Optimized Enzymatic Bioconversion of Palm Kernel Meal to a Mannose-Rich Syrup

Palm kernel cake (PKC), a byproduct of palm kernel oil extraction, is processed into palm kernel meal (PKM), which contains hemicellulose rich in mannose, a versatile sugar with applications in the pharmaceutical and food industries. However, its association within the lignin–cellulose matrix is a challenge for industrial extraction. This study proposes an optimized enzymatic hydrolysis method utilizing mannanase to maximize the mannose content from PKM powder to produce palm kernel mannose syrup. A 33 Box–Behnken design within a response surface methodology coupled with a desirability function method was used to optimize hydrolysis parameters to maximize mannose and solids content while minimizing enzyme concentration and hydrolysis time. The optimal conditions for enzymatic hydrolysis were established as a reaction time of 16 h, 5% (w/v) solids, and 5% (w/w) enzyme, resulting in 4.325 g/L of mannose and a mannose yield of 24.33 ± 0.5%. The palm kernel mannose syrup was evaluated, resulting in a moisture content of 15.85 ± 0.07%, water activity of 0.6918 ± 0.003, and a pH of 4.05 ± 0.282, demonstrating shelf-life stability. These findings demonstrate the technical feasibility of valorizing PKC and PKM into a stable, mannose-rich syrup, offering a sustainable and scalable pathway for converting agro-industrial waste into high-value ingredients for multiple value-added applications.