3.2. Effects of acid concentration and time
The effect of acid concentration and time on the yield of sugar is
shown in Fig. 2. It was found that with higher levels of acid concentration
and time, the production of ethanol yield level
decreased because it has an effect on the hydrolysis treatment. At a
lower acid concentration and time, the cellulose might not hydrolyse
to simple glucose, and with a higher acid concentration and
time, the cellulose might convert to other molecules that may not
be fermentable [20,21]. Hence, both acid concentration and time
have a strong relationship for the yield of ethanol production. The
results identified well-defined optimum operating conditionsHydrolysis time increases at lower acid concentrations and the
increased level of acid concentration and lower level of time gives a
positive effect on the yield of ethanol. The response surface suggests
that there were dominant interactions of these two factors.
This result is also similar to the experiment that was performed for
the ethanol production from turnip, papaya, and apple and yield of
ethanol, which obtained 1.5% (v/v) [22].