Liquor recycling of oxidative-organosolv pretreatment of maize cob and lignin recovery

Pretreatment is a major step that leads to 18–20% of total expense in the whole bioethanol process; however, it is a mandatory step to break the matrix of lignocellulosic biomasses, improving the cellulosic conversion. Additionally, it must also maintain the quality of the other components of biomass, allowing the valorization of multiple products. Therefore, the present study investigated liquor recycling in the pretreatment of maize cob and the recovery of lignins from the pretreatment and enzymatic hydrolysis. The oxidative-organosolv pretreatment allowed the cellulose-rich biomass and a high sugar release. The pretreatments carried out with full replacement of the components in 50% of the reagent solution correspond to the same performance of the pretreatment with 100% of fresh components, even after three cycles of recycling. When persulfate and H 2 SO 4 were not added, liquor recycling was not a good option. Recycling liquor slightly affected the characteristics of lignin recovered from pretreatment, mainly the thermostability and the capacity to absorb UV radiation. Enzymatic hydrolysis lignin (EHL) showed lower solubility in ethanol and greater capacity to absorb UV radiation than lignin from pretreatment. Thus, the methodology described in this study provides an efficient recycling of liquor in pretreatment, allowing the obtention of value-added products from maize cob. Graphical abstract