Biosynthesis of carbohydrate and lipid in Chlorella vulgaris UPSI-JRM01 for biofuel feedstock production
<p>This study aims to investigate the effect of photo-autotrophic cultural conditions (light intensity, temperature, pH, CO2 and NO3-) of C. vulgaris UPSI-JRM01 and to optimise the lipid, carbohydrate and biomass productivities for high biofuel feedstock production. In addition, carbon...
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| Format: | thesis |
| Language: | eng |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://ir.upsi.edu.my/detailsg.php?det=8575 |
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| Summary: | <p>This study aims to investigate the effect of photo-autotrophic cultural conditions (light intensity, temperature, pH, CO2 and NO3-) of C. vulgaris UPSI-JRM01 and to optimise the lipid, carbohydrate and biomass productivities for high biofuel feedstock production. In addition, carbon partitioning mechanism under nitrogen stress was also elucidated. The method of single-factor experiment was used to determine the effect of each cultural condition. The optimisation process was performed using statistical method of Plackett-Burman Design and Central Composite Design. The whole transcriptome analysis of gene expression under nitrogen stress was also performed using RNA sequencing. The results indicated that the lipid and carbohydrate yields were increased 3.19-fold and 1.39-fold under nitrogen stress and 5% CO2, respectively. The highest biomass productivity was achieved at 10,500 lux, 28 oC, pH 8, 5% CO2 and 500 mg/L NO3-. Meanwhile, the highest lipid yield was achieved at 23,500 lux, 40 oC, pH 8, 0.03% CO2 and without NO3- addition. The biomass, lipid and carbohydrate productivities were optimised to 404.24 mg/L/day, 65.30 mg/L/day and 165.43 mg/L/day, respectively. The major fatty acid methyl ester components were C16:0 (33.54%) and C18:2 (30.29%), thereby producing biodiesel complied with ASTM D6751 standard. Moreover, the results of gene expression study revealed the two-stage response to nitrogen stress; i) carbohydrate accumulation, plastid protein degradation, and amino acid biosynthesis, and ii) lipid accumulation, carbohydrate degradation, and DNA damage. In conclusion, the production of biofuel feedstock from microalgae biomass was feasible. The nitrogen stress triggered high carbohydrate accumulation before the carbon partitioned into triacylglycerol (TAG) using two different pathways; chloroplastic TAG synthesis and glycerolipid metabolism. The implication of this study can be associated with the potential development of biofuel feedstock from microalgae for future application and providing insight of carbon partitioning mechanism in C. vulgaris UPSI-JRM01 under nitrogen stress.</p> |
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