Citation
Rosdi, Anis Nurdhiani
(2021)
Sub-critical water extraction of fucoidan from brown algae Padina sp.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
Chemical, mechanical, and biological approaches are the common extraction
techniques used to extract bioactive compounds. These techniques use
chemical solvents, have long processing steps, and produce low yields. An
important aspect being considered in extracting bioactive compounds is fast
extraction techniques and environmentally friendly extraction processes. One of
the emerging green extraction processes is called Subcritical Water (Sub-CW)
Extraction. The advantages of this technique include significant reduction of
solvents, non-toxic green solvent (water), higher extraction yields, less extraction
time, and low costs of extracting agents.
This study investigates the extraction of fucoidan compounds in brown algae
using Sub-CW technology. The study covers screening and optimizing Sub-CW
parameters, evaluating the process kinetics and thermodynamics, and
comparing the yield of fucoidan with the conventional methods. The presence of
fucoidan was confirmed by running the standard fucoidan using high
performance liquid chromatography (HPLC), and the biomass was further
analyzed using standard analytical instruments. Several analyses have been
done to support the HPLC results. The samples were characterized with Fouriertransform
infrared (FTIR) spectroscopy, scanning electron microscopy (SEM),
and elemental analyzer CHNS to identify the -SO3H functional group and other
organic compounds, surface morphology, and elemental analysis accordingly.
The effect of three different variables, which were temperature, reaction time,
and biomass concentration, were investigated according to a single factor to
achieve maximum fucoidan yield. The result showed that the highest extraction
yield was achieved at 180°C, 10 min extraction, and 2 % biomass concentration.
In the optimization study, the Sub-CW was carried out based on the data generated from central composite design (CCD) by varying different process
parameters, including reaction temperature, reaction time, and biomass
concentration. The experimental range and levels of the independent process
variable were set based on the parameters from the screening experiment. The
optimum fucoidan of 50.65 wt% was achieved at 176 °C,12 min, and a
concentration of 2%. A single, consecutive reaction model used for data
validation showed a good agreement between the experimental and theoretical
data generated.
In terms of the kinetic and thermodynamic behavior of fucoidan extraction from
brown algae by Sub-CW, it was observed that the fucoidan yield could be rapidly
produced and decomposed from the subcritical water extraction process.
Thermodynamic analysis by transition-state theory showed the subcritical water
reaction process as endothermic, while the Gibbs free energy of activation
showed the reaction as non-spontaneous, requiring constant external energy to
support it.
Overall, this study shows the capability of Sub-CW in extracting fucoidan from
brown algae. Thus, the findings will benefit the food and pharmaceutical
industries to utilize a green method for extracting biomolecules from macroalgae
for new products with high added value.
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