Productivity enhancement of spirulina (Arthrospira platensis) using flexible floating-bed photobioreactor, mixing methods and nitrogen sources
Nowadays, microalgae are becoming the focal point to solve malnutrition or malnourishment, especially in developing countries. Malnutrition significantly causes thousands of deaths especially among children. In Malaysia, mass cultivation of Spirulina has not been well explored. This is due to the...
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Format: | Thesis |
Language: | English |
Published: |
2015
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/68151/1/FS%202015%2052%20IR.pdf |
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Summary: | Nowadays, microalgae are becoming the focal point to solve malnutrition or
malnourishment, especially in developing countries. Malnutrition significantly
causes thousands of deaths especially among children. In Malaysia, mass cultivation
of Spirulina has not been well explored. This is due to the lack of information and
scientific data pertaining to Spirulina cultivation under Malaysian climate.
Therefore, the aim of this study was to develop a new culture system for Spirulina
mass cultivation. The study was conducted under outdoor condition settings.
Arthrospira platensis was cultured inside flexible floating-bed photobioreactor
whereas land based photobioreactor was established as control. Half concentration of
standard Kosaric medium from the original amount was used in this study. Both
physical and growth parameters were determined daily while the nutritional content
was determined at day-8 for cycles I, II and III. The pH variations recorded normal
ascending patterns throughout the cultivation period. No significant difference (p >
0.05) of dissolved oxygen concentrations was found, however, land based
photobioreactor showed slightly higher reading on average. A significantly higher (p
< 0.05) culture temperature recorded inside land based photobioreactor was 32.97 ±
0.50 ºC, while the culture temperature inside flexible floating-bed was 28.97 ± 1.40
ºC. No significant difference (p > 0.05) of total chlorophyll and biomass variations
were observed. Both flexible floating-bed and land based photobioreactors showed
no significant difference in terms of protein content (p > 0.05) but recorded higher
protein content of more than 45% of 1 g cell dry weight. Both photobioreactors
recorded lower lipid content of not more than 1.5% of 1 g cell dry weight.
Subsequently, in outdoor environment and half strength of media concentration, A.
platensis was cultured inside flexible floating-bed photobioreactor with different
mixing methods namely aeration and agitation. Aeration mixing recorded significantly lower (p < 0.05) dissolved oxygen concentrations. Lower values of
temperature were also recorded (p < 0.05) between flexible floating-bed
photobioreactor with aeration and land based photobioreactor. Arthrospira platensis
with aeration mixing contained significantly more (p < 0.05) total chlorophyll
content. Biomass concentration also revealed higher values (p < 0.05) for aeration
mixing compared to agitation mixing. Major differences were observed for many
parameters as higher dissolved oxygen concentration inhibits cell growth
significantly. On average, protein content was higher (p < 0.05) in aeration mixing
up to 46.57 ± 1.53%, compared to agitation at 22.47 ± 2.17%. Vice versa, agitation
mixing recorded significantly higher (p < 0.05) carbohydrate content compared to
aeration mixing. No significant difference (p > 0.05) was recorded for lipid content.
Specific growth rate recorded for aeration was 0.223 1/day while for agitation was
0.121 1/day.
Both NaNO3 and CH4N2O displayed promising growth performance of A. platensis
for outdoor cultivation inside flexible floating-bed photobioreactor. No significant
difference (p > 0.05) of optical density, total chlorophyll content and biomass
concentration was recorded between the two different nitrogen sources for outdoor
cultivation. However, optical density and total chlorophyll recorded slightly higher
readings for NaNO3 due to the nitrogen atom being readily able to be used by the cell
in culture media compared to CH4N2O. Cultivation with NaNO3 as nitrogen source
revealed significantly higher (p < 0.05) protein content up to 46.57 ± 1.53%.
Meanwhile, CH4N2O recorded lower protein content but the synthesis of
carbohydrate content was significantly higher, up to 48.08 ± 1.27%. The specific
growth rate of NaNO3 was 0.223 1/day better than CH4N2O.
The study indicated higher growth in flexible floating-bed with aeration. NaNO3 was
better than CH4N2O. Bio-economic study has determined that the compound,
CH4N2O is more cost effective as it is cheaper and readily available in the market. |
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