In-situ lignin modification with polyethylene glycol-epoxides to boost enzymatic hydrolysis of combined-pretreated masson pine

Acid pretreatment was insufficient to disrupt the recalcitrance derived from lignins in softwood, thus a lignintargeting 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.