**4. Conclusion**

From this study on optimization of alkaline delignification and enzyme hydrolysis on steam exploded oil palm trunk followed by yeast fermentation to produce ethanol, an encouraging results were obtained. We concluded that delignification of steam explode pulp with NaOH was more influenced than delignification with KOH on term of less alkaline concentration consuming and lower reaction temperature. The comparison enzyme hydrolysis condition for both delignified pulp showed that NaOH delignified pulp gave higher the percentage of glucose yield than KOH delignified pulp. After optimizing the both delignification (NaOH and KOH) and both enzyme hydrolysis parameter by RSM, the highest ethanol yield of 65% were obtained from both fermentations with 50 g/l of glucose raw material.

The empirical quadratic models successfully predicted the percentage of glucose in pulp after delignification and the percentage of glucose in hydrolyzed solution after enzyme hydrolysis and they used in the development of better estimation tools. In addition, response surface plot in three-dimension obtained from the empirical quadratic models can show the interaction effect of two variables on the studied response and the optimum values of the selected variables are obtained from response surface plot, too.
