Screening And Characterization Of Starch Produced From Marine Microalgae Klebsormidium Flaccidum Gn-2
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Date
2021-03
Authors
Ramli, Rozi Nuraika
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Starch is the main component that belongs to two third of the human diet
pyramid and another one third of starch is used in non-food applications such as biofuel
and bioplastic. Products produced from starch are biodegradable and help in reducing
the environment pollution. However, environmental problem such as deforestation and
shortage of food will eventually happen if the demands of starch from non-food and
food products increase. Simultaneously, crops using as feedstocks for biofuel will
result in food versus fuel implication. To resolve this problem, the attentions of
researchers have been driven towards microalgae. The easy growing and
environmentally friendly microalgae has opened a new potential of revolution for
starch-based product. In this research two strains of marine microalgae have been
successfully isolated and screened from Penang Sea. Based on morphological and
molecular identification, these 2 strains are designated as Klebsormidium flaccidum
GN-2 and Nannochloropsis oculata YG-2. K. flaccidum GN-2 produced 16.84% of
starch and 0.81 g/L biomass while, N. oculata YG-2 produced 3.06% and 0.40 g/L
ofstarch and biomass, respectively. Microalgae K. flaccidum GN-2 was chosen for
optimization using Response Surface Methodology (RSM) to increase production of
starch since it yield higher starch than Nannochloropsis oculata YG-2. The starch
produced was 19.06% under the optimized conditions of 35.53 ppt salinity, 23 hours
of light exposure and flow rate of 1 v/v of carbon dioxide. The nutrient optimization
was studied based on depletion of nitrogen (N), phosphorus (P) and iron (Fe) as the nutrient depletion will change the physiochemical of the microalgae. Decreasing of
biomass (N = 0.98 g/L, P = 0.22 g/L and Fe = 0.24 g/L) and starch (N = 6.39%, P =
4.62%, Fe = 4.46%) however illustrated that depletion of the nutrients in K. flaccidum
GN-2 could not increase the starch content. The starch was characterized and
compared with commercial corn starch (CCS) for its properties. Small granule (1 μm)
and high amylose content (25.52%) in K. flaccidum GN-2 were compared to
commercial corn starch (size 7 μm, amylose 23.04%) suggested that starch from K.
flaccidum GN-2 as the best potential feedstock for strong and stiffer films due to small
size of granule. Gelatinization of starch from K. flaccidum GN-2 is lower (ΔHgel =
9.45 J/g) than commercial corn starch (ΔHgel = 11.63 J/g). This is due to the lower
amylopectin content in K. flaccidum GN-2 leads to lower crystallinity and less energy
needed to dissociate the molecule within the granule. The retrogradation and syneresis
results showed that microalgae starch contains similar stability with CCS as the
gelatinized starch able to reassociate to form more ordered structure within 72 hours
and completely ageing after 3rd cycle like CCS. In conclusion, marine microalgae
isolated from Penang Sea was successfully produced starch. Even though the
optimized starch did not show significant increased, however the characteristics
studied in starch from K. flaccidum GN-2 is comparable to the CCS starch. Hence it
could be an alternative to produce various sustainable products that least compete with
crops starch.
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