Enhancement in sugar extraction from Pistia stratiotes through statistical optimization of alkaline pre-treatment and enzymatic hydrolysis

In lignocellulosic biomass, reducing structural recalcitrance and enhancing hydrolysis efficiency are crucial factors for increasing fermentable sugars and the production of valuable products. This biomass substrate comprises lignin, hemicellulose, and cellulose. In this study, response surface methodology was employed to optimise alkaline pre-treatment followed by enzymatic hydrolysis, aiming to enhance the saccharification of Pistia stratiotes. The NaOH concentration during pre-treatment significantly influenced the delignification process, resulting in increased cellulose content. The highest cellulose content was achieved with 2.47% NaOH at 120 °C for 60 min, leading to enhanced cell porosity and facilitating greater enzyme saccharification accessibility. Under these optimized conditions, the sample exhibited a 51.66% cellulose content. The physicochemical characteristics of the cellulose obtained after pre-treatment were analysed using SEM, FTIR, and TGA. After enzymatic hydrolysis of the cellulose with a commercially available cellulase enzyme, 31.06 g/L of reduced sugar was produced after 72 h. This study demonstrates that alkaline pre-treatment of Pistia stratiotes significantly increased its cellulose content, leading to a higher sugar yield during enzymatic hydrolysis.