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In this work, the combined pretreatment of sulfuric acid and alkaline (SA), solid acid and organic solvent (SO) and phosphoric acid and peroxide (PHP) on poplar was used to thoroughly evaluate the effects of wet and dry processing on enzymatic digestibility. The finding showed a negative connection between increasing glucose yield and rising drying temperature. Moreover, research showed that wet processing is beneficial because it improve mass transfer and permeability for enzymatic liquefaction. Enzymatic hydrolysis was additionally increased by mechanical wet milling following combined pretreatment. Most importantly, SO pretreatment was superior to PHP because SO pretreatment had a stronger linear relationship between particle size and glucose yield. Wet-milled post-treatment followed by SO combined pretreatment produced an acceptable glucose yield (91.93%). In comparison to the untreated poplar, the glucose yield had an increase by 87.14%. This work offers a novel processing method that might serve as a theoretical sound foundation for the effective saccharification of poplar wood. • There were negative correlation between drying temperature and glucose yield. • Wet processing is advantageous on pretreated poplar enzymatic hydrolysis. • SO pretreatment followed by wet-millied process made a glucose yield of 91.93%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crystallization stress by ice expansion in biomass pores was modeled. • The stress by freeze pretreatment was calculated as 22.5–38.3 MPa at −20– −40 °C. • Specific surface area of rice straw increased by 1.2-fold after pretreatment. • Combined pretreatment achieved 97.2% cellulose recovery & 72% lignin removal. • Glucose yield via hydrolysis rose to 91.1% by 4.3 times that for original straw. Freeze pretreatment combined with alkaline-hydrothermal method of rice straw for enzymatic hydrolysis was studied. Crystallization stress in the rice stem pores caused by water freezing at −20– −40 °C was modeled to illustrate the destruction mechanism. The stress was calculated as 22.5–38.3 MPa that were higher than the tensile yield stress of untreated stems (3.0 MPa), indicating ice formation damaging pore structure. After freeze at −20 °C, rice straw was further hydrothermally treated at 190 °C with 0.4 M Na 2 CO 3 , achieving 72.0 % lignin removal and 97.2 % cellulose recovery. Glucose yield rose to 91.1 % by 4.3 times after 24 h hydrolysis at 10 FPU loading of Cellic®CTec2 cellulase. The specific surface area of rice straw was 2.6 m2/g increased by 1.2 times after freeze. Freeze combined with alkaline-hydrothermal treatment is a green and energy-efficient method for improving enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

• A combined pretreatment with polyethylene glycol-epoxides modification was developed. • Effects of molecular weight of modifiers on enzymatic hydrolysis were evaluated. • In-situ modification of lignin boosted enzymatic digestibility of masson pine. • The modification lowered enzyme nonspecific binding and enhanced fiber swelling. Acid pretreatment was insufficient to disrupt the recalcitrance derived from lignins in softwood, thus a lignin-targeting post-treatment was required. In this study, a combined acid and alkali pretreatment with polyethylene glycol-epoxides (PEG-epoxides) was developed on masson pine. Results showed although the combined pretreatment achieved a limited delignification, but a remarkably increment of 15.9–34.9% on hydrolysis yields was achieved. This was ascribed to the successful incorporation of hydrophilic PEG chains to residual lignins. Moreover, the improvement on enzymatic digestibility varied with the PEG chain lengths in modifiers. The underlying reasons for this improvement were primarily investigated by monitoring the lignin properties as well as water retention values variation after in-situ lignin modification by PEG-epoxides with varied molecular weights. It indicated that the enzymatic hydrolysis improvement was mainly due to both reduced enzyme nonspecific adsorption and increased fiber swelling. Results will give new insights to resolve the challenge on softwood biorefinery. [ABSTRACT FROM AUTHOR]