Abstract:
There is a necessity to produce alternative types of fuel that are renewable and eco friendly, since fossil fuel resources are limited. The production of bioethanol from
natural sources such as fruit juice could be one such alternative. The current study was
aimed at determining the potential of using sour orange juice to produce ethanol and
optimizing the conditions to increase the yield. Sour orange juice was inoculated with
Saccharomyces cerevisiae from baker’s yeast in a fermentation media composed of 100
g/L sucrose, 5 g/L yeast extract, 10 g/L KH2PO4, 2 g/L (NH4)2SO4, and 0.5 g/L MgSO4·7H2O
in order to produce ethanol. Ethanol content produced from fermented orange juice
was measured by an Ebulliometer. Initially the amount of ethanol produced from the
orange juice was 5% (v/v) at room temperature (30±2 °C) after 24 h of fermentation.
Then different fermentation times (24,48,72,96 and 120 h), inoculum sizes (0.5,1.0, 1.5
and 2.0 g/100 mL), temperature (25, 30 and 35 °C) and pH (4,5,6 and 7) were used to
find out the optimum culture conditions to produce higher percentage of ethanol from
the juice. After the optimization of culture conditions such as fermentation time (24 h),
inoculum size (1.5 g/100 mL), temperature (30±2 °C) and pH (5.0), the production of
ethanol increased to 6% (v/v). When sucrose was replaced by different carbon sources
such as glucose, maltose, and lactose in the fermentation media, the highest amount of
ethanol production (6.5%, v/v) was obtained in orange juice media with maltose as the
C source. When (NH4)2SO4 was replaced by different nitrogen sources such as,
ammonium nitrate, ammonium chloride and urea in the fermentation media, the
amount of ethanol production was significantly increased to 9% (v/v) in the orange juice
media with ammonium nitrate. The current study concludes that 9% (v/v) ethanol can
be produced from sour orange juice using baker’s yeast under optimized conditions
including maltose as the C source and ammonium nitrate as the N source. A large scale
fermentation study should be carried out in a bioreactor to determine whether this
finding could be commercialized.
