Process Optimization for Deep Eutectic Solvent Pretreatment of Water Hyacinth for Efficient Enzymatic Saccharification

Water hyacinth is an invasive aquatic species that causes severe ecological disruption but can serve as a promising lignocellulosic feedstock for bioenergy production. In this study, a deep eutectic solvent (DES) system based on choline chloride and formic acid (ChCl/FA) was applied to improve pretreatment efficiency and enhance enzymatic saccharification. Process variables were optimized using response surface methodology (RSM) coupled with a Box–Behnken design (BBD), considering temperature, reaction time, and solid-to-liquid ratio. A quadratic regression model adequately described the relationship between these variables and reducing sugar yield, exhibiting a high coefficient of determination. Optimal conditions were identified at approximately 91.85 °C, 60.70 min, and an S/L ratio of 1:5.07, corresponding to a predicted sugar yield of 0.21 g/g. Experimental validation showed good agreement with model predictions. The findings confirm that ChCl/FA is an effective and environmentally benign solvent for biomass pretreatment and highlight its potential application in sustainable biorefinery processes.