Modeling and Statistical Optimization of Dilute Acid Hydrolysis of Eucalyptus Wood Chips using Response Surface Methodology.

Dilute acid hydrolysis was applied for the pretreatment of eucalyptus wood chips to produce fermentable sugars. Chemical composition analysis of the wood chips revealed that the major components of the lignocellulosic material were cellulose, hemicellulose, and lignin (klason and acid soluble) accounting for 42.3, 15.2 and 24.1% respectively. A four variable central composite design for response surface methodology (RSM) was employed to evaluate the simultaneous effect of acid concentration, hydrolysis temperature, hydrolysis time, and liquid to solid ratio on the total reducing sugar concentration obtained during acid hydrolysis of eucalyptus wood chips. A validated quadratic statistical model was developed to relate the hydrolysis variables to the total sugar concentration. The optimal conditions of hydrolysis as obtained from RSM were as follows: acid concentration 0.59%w/w, hydrolysis temperature 130 o C, hydrolysis time 25 minutes and liquid to solid ratio 22.5 mL/g. Under these conditions, the maximum concentration of total reducing sugar was obtained to be 20.6 g/L. Validation of the model indicated no difference between predicted and observed values.