Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae (original) (raw)
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Gravity : Jurnal Ilmiah Penelitian dan Pembelajaran Fisika
A closed photobioreactor design has been fabricated, aimed to determine the basic concept for microalgae Chlorella vulgaris development. This study employed a flat-plate type with dimensions of 16x20x25 cm with the effectiveness of 3000 ml culture media and two 20 watt 220 volt tungsten halogen lamps, which were placed on the right and left sides of the reactor with a light intensity of 1000 lux. This study employed two photobioreactors, type-I without CO 2 supply and type-II with CO 2 supply as much as 25%. The initial cell density of Chlorella vulgaris culture was 14,694 x10 5 cells/ml; then observations were made every day using a Haemocytometer. O 2 concentration data were collected every day 3 times with irradiation time of 1, 6, and 9 hours using the O 2 gas sensor (KE-50 type). The determination of the O 2 concentration value in the photobioreactor on the 3 rd day was 0.69%.
Microalgae are among the most promising organisms for biofuel production. However, microalgae-based biofuels are not economically feasible and many efforts are in progress worldwide to achieve this goal. Here we report the effects of cultivation with input of pure CO 2 on the growth, nutrient uptake, and chemical composition of two marine microalgae: Chlorella sp. and Nannochloropsis oculata. Chlorella sp. grew more with addition of CO 2 , but no difference was detected in the experiments performed with N. oculata. Both species showed an efficient consumption of dissolved nitrate and phosphate, and the nutrient uptake tended to be faster in the experiments with input of carbon dioxide. Carbohydrates were the most abundant substances in both species, and their concentrations increased dramatically in Chlorella sp. in the experiment with CO 2 . Protein and lipid contents were relatively low in both microalgae, and these substances did not increase with the addition of CO 2 . Results s...
Physiologia Plantarum, 2008
Unicellular green alga Chlorella minutissima, grown under extreme carbon dioxide concentrations (0.036-100%), natural temperature and light intensities (Mediterranean conditions), strongly increase the microalgal biomass through photochemical and non-photochemical changes in the photosynthetic apparatus. Especially, CO 2 concentrations up to 10% enhance the density of active reaction centers (RC/CS o), decrease the antenna size per active reaction center (ABS/RC), decrease the dissipation energy (DI o /RC) and enhance the quantum yield of primary photochemistry (F v /F m). Higher CO 2 concentrations (20-25%) combine the above-mentioned photochemical changes with enhanced non-photochemical quenching of surplus energy, which leads to an enhanced steady-state fraction of 'open' (oxidized) PSII reaction centers (q p), and minimize the excitation pressure of PSII (1 2 q p) under very high light intensities (approximately 1700 mmol m 22 s 21 maximal value), avoiding the photoinhibition and leading to an enormous biomass production (approximately 2500%). In conclusion, these extreme CO 2 concentrations-about 1000 times higher than the ambient one-can be easily metabolized from the unicellular green alga to biomass and can be used, on a local scale at least, for the future development of microalgal photobioreactors for the mitigation of the factory-produced carbon dioxide.
The Science of the total environment, 2017
The extensive microalgae diversity offers considerable versatility for a wide range of biotechnological applications in environmental and production processes. Microalgal cultivation is based on CO2 fixation via photosynthesis and, consequently, it is necessary to evaluate, in a short time and reliable way, the effect of the CO2 gas concentration on the consumption rate and establish the tolerance range of different strains and the amount of inorganic carbon that can be incorporated into biomass in order to establish the potential for industrial scale application. Dynamic experiments allow calculating the short-term microalgal photosynthetic activity of strains in photobioreactors. In this paper, the effect of step-changes in CO2 concentration fed to a 20L bubble column photobioreactor on the CO2 consumption rate of Scenedesmus obtusiusculus was evaluated at different operation times. The highest apparent CO2 consumption rate (336μmolm(-2)s(-1) and 5.6% of CO2) was 6530mgCO2gb(-1)d(...
Technical insight on the requirements for CO2-saturated growth of microalgae in photobioreactors
3 Biotech, 2017
Microalgal cultures are usually sparged with CO2-enriched air to preclude CO2 limitation during photoautotrophic growth. However, the CO2 vol% specifically required at operating conditions to meet the carbon requirement of algal cells in photobioreactor is never determined and 1–10% v/v CO2-enriched air is arbitrarily used. A scheme is proposed and experimentally validated for Chlorella vulgaris that allows computing CO2-saturated growth feasible at given CO2 vol% and volumetric O2 mass-transfer coefficient (k L a)O. CO2 sufficiency in an experiment can be theoretically established to adjust conditions for CO2-saturated growth. The methodology completely eliminates the requirement of CO2 electrode for online estimation of dissolved CO2 to determine critical CO2 concentration (Ccrit), specific CO2 uptake rate (SCUR), and volumetric CO2 mass-transfer coefficient (k L a)C required for the governing CO2 mass-transfer equation. Ccrit was estimated from specific O2 production rate (SOPR) ...
Sugar-stimulated CO2 sequestration by the green microalga Chlorella vulgaris
Science of The Total Environment, 2018
To convert waste CO2 from flue gases of power plants into value-added products, biomitigation technologies show promise. In this study, we cultivated a fast-growing species of green microalgae, Chlorella vulgaris, in different sizes of photobioreactors (PBRs) and developed a strategy using small doses of sugars for enhancing CO2 sequestration under light-emitting diode illumination. Glucose supplementation at low levels resulted in an increase of photoautotrophic growth-driven biomass generation as well as CO2 capture by 10% and its enhancement corresponded to an increase of supplied photon flux. The utilization of urea instead of nitrate as the sole nitrogen source increased photoautotrophic growth by 14%, but change of nitrogen source didn't compromise glucose-induced enhancement of photoautotrophic growth. The optimized biomass productivity achieved was 30.4% higher than the initial productivity of purely photoautotrophic culture. The major pigments in the obtained algal biomass were found comparable to its photoautotrophic counterpart and a high neutral lipids productivity of 516.6 mg/(L•day) was achieved after optimization. A technoeconomic model was also developed, indicating that LED-based PBRs represent a feasible strategy for converting CO2 into value-added algal biomass.
Microalgae have the potential to recycle and bioremediate CO 2 and also produce chemical energy in the form of biomass. The potential production of renewable energy and high value products (i.e. carotenoid, antioxidants and polyunsaturated fatty acids) makes large scale microalgal cultivation an attractive application. To achieve high productivity all microalgae cultures require CO 2 addition. Various microalgae species have shown different capabilities to bioremediate CO 2 . This review article reports biomass concentrations, biomass productivities, and CO 2 fixation rates of several microalgae and cyanobacteria species under different input CO 2 concentrations. The effects of important factors such as type of photobioreactor, temperature, and light intensity on CO 2 removal are also discussed.
Journal of Process Control, 2011
Oleaginous microalgae are seen as a potential major biofuel producer in the future since, under conditions of nitrogen deprivation, they can contain high amounts of lipids, while they consume CO 2 from power plants. These photosynthetic microorganisms are however rather different from the microorganisms usually used in biotechnology. In particular, predicting the behaviour of microalgal based processes is delicate because of the strong interaction between biology (microalgal development and respiration), and physics (light attenuation and hydrodynamics). This paper reviews existing models, and in particular Droop Model which has been widely used to predict microalgal behaviour under nutrient limitation. It details a model for photobioreactors or raceways, when both light and nutrients are limiting. The challenges and hurdles to improve photobioreactor modelling and control in order to optimise biomass or biofuel production are then discussed.