DYNAMICS OF ?-CAROTENE AND FUCOXANTHIN IN TROPICAL MARINE NAVICULA SP. GALUR NLA CELL CULTURED UNDER ENVIRONMENTAL STRESS CONDITIONS

• Main Author: Telussa, Ivonne
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/36074
• Institution: Institut Teknologi Bandung

Tropical marine diatom Navicula sp. galur NLA are able to survive in the extreme environmental conditions, e.g. living under high light exposure by regulating their ?-carotene and fucoxanthin metabolism in cells. Dynamics of ?-carotene and fucoxanthin metabolic pathway in Navicula sp. galur NLA cells cultivated in modified medium in indoors and outdoors conditions were studied to understand how Navicula sp. galur NLA cells overcome environmental stresses such as conditions at high light intensity. So far, research on tropical marine diatoms Navicula sp. galur NLA as a model organism to produce a large scale ?- carotene and fucoxanthin outdoors has yet been conducted. As an organism of microscopic photosynthesis, Navicula sp. galur NLA may grow under direct sunlight exposure in which their daily and seasonal light intensities are fluctuated that reducing biomass productivity, changing cell metabolism, and disturbing photosynthesis, with the result that changing fucoxathin and ?-carotene synthesis pathway. Hence, this research aimed to study the growth of tropical marine diatom Navicula sp. galur NLA in both indoor and outdoor conditions and to understand the dynamics of accumulation of ?-carotene and fucoxanthin. Methods used in this study included three stages. Firstly, Navicula sp. galur NLA cell growth and biomass productivity in premix and modified medium were evaluated. The premix medium was a Walne medium containing rich nutrients, while a modified medium was a simple medium containing a mixture of urea, silicate, iron and phosphate. Secondly, effects of nutrition, growth conditions, and photosynthetic pigment accumulation of Navicula sp. galur NLA under indoor conditions were examined. Nitrogen sources, e.g. urea, nitrate, and ammonium in medium, along with silicate concentration are optimized to obtain high Navicula sp. galur NLA biomass as well as high ?-carotene and fucoxanthin. Accumulation of ?-carotene and fucoxanthin in cells grown in limited nutrients was observed. In addition, effects of light intensities on Navicula sp. galur NLA cell growth as well as ?-carotene and fucoxanthin accumulation were investigated. This was to understand the cell response under light stress. Finally, effects of direct sunlight exposure on Navicula sp. galur NLA cell growth, and the accumulation of ?-carotene and fucoxanthin were evaluated. In this study, determined parameters were biomass productivity, ?-carotene and fucoxanthin content, fucoxanthin/?-carotene ratio, and ?-carotene and fucoxanthin productivity. To get an easily obtainable and inexpensive growth medium, the growth of Navicula sp. galur NLA cells grown in a premix medium compared to that in a modified medium. The results showed that Navicula sp. galur NLA cultured in a modified medium with an initial density of 5 × 106 cell mL?1 grew well with cell density of 13,37 ± 0,2×106 cell mL?1 on 7th d, while the cell density in premix medium was 8,24 ± 0,1×106 cell mL?1. These were equivalent to Navicula sp. galur NLA biomass productivity of 260.8±12 mg dry cells L ?1 h?1 in modified medium and 100.76±0.5 mg dry cells L?1 h?1 in premix medium. So, modified medium with 88.2% lower cost than premix medium was a better medium for producing Navicula sp. galur NLA biomass (Tukey test, P<0.05), and this medium is used for the next experiments. To determine the type of nitrogen suitable for Navicula sp. galur NLA, the cells were grown in modified medium with different nitrogen sources (urea, nitrate, and ammonium with the same mole nitrogen). The results showed that the highest productivity of Navicula sp. galur NLA cells was in modified medium with a nitrogen nitrate source of 16.33±0.74 × 106 cell mL?1 (Turkey test, P<0.05, with a ratio of total carotenoid to Chl a of 1.94 observed on 7th d. In this growth medium, the amount of ?-carotene and fucoxanthin obtained was 19.69±0.38 µg g?1 and 5.52±0.25 mg g?1 dry cell, respectively. To obtain a large amount of ?-carotene and fucoxanthin, Navicula sp. galur NLA cells were grown in a modified medium with a concentration of nitrogen 14 and 140 mg L?1. The results showed that Navicula sp. galur NLA which was cultured in a modified medium with a nitrogen concentration of 14 mg L?1 in indoor produced ?-carotene (22.23±0.01 µg g?1 dry cell) which was significantly different from that from cells cultured with a nitrogen concentration of 140 mg L?1 (20.02±0.14 ?g g?1 dry cells) (Tukey test,P<0.05). However, fucoxanthin content (5.51±0.06 mg g?1 dry cell) produced by Navicula sp. galur NLA grown in a modified medium with a nitrogen concentration of 140 mg L?1 were 1.9 times higher than that with a nitrogen concentration of 14 mg L?1. These indicated that Navicula sp. galur NLA cells accumulated ?-carotene under low nitrogen nutrition, or accumulates fucoxanthin under high nitrogen nutrition. To accumulate ?-carotene and fucoxanthin, Navicula sp. galur NLA cells were cultivated in modified medium under limited silicate. In silicate concentration of 5.9 mg L ?1 (one tenth of its normal concentration), biomass productivity of Navicula sp. galur NLA decreased significantly. In this condition, Navicula sp. galur NLA produced ?-carotene (24.41±0.23 µg g?1 dry cell) 1.2 times higher than that normal condition, and fucoxanthin (4.07±0.02 mg g?1 dry cell) 1.3 times lower. When ?-carotene increased in low silicate, fucoxanthin decreased resulting in decreasing a ratio of fucoxanthin to ?-carotene. The growth of Navicula sp. galur NLA indoors at different light intensities (0, 13.5, 67.5, 135, and 202 µmol m?2s?1) was also observed. The results showed that the amount of ?-carotene and fucoxanthin (5.4±0.1 mg g?1 and 19.9 ±0.2 µg g?1 dry cell, respectively) produced by Navicula sp. galur NLA at light intensity of 202 µmol m?2s?1 were higher compared to that at other intensities. Navicula sp. galur NLA cultured under high light intensity increased of ?-carotene accumulation, while fucoxanthin/?-carotene ratio was reduced. So, Navicula sp. galur NLA cultured under high light intensity accumulated more ?-carotene. To understand the cell response to direct sun exposure (with a maximum intensity of 13 times higher that in indoor), Navicula sp. galur NLA cells were cultured in a modified medium in outdoor photobioreactors. The density of Navicula sp. galur NLA cells was 8.85±0.54 × 106 cells mL?1 (1.9 times lower than that in indoor), but the amount of ?-carotene (24.08±0.94 mg g?1 dry cell) was 1.2 times higher and fucoxanthin (2.61±0.03 mg g?1 dry cells) was 2.1 times lower. Meanwhile, when the cells were cultivated in a modified medium with a low nitrogen concentration (14 mg L?1), the amount of ?-carotene was 32.53±0.32 ?g g?1, so this medium was chosen for a large scale production of Navicula sp. galur NLA biomass. Under light stress conditions, Navicula sp. galur NLA cell size was reduced. Among Navicula sp. galur NLA carotenoids, the amount of ?-carotene and fucoxantin expressed by the cell in response to light stress was very dynamic. Fuco content of Navicula sp. galur NLA decreased from 5.40 ± 0.05 (indoor) to 2.61 ± 0.06 (outdoor) mg g–1 dried biomass. However, ?- carotene content of Navicula sp. galur NLA increased from 19.99 ± 0.16 (indoor) to 24.08 ± 0.16 (outdoor) ?g g–1of dried biomass, which indicated the importance of ?-carotene for cell photoprotection.