Comparison of pretreatment strategies for the integrated production of pectin and fermentable sugars from cocoa pod husk within a biorefinery approach

The valorization of cocoa pod husk (CPH) within a circular bioeconomy framework is essential to address the underutilization of this abundant agro-industrial residue. This study evaluated four pretreatment strategies (citric acid, alkaline, protic ionic liquid, and hydrothermal) aimed at simultaneously extracting pectin and enhancing biomass suitability for fermentable sugar production. A Design of Experiments approach based on Response Surface Methodology was employed to assess the effectiveness of pretreatments in pectin extraction, acetyl group removal, and modification of biomass composition (cellulose, hemicellulose, and lignin contents). Pretreated biomasses were subjected to sequential acid and enzymatic hydrolysis. Kinetic and compositional analyses demonstrated that all pretreatments promoted pectin extraction (9.9%–13.1%), increased sugar release by at least 5%, and reduced total phenolics and acetic acid concentrations by at least 30% and 55%, respectively. Moreover, pretreatments significantly decreased hydrolysate viscosity and improved biomass processability. Citric acid pretreatment achieved the highest sugar recovery (8.8 kg 100 kg −1 dry CPH), followed by protic ionic liquid, alkaline, and hydrothermal pretreatments (7.9, 6.9, and 5.8 kg 100 kg −1 dry CPH, respectively). Hydrolysates obtained from pretreated CPH exhibited higher sugar consumption rates and yields, providing improved suitability for xylitol and arabitol production by Candida tropicalis . Overall, these findings demonstrate the potential of integrated pretreatment strategies to enhance CPH valorization, supporting its application as a promising feedstock for the production of value-added bioproducts in biotechnological processes.