Combination of acid pretreatment with ultrasonic before enzyme treatment increased
the conversion of lignocelluloses to sugar. Sugar yield up to 44% w/w after combination of acid and
ultrasonic pretreatment and subsequent enzyme treatment could be achieved. Fermentation of
pretreated rice straw shown that after 3 days fermentation most of sugar (55-65%) will be converted to
bioethanol. The remaining sugar could not be converted in ethanol even after 6 days fermentation.
Under these conditions, the maximum ethanol of 1.69% (v/v) was obtained