Estudo do pré-tratamento de bagaço de cana-de-açúcar e sabugo de milho assistido por ultrassom e micro-ondas utilizando solventes eutéticos profundos

Abstract

The growing interest in alternative sustainable energy sources has driven research into biofuel production from agro-industrial residues. Second-generation (2G) ethanol, derived from lignocellulosic biomass, emerges as a promising alternative due to its lower environmental impact and non-competition with food production. This study evaluated the potential of sugarcane bagasse and maize cob for ethanol production after microwave-assisted (15 min, 110–150ºC) and ultrasound (10 min) pretreatment using deep eutectic solvents (DES). The systems used were Choline Chloride with Lactic Acid (ChCl: Lactic Acid) and Choline Chloride with Glycerol (ChCl: Glycerol) in a 1:2 ratio. The pretreatments promoted substantial lignin and hemicellulose removal, with ChCl: Glycerol achieving the highest delignification rates of 73.23% for sugarcane bagasse and 75.79% for maize cob. Significant enrichment of the cellulose fraction was observed, increasing cellulose availability up to 74.57% in sugarcane bagasse (ChCl: Lactic Acid) and 53.69% in maize cob (ChCl: Lactic Acid). XRD, FTIR, and SEM analyses confirmed increased porosity and crystallinity index, indicating efficient removal of amorphous components and preservation of cellulose type I. In the fed-batch enzymatic hydrolysis step, high solid loading enhanced sugar release, with bagasse treated with glycerol reaching 112.15 g/L of total reducing sugars (TRS) using ChCl: Glycerol. Alcoholic fermentation with Saccharomyces cerevisiae showed rapid glucose consumption within the first 24 h, with maximum initial productivity of 2.44 g/L for sugarcane bagasse and 1.29 g/L for maize cob pretreated with ChCl: Glycerol. These results indicate that the use of DES, especially ChCl: Glycerol, combined with ultrasonic and microwave treatment, is a highly effective and sustainable route for valorizing agro-industrial residues in 2G ethanol production.