Corn residues are an abundant and low-cost lignocellulosic feedstock that provides a renewable carbon platform for the production of biofuels, bioplastics, and high-value aromatic volatile compounds (AVCs). Isoamyl alcohol, an important AVC, has applications in the food, cosmetics, and biofuel industries. This study evaluated the bioconversion of corn cob acid hydrolysates by Meyerozyma guilliermondii into isoamyl alcohol and ethanol. Corn cob was selected as feedstock due to its high hemicellulose content. A Box–Behnken (BBD) design was used to optimize phosphoric acid hydrolysis. The optimal treatment (2.49% v/v H₃PO₄, 130 °C, 120 min, 1 mm particle size) generated 19.79 g L⁻¹ xylose with 2.74 g L⁻¹ acetic acid. Then, agitation speed and nitrogen concentration were optimized via a central composite design (CCD) in synthetic and hydrolysate-based media fermentations. Isoamyl alcohol specific yield after 48 h of fermentation was higher in hydrolysate medium (12.08 ± 0.67 mg·g⁻¹) than in synthetic medium (8.274 ± 0.83 mg·g⁻¹). Free amino nitrogen (FAN) and intracellular protein analyses revealed higher nitrogen consumption in synthetic media fermentation and greater biomass production in acid hydrolysate media. In addition to isoamyl alcohol (33 mg·L⁻¹), and ethanol (10.18 g·L⁻¹), 1-butanol (61.2 mg·L⁻¹), 1-propanol (13.25 mg·L⁻¹), and acetaldehyde (14.88 mg·L⁻¹) were produced. These results demonstrate the potential of M. guilliermondii to convert corn cob into value-added products.

Efficient pretreatment is essential for overcoming lignocellulosic biomass recalcitrance and enabling its use in biotechnological processes. In this study, corncob, an agricultural by-product rich in cellulose and hemicellulose, was subjected to acid pretreatment to remove hemicellulose and subsequently delignified using two deep eutectic solvent (DES) systems: choline chloride:urea and choline chloride:glycerol. The effect of temperature and reaction time was evaluated for both systems; ChCl:U was selected for optimization due to its superior lignin removal performance under the conditions evaluated. Temperature, time, and solid–liquid ratio (SLR) were optimized using a Box–Behnken design to maximize lignin removal. Under optimal conditions (113 °C, 5.7 h, 1:16.2 g/mL), 59.086% lignin removal was achieved. Temperature and reaction time significantly influenced delignification, whereas the solid–liquid ratio had a minimal effect. Structural changes in biomass throughout the process were characterized by compositional analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), confirming effective delignification. To the best of our knowledge, there are few studies that comprehensively characterize DES-treated corncob using FTIR and SEM analysis. These findings demonstrate that choline chloride:urea has potential as a sustainable and effective pretreatment system for lignocellulosic biorefineries based on agricultural residues.