pH is one of the parameters which was used to evaluate the performance of SSF. Fig. 2b shows that SSF carried out at pH 5 to pH 6 generally shows increasing bioethanol yield as the reaction progresses. The bioethanol yields increases linearly and eventually reaches a plateau except for pH 5 where the yield gradually drops after it reaches a peak at 93.76%. pH 4.5 shows a lower production rate as compared to the higher pH employed and pH 4.0 gives the lowest bioethanol yield which is less than 20%. The residual sugar measurement carried out as shown in Fig. 2a illustrated that there are no significant sugar left in the medium for pH from 4.5 to 6.0, indicating that the sugar were immediately taken up by the yeast. The HPLC analysis identified a significant amount of fermentable sugar present in medium at pH 4.0, indicating that amyloglucosidase enzyme works well under such acidic condition but the acidic condition becomes an environmental stress for yeast to grow. As a result, the fermentation could not proceed