Modeling and Optimization of Reducing Sugar Concentration of SternEnzym
Hydrolyzed Fruit Peels via Response Surface Methodology.
Abstract
Processing of fruits in Ghana leads to the generation of tonnes of waste
such as peels, seeds, cores and crowns. Handling this waste tends to be
a major challenge. The usual practice is to discard these wastes in
drainages, water bodies and in landfills. However, if these wastes are
used as feedstock to produce enzymes, bioethanol, and specialty
chemicals instead of being dumped in landfills or put in the ocean, this
unwanted environmental pollution can be avoided. Utilizing these wastes
as a resource for energy production such as bioethanol, which is
produced from the fermentation of reducing sugars is a means of
addressing the sanitation issue while valorizing the waste. The main aim
of this work was to use Response Surface Methodology, to estimate
conditions for the optimal production of reducing sugars from fruit
wastes via hydrolysis using enzymes. The substrate used compromised of
pineapple peels, pawpaw peels, mango peels and a blend of these three
fruit peels. Fruit waste samples were pulverized and aliquots of 2.5%
w/v, 5% w/v, 6% w/v and 7.5% w/v substrate concentration made for
analyses. Fruit waste samples were saccharified with commercial enzyme
procured from the market and samples taken from 12 to 72 hours to
determine reducing sugar yield. Central Composite Design, a statistical
design tool in Response Surface Methodology was used to investigate the
effect of two significant independent variables, hydrolysis time and
substrate concentration on the response variable, reducing sugar yield
in the hydrolysis process. Results indicated that cellulose and
hemicellulose were highest in pawpaw peels, 25.8% and 25.1%,
respectively. Saccharification with commercial enzymes showed that blend
had the highest concentration of reducing sugars at 7.5% substrate
concentration after 48 hours. Optimisation of process parameters gave
optimal conditions for pineapple peels to be time of 32.8 hours,
substrate concentration of 3.5% w/v, TRS yield of 16.6 mg/mL. That of
mango were optimal time of 34.2 hours, substrate concentration of 4.7%
w/v, a TRS yield of 27.8 mg/mL. Pawpaw peel had optimal conditions of
67.6 hours, substrate concentration of 5.1% w/v, TRS yield of 25.5
mg/mL. Peels blend had time of 61.7 hours, substrate concentration of
5.9% w/v and TRS yield of 45.4 mg/mL. These optimal conditions can be
followed for effective hydrolysis of fruit peels while cutting down on
time and cost associated with hydrolysis.