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 pretreatment 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 pretreated 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 H2SO4 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.