Abstract
Sugarcane bagasse is the major by-product of the sugarcane industry and, due to its abundant availability, it has been extensively studied for lignocellulosic bioconversion in the production of bioethanol and other value-added commercial products. In the study presented herein, a combined pretreatment using sulfolane, TiO2 and alkali microwave irradiation (MW-A) was assessed for the dissolution of lignin prior to enzymatic saccharification of holocellulose. Total reducing sugars (TRS) and saccharinic acid yields were investigated. The increase in NaOH concentration up to 5% and in temperature from 120 °C to 140 °C were found to have a positive influence on both yields. While increasing the reaction time from 5 to 60 min only led to an increase in TRS yield <2%, a reaction time of 30 min almost doubled the saccharinic acids production. TRS yields and saccharinic acid production were approximately 5% and 33% higher when the sulfolane-TiO2 reaction medium was used, as compared to MW-A in water, reaching up to 64.8% and 15.24 g/L of saccharinic acids, respectively. The proposed MW-A pretreatment may hold promise for industrial applications, given the good TRS yields obtained, and the associated enzyme and time/energy savings. The use of sulfolane-TiO2 reaction medium is encouraged if saccharinic acids are to be recovered too.
Highlights
In recent decades, several strategies for the valorization of biomass and its associated waste have been extensively researched for the production of energy and bioproducts
Both pretreated and treated residues exhibited a peak at around 2900 cm−1, which indicates -CH2 stretching; a peak at 897 cm−1, which indicates β-glucosidic linkages; and a strong band at 1031 cm−1, attributed to C–O–C stretching from cellulose and hemicelluloses [31]
The use of sulfolane-TiO2 in combination with alkali microwave irradiation (MWI) pretreatment was assessed on sugarcane bagasse (SCB)
Summary
Several strategies for the valorization of biomass and its associated waste have been extensively researched for the production of energy and bioproducts. In this context, second-generation (2G) bioethanol from lignocellulosic biomass as a raw material has gained interest in the development and application of sustainable technologies [1]. Three steps are required: (i) a pretreatment, which converts the recalcitrant lignocellulosic structure into cellulosic and hemicellulosic intermediates;. One of the most challenging stages in the second-generation ethanol production process is the pretreatment (dissolution of lignin) prior to enzymatic saccharification of holocellulose [3]
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