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 H₂O_2  (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 H₂SO_4  was optimized by varying the  concentrations of H₂SO_4  (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 H₂SO_4 concentration  (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.