated H3PO4 plus H2O2 (PHP), H2O2–CH3COOH (HPAC), alkaline-H2O2 (AHP) and Fenton-chemistry (FC) were comparatively investigated on wheat straw, poplar, and birch biomass. HPAC displayed excellent delignification performances of 70.3-95.3%, resulting in efficient enzymatic hydrolysis of 77.4-87.5% with a corresponding glucose yield of 255.7-329.7 mg/g feedstocks. Although PHP exhibited lower delignification extent (64.3-93.9%) than HPAC, a considerable high amount of hemicellulose (91%) was removed, and 90-100% enzymatic hydrolysis was achieved. Delignification of 28.8-49.3% was obtained for AHP, but its hemicellulose removal was not efficient. Consequently, enzymatic hydrolysis of AHP-pretreated substrates only reached 24.2-67.8%. After FC pretreatment, the resulting solid only achieved 13.0-37.6% enzymatic hydrolysis, which was close to that of unpretreated feedstocks. Further analysis indicated their high delignification extents correlated to the enhanced enzyme accessibility and enzymatic hydrolysis (R2=0.70). These results suggested that among the four H2O2-involved pretreatments, the one with high deconstruction effect and delignification efficacy was more feasible for biomass pretreatment.