Optimization of Pre-treatment Process of Cocoa Pod Husk Using Various Chemical Solvents

Abstract

The purpose of research is to see the effect of type of reagent (NaOH, H₂O₂ and H₂SO₄) and the condition of pre-treatment of cocoa pod husk towards lignin content after pre-treatment and hydrolysis, reducing sugar and total sugar content. Response Surface Method (RSM) was used to optimize process conditions of pre-treatment (delignification). Hydrolysis for all pre-treated sample were carried out using 3% H₂SO₄ with a ratio of cocoa pod husk to solvent (1:10) for 2 hours at a temperature of 110 ^oC using an autoclave. The chemical pre-treatment with NaOH was optimized by varying the concentrations of NaOH (4-8% (w/v), centre point: 6%), reaction time (60-100 minutes, centre point: 80 minutes) and ratio of biomass to solvent (1:15-1:25, centre point 1:20 w/v). The optimum conditions in this study was at the concentration of NaOH (X₁) of 4% w/v, reaction time (X₂) of 100 minutes; ratio of biomass/solvent (X₃) of 1:25 (w/v). The lignin content after pre-treatment was 15.03% lignin, lignin content after hydrolysis was 19.57%, 11.75% of reducing sugar, and 12.78% of total sugar. The chemical pre-treatment with alkaline peroxide (H₂O₂) was optimized by varying the concentrations of H₂O₂ (4-7% w/v, centre point 5.5% (w/v)), reaction time (40-90 minutes, centre point: 65 minutes), and ratio of biomass/solvent (4-7% w/v). The optimum conditions in this study was at the concentration of H₂O₂ concentration (X₁) of 5.52% w/v, reaction time (X₂) of 61.97 minutes, biomass loading in solvent (X₃) 7% w/v. The lignin content after pre-treatment was 8.759, lignin content after hydrolysis was 25.029%, 8.169% of reducing sugar, and 10.371% of total sugar. The chemical pre-treatment with H₂SO₄ was optimized by varying the concentrations of H₂SO₄ (0.5-1.5% w/v), reaction time (60-120 minutes, centre point: 90 minutes), and ratio of biomass to solvent (1:4-1:6 w/v, centre point 1:5 w/v). The optimum conditions was reached without hydrolysis. The optimum condition this study is at the H₂SO₄concentration (X₁) of 1.5%, reaction time (X₂) of 120 minutes, ratio of biomass/solvent (X₃) of 6%. The lignin content after pre-treatment was 18.8%, 15.59% of reducing sugar and 20.49% of total sugar.