Optimization of pH as a strategy to improve enzymatic saccharification of wheat straw for enhancing bioethanol production

In this work, wheat straw (WS) was used as a lignocellulosic substrate to investigate the influence of pH on enzymatic saccharification. The optimum enzymatic hydrolysis occurred at pH range 5.8-6.0, instead of 4.8-5.0 as has been widely reported in research. Two enzymes cocktails, Celluclast (R) 1.5 L with Novozymes 188, Cellic (R) CTec2 and endo-1,4-beta-xylanase, were used for the pH investigation over a pH range of 3.0-7.0. The highest concentration of total reduced sugar was found at pH 6.0 for all the different enzymes used in this study. The total reduced sugar produced from the enzymatic saccharification at pH 6.0 was found to be 7.0, 7.4, and 10.8 (g L-1) for Celluclast (R) 1.5 L with Novozymes 188, endo-1,4-beta-xylanase and Cellic (R) CTec2, respectively. By increasing the pH from 4.8 to 6.0, the total reduced sugar yield increased by 25% for Celluclast (R) 1.5 L with Novozymes 188 and endo-1 4-beta-xylanase and 21% for Cellic (R) CTec2. The results from this study indicate that WS hydrolysis can be improved significantly by elevating the pH at which the reaction occurs to the range of 5.8 to 6.0.