Optimization of Ethanol Production from Orange Peels using Response Surface Methodology

The factors of high oil price, the need for increased energy security and concern
over greenhouse gas emissions from fossil fuels make bioethanol the focal point of the
public and researchers. Bioethanol is a form of renewable energy that can be produced
from agriculture feedstock. The recent study has come out with a new feedstock for the
production of ethanol, which is using orange peels. The production of ethanol using
orange peels is preferable to be studied due to the existing production method produce a
heavy carbon footprint and also high in cost. Besides, it is also related to the disposal
problem and environment concern as the wastes from processed orange are just left over
and commonly are burnt.
Thus, in this project, research was done to produce ethanol from orange peel using
two stage hydrolysis and fermentation studies, to study the effects of yeast concentration
and temperature on ethanol production from orange peel and to optimize the
concentration of yeast and temperature using Response Surface Methodology (RSM)
method. In order to achieve these objectives, experiment was conducted which
comprises the two stages hydrolysis process, preparation of yeast cells, fermentation and
optimization using RSM.
For the first part of experiment, the primary and secondary hydrolysis of orange
peel was carried out at acid concentration of 0 to 1.0% (w/v). At acid concentration of
0.5 and 0.75% (w/v) was the highest glucose yield for primary and secondary
hydrolysis, respectively. For the fermentation, the range of temperature and yeast
concentration of 30°C to 40°C and 0.1% to 0.5% (w/v) respectively, was selected to be
studied. The pH and fermentation time was fixed at optimum condition which is pH5
and 15h accordingly. Response Surface Methodology (RSM) using two factors and two
level central composite design was employed to optimize the effect of temperature and
yeast concentration on ethanol production from orange peel. Based on the results
obtained, the highest ethanol yield is around 6-6.2 g/L at temperature of 39-40°C and
yeast concentration of 0.25-0.3% (w/v). So, with this finding, it shows promise for scale
up studies for larger industry.