Novel biorefinery supply chains for wastewater valorization and production of high market value bio products using microalgae
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Introduction
For stable microalgae cultivations, several environmental factors have to be taken into consideration and be carefully designed. The supply of sunlight, CO2, water and nutrients such as phosphorus or nitrogen are only a few of the various parameters that need to be satisfied for the microalgae to grow and provide the desired products. Culture conditions such as pH or temperature are also critical to be maintained in desired levels.
Illumination
Sunlight is captured by microalgae in their chloroplast and is utilized for the conversion of carbon dioxide into glucose through the Calvin cycle process. Microalgae display better photon conversion effectiveness and overall photosynthetic efficiency than land plants. Microalgae are able to direct most of their energy into cell division (6 to 12-hour cycle) allowing for rapid biomass production. Also, unlike land plants, algae are lacking supportive structures such as stems and roots that are energetically expensive to produce. The source of light can be natural or artificial (typically through the employment of LED lamps). When in natural habitats, the light conditions (daily and seasonal changes in solstice altitude, light scattering by the atmosphere etc.) of the cultivation are set by the geography of the area are subject to significant variations and are beyond any control. In cases like this, specific microalgae strains that are native and capable to adapt in these specific conditions may be preferable to others. On the other hand, it is possible with artificial lighting to have a greater design input but this flexibility comes with increased operating costs and energy consumption.
The use of LEDs at night increased microalgae production CCMAR
Sunlight is captured by microalgae in their chloroplast and is utilized for the conversion of carbon dioxide into glucose through the Calvin cycle process. Microalgae display better photon conversion effectiveness and overall photosynthetic efficiency than land plants. Microalgae are able to direct most of their energy into cell division (6 to 12-hour cycle) allowing for rapid biomass production. Also, unlike land plants, algae are lacking supportive structures such as stems and roots that are energetically expensive to produce. The source of light can be natural or artificial (typically through the employment of LED lamps).
When in natural habitats, the light conditions (daily and seasonal changes in solstice altitude, light scattering by the atmosphere etc.) of the cultivation are set by the geography of the area are subject to significant variations and are beyond any control. In cases like this, specific microalgae strains that are native and capable to adapt in these specific conditions may be preferable to others. On the other hand, it is possible with artificial lighting to have a greater design input but this flexibility comes with increased operating costs and energy consumption.
Light intensity
The availability of light is crucial since the photosynthetic activity of the cells increases with light intensity. A lot of problems with microalgae cultivations can be traced to light intensity and availability. As the microalgae grow and multiply, the cell density increases resulting in shading of distant microalgae from the cells closer to the light source. Likewise, in cultivation systems that display high depths, the biomass in the bottom might not see as much light as the one in the surface. In cases like this, it might be necessary to increase the light intensity in order to penetrate through the culture. In a comprehensive review by Matlsev et al, the optimal values of the light intensity at which the maximum growth rate was observed for different taxonomic groups and species of algae were in the range of 26–400 μmol photons m−2 s−1.
Light duration
Also known as photoperiod, this is another critical parameter, particularly for autotrophic cultivations. A common strategy is to subject the cultivation to a long illumination period, even a constant 24-hour cycle. Various microalgae species however, have distinct preferences for light-dark patterns, and aligning the photoperiod with their natural rhythms could be crucial for maximizing biomass production. In this context, the use of appropriate light-dark (L:D) photoperiods has been reported to reduce the light energy demand with similar or even higher productivity. There are reports that shorter illumination periods (also known as flashing light effect) might lead to increased biomass production as well as reduced operation costs. The studies available in the literature provide unfortunately conflicting reports so optimization of the PBR structure in each application is necessary.
Illumination depth
Microalgae illumination at different wavelengths
Light wavelength
The wavelength of light also affects the metabolism and pigment composition of the cells. Microalgae use light of wavelengths from 400 to 700 nm for photosynthesis although this might differ depending on the species. For example, the green microalgae absorb light energy for photosynthesis through chlorophylls in the range of 450-475 nm as a major pigment absorbing light energy in the range of 450–475 nm and 630–675 nm and carotenoids as an accessory pigment absorbing light energy of 400–550 nm. As reported by Chen et al., although red light is optimal for algae growth, yellow light resulted in the highest production rate of chlorophylla, and blue light was optimal for the production of specific pigments (chlorophylla and phycocyanin) in Spirulina platensis.
Nutrients
Microalgae need a number of nutrients for their growth and survival. Like all land plants, they need a source of carbon and illumination for photosynthesis but other nutrients such as nitrogen are crucial for their development.
Carbon
Carbon is the main component of the microalgae, reaching up to 50% w/w. Microalgae are able to utilize carbon from different sources for their growth. The use of carbon dioxide, either from the atmosphere or industrial exhaust gases, can contribute significantly to the reduction of the production costs and at the same time the reduction of the emission of this greenhouse gas. The optimal carbon dioxide feed-stock can vary significantly not only between different microalgae strains but also for the same microalga when grown in different conditions. To a certain degree, increasing the CO2 concentration can accelerate photosynthesis with concentrations up to 10% is typically applied.
Other sources of carbon tested for microalgae cultivation include glucose, acetate and propionate. In this scenario, also known as heterotrophic cultivation, the microalgae are displaying significantly higher growth rates and biomass productivity. This is accompanied however, with an additional, usually expensive, raw material (for the heterotrophic cultivation of the aforementioned Auxenochlorella protothecoides, Li et al estimated that 80 % of the cost of culture medium belongs to the supplied glucose. But it is a very interesting option for commercial applications targeting high value products such as pigments.
Nitrogen
The second most abundant element in the microalga biomass, representing up to 10% of the cell. Nitrogen is an essential building block of nucleic acids and proteins and therefore a vital macronutrient for the microalgae development and reproduction. Nitrogen can be assimilated in the forms of nitrate, nitrite, urea and ammonium with nitrate being more preferable as it is more stable. The abundance of nitrogen has a direct effect in the evolution of the cultivation. A depletion of nitrogen, also known as ‘nitrogen starvation’, in the cultivation medium causes a decrease in growth with concomitant increases in the lipid productivities and fatty acid profile.
Phosphorus
The last most important compound for the microalgal growth, lipid production and other metabolic processes. Phosphorus is used as an energy currency in signaling and driving reactions and as a building block for nucleic acids and lipid membranes. A typical algal cell appears to be dominated by phosphate, phosphoester (monoester and diester) and polyphosphate. There are two main processes for phosphorus accumulation. One is the extracellular phosphorus adsorption during which the extracellular polymeric substances (mainly protein and carbohydrates) form complexes with phosphate which can be accounted for 16-46% of total P in microalgae. The other is the intracellular P uptake which is carried out by various phosphorus entrapping mechanisms, mainly the phosphate metabolism and the formation of polyphosphate.
Wastewater
Wastewater is an unfortunate byproduct of most urban and industrial activities. The purification of these water bodies is a necessary step before their release into the environment. This is typically achieved through costly and energy intensive chemical and biological processes. There is a drive however, in the tenets of circular economy, to valorize these wastewater streams or their treatment. One such way is through microalgae cultivation.
Nutrient and water supplies for microalgae cultivation are the major cost-contributory factors. The cultivation of microalgae at industrial scale would require a substantial amount of nutrients, mainly nitrogen and phosphorus. If chemical or organic fertilizers are used for the supply of these nutrients, it might lead to a 50% overall energy usage and GHG emissions according to some LCA analysis. A pathway to minimize cultivation costs would be to utilize wastewater as a culture medium for the microalgae. Wastewaters are typically rich in these two elements which must be removed prior their discharge to avoid eutrophication of nearby water bodies. Microalgae cultivation in wastewater thus provides a very interesting solution for these two problems. Moreover, it would help wastewater treatment plants to reduce their energy consumption by 60-80% which typically is spent in the removal of nitrate and phosphate. A final advantage would be the reduction of the amounts of water required for the cultivation, especially in areas which are already facing water sparsity. Cultivation of microalgae in wastewaters such as brewery wastewaters, cheese-whey, piggery wastewater is well documented and research on this topic is still very intense highlighting the potential microalgae role in a circular bioeconomy.
Bibliography
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Radin Maya Saphira Radin Mohamed Maizatul Azrina Yaakob, Adel Al-Gheethi; Ambati, Ranga Rao
Influence of Nitrogen and Phosphorus on Microalgal Growth, Biomass, Lipid, and Fatty Acid Production: An Overview Journal Article
In: Cells, vol. 10, iss. 2, pp. 393, 2021.
@article{nokey,
title = {Influence of Nitrogen and Phosphorus on Microalgal Growth, Biomass, Lipid, and Fatty Acid Production: An Overview},
author = {Maizatul Azrina Yaakob, Radin Maya Saphira Radin Mohamed, Adel Al-Gheethi, Ravishankar Aswathnarayana Gokare and Ranga Rao Ambati},
url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7918059/},
doi = {10.3390/cells10020393},
year = {2021},
date = {2021-02-14},
urldate = {2021-02-14},
journal = {Cells},
volume = {10},
issue = {2},
pages = {393},
abstract = {Microalgae can be used as a source of alternative food, animal feed, biofuel, fertilizer, cosmetics, nutraceuticals and for pharmaceutical purposes. The extraction of organic constituents from microalgae cultivated in the different nutrient compositions is influenced by microalgal growth rates, biomass yield and nutritional content in terms of lipid and fatty acid production. In this context, nutrient composition plays an important role in microalgae cultivation, and depletion and excessive sources of this nutrient might affect the quality of biomass. Investigation on the role of nitrogen and phosphorus, which are crucial for the growth of algae, has been addressed. However, there are challenges for enhancing nutrient utilization efficiently for large scale microalgae cultivation. Hence, this study aims to highlight the level of nitrogen and phosphorus required for microalgae cultivation and focuses on the benefits of nitrogen and phosphorus for increasing biomass productivity of microalgae for improved lipid and fatty acid quantities. Furthermore, the suitable extraction methods that can be used to utilize lipid and fatty acids from microalgae for biofuel have also been reviewed.},
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Maltsev, Yevhen; Maltseva, Kateryna; Kulikovskiy, Maxim; Maltseva, Svetlana
Influence of Light Conditions on Microalgae Growth and Content of Lipids, Carotenoids, and Fatty Acid Composition Journal Article
In: Biology, vol. 10, no. 10, 2021, ISSN: 2079-7737.
@article{biology10101060,
title = {Influence of Light Conditions on Microalgae Growth and Content of Lipids, Carotenoids, and Fatty Acid Composition},
author = {Yevhen Maltsev and Kateryna Maltseva and Maxim Kulikovskiy and Svetlana Maltseva},
url = {https://www.mdpi.com/2079-7737/10/10/1060},
doi = {10.3390/biology10101060},
issn = {2079-7737},
year = {2021},
date = {2021-01-01},
urldate = {2021-01-01},
journal = {Biology},
volume = {10},
number = {10},
abstract = {Microalgae are a valuable natural resource for a variety of value-added products. The growth of microalgae is determined by the impact of many factors, but, from the point of view of the implementation of autotrophic growth, light is of primary importance. This work presents an overview of the influence of light conditions on the growth of microalgae, the content of lipids, carotenoids, and the composition of fatty acids in their biomass, taking into account parameters such as the intensity, duration of lighting, and use of rays of different spectral composition. The optimal light intensity for the growth of microalgae lies in the following range: 26−400 µmol photons m−2 s−1. An increase in light intensity leads to an activation of lipid synthesis. For maximum lipid productivity, various microalgae species and strains need lighting of different intensities: from 60 to 700 µmol photons m−2 s−1. Strong light preferentially increases the triacylglyceride content. The intensity of lighting has a regulating effect on the synthesis of fatty acids, carotenoids, including β-carotene, lutein and astaxanthin. In intense lighting conditions, saturated fatty acids usually accumulate, as well as monounsaturated ones, and the number of polyunsaturated fatty acids decreases. Red as well as blue LED lighting improves the biomass productivity of microalgae of various taxonomic groups. Changing the duration of the photoperiod, the use of pulsed light can stimulate microalgae growth, the production of lipids, and carotenoids. The simultaneous use of light and other stresses contributes to a stronger effect on the productivity of algae.},
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Gabriela F. Ferreira Sérgio S. de Jesus, Larissa S. Moreira
Comparison of several methods for effective lipid extraction from wet microalgae using green solvents Journal Article
In: Renewable Energy, vol. 143, pp. 130-141, 2019, ISSN: 0960-1481.
@article{nokey,
title = {Comparison of several methods for effective lipid extraction from wet microalgae using green solvents},
author = {Sérgio S. de Jesus, Gabriela F. Ferreira, Larissa S. Moreira, Maria Regina Wolf Maciel, Rubens Maciel Filho,},
doi = {https://doi.org/10.1016/j.renene.2019.04.168},
issn = {0960-1481},
year = {2019},
date = {2019-12-01},
urldate = {2019-12-01},
journal = {Renewable Energy},
volume = {143},
pages = {130-141},
abstract = {A comparative study of lipid extraction from microalgae was performed using the Soxhlet, Bligh and Dyer, Folch, and Hara and Radin methods, with the green solvents 2-methyltetrahydrofuran (2-MeTHF) and cyclopentyl methyl ether (CPME), which have also been used in previously published studies. Extractions were performed with the microalgae Chlorella pyrenoidosa at 65.71% moisture. The Bligh and Dyer methodology, using the solvents 2-MeTHF:isoamyl alcohol (2:1 v/v) and CPME:methanol (1:1.7 v/v), extracted 95.73 ± 0.52 and 89.35 ± 7.98 mg lipids/g biomass, respectively. Regarding fatty acids yield, CPME showed higher selectivity than 2-MeTHF. A brief cost-effectiveness and energy analysis of the extraction process was performed. Based on the calculations, this study concluded that the energy required for the evaporation of the solvent and mixture of solvents after the extraction process has no significant economic impact; the largest expense is associated with solvent consumption. To extract 1 kg of fatty acids, the Hara and Radin method using hexane:isopropanol (3:2 v/v) proved to be the most cost-effective. Results show that these solvents prices’ are still not competitive when compared to fossil-based solvents. The price reduction of 2-MeTHF would make it more attractive than CPME, as it requires a lower amount of biomass.},
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}
In Yung Sunwoo So Hee Kim, Hee Jun Hong
In: Bioprocess and Biosystems Engineering, vol. 42, pp. 1517–1526, 2019.
@article{nokey,
title = {Lipid and unsaturated fatty acid productions from three microalgae using nitrate and light-emitting diodes with complementary LED wavelength in a two-phase culture system},
author = {So Hee Kim, In Yung Sunwoo, Hee Jun Hong, Che Clovis Awah, Gwi-Taek Jeong & Sung-Koo Kim},
url = {https://link.springer.com/article/10.1007/s00449-019-02149-y#article-info},
doi = {https://doi.org/10.1007/s00449-019-02149-y},
year = {2019},
date = {2019-05-20},
journal = {Bioprocess and Biosystems Engineering},
volume = {42},
pages = {1517–1526},
abstract = {In this study, Pavlova lutheri, Chlorella vulgaris, and Porphyridium cruentum were cultured using modified F/2 media in a 1 L flask culture. Various nitrate concentrations were tested to determine an optimal nitrate concentration for algal growth. Subsequently, the effect of light emitted at a specific wavelength on biomass and lipid production by three microalgae was evaluated using various wavelengths of light-emitting diodes (LED). Biomass production by P. lutheri, C. vulgaris, and P. cruentum were the highest with blue, red, and green LED wavelength with 1.09 g dcw/L, 1.23 g dcw/L, and 1.28 g dcw/L on day 14, respectively. Biomass production was highest at the complementary LED wavelength to the color of microalgae. Lipid production by P. lutheri, C. vulgaris, and P. cruentum were the highest with yellow, green, and red LEDs’ wavelength, respectively. Eicosapentaenoic acid production by P. lutheri, C. vulgaris, and P. cruentum was 10.35%, 10.14%, and 14.61%, and those of docosahexaenoic acid were 6.09%, 8.95%, and 11.29%, respectively.},
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Demory, David; Combe, Charlotte; Hartmann, Philipp; Talec, Amélie; Pruvost, Eric; Hamouda, Raouf; Souillé, Fabien; Lamare, Pierre-Olivier; Bristeau, Marie-Odile; Sainte-Marie, Jacques; Rabouille, Sophie; Mairet, Francis; Sciandra, Antoine; Bernard, Olivier
How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments Journal Article
In: Royal Society Open Science, vol. 5, no. 180523, 2018, ISSN: 2054-5703.
@article{Demory2018,
title = {How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments},
author = {David Demory and Charlotte Combe and Philipp Hartmann and Amélie Talec and Eric Pruvost and Raouf Hamouda and Fabien Souillé and Pierre-Olivier Lamare and Marie-Odile Bristeau and Jacques Sainte-Marie and Sophie Rabouille and Francis Mairet and Antoine Sciandra and Olivier Bernard},
doi = {10.1098/rsos.180523},
issn = {2054-5703},
year = {2018},
date = {2018-05-30},
urldate = {2018-05-00},
journal = {Royal Society Open Science},
volume = {5},
number = {180523},
publisher = {The Royal Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Charlotte Combe David Demory, Philipp Hartmann; Bernard, Olivier
How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments Journal Article
In: Royal Society, vol. 5, iss. 5, 2018, ISSN: 2054-5703.
@article{nokey,
title = {How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments},
author = {David Demory, Charlotte Combe, Philipp Hartmann, Amélie Talec, Eric Pruvost, Raouf Hamouda, Fabien Souillé, Pierre-Olivier Lamare, Marie-Odile Bristeau, Jacques Sainte-Marie, Sophie Rabouille, Francis Mairet, Antoine Sciandra and Olivier Bernard},
url = {https://royalsocietypublishing.org/doi/10.1098/rsos.180523},
doi = {https://doi.org/10.1098/rsos.180523},
issn = {2054-5703},
year = {2018},
date = {2018-05-30},
journal = {Royal Society},
volume = {5},
issue = {5},
abstract = {Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are non-trivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier–Stokes equations tailored to systems with free surfaces. The trajectory of a particular cell was selected and the associated high-frequency light pattern was computed. This light pattern was then experimentally reproduced in an Arduino-driven computer controlled cultivation system with a low density Dunaliella salina culture. The effect on growth and pigment content was recorded for various frequencies of the light pattern, by setting different paddle wheel velocities. Results show that the frequency of this realistic signal plays a decisive role in the dynamics of photosynthesis, thus revealing an unexpected photosynthetic response compared to that recorded under the on/off signals usually used in the literature. Indeed, the light received by a single cell contains signals from low to high frequencies that nonlinearly interact with the photosynthesis process and differentially stimulate the various time scales associated with photoacclimation and energy dissipation. This study highlights the need for experiments with more realistic light stimuli to better understand microalgal growth at high cell densities. An experimental protocol is also proposed, with simple, yet more realistic, step functions for light fluctuations.
},
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Xu, Yanan; Ibrahim, Iskander M.; Wosu, Chiziezi I.; Ben-Amotz, Ami; Harvey, Patricia J.
Potential of New Isolates of Dunaliella Salina for Natural β-Carotene Production Journal Article
In: Biology, vol. 7, no. 1, 2018, ISSN: 2079-7737.
@article{biology7010014,
title = {Potential of New Isolates of Dunaliella Salina for Natural β-Carotene Production},
author = {Yanan Xu and Iskander M. Ibrahim and Chiziezi I. Wosu and Ami Ben-Amotz and Patricia J. Harvey},
url = {https://www.mdpi.com/2079-7737/7/1/14},
doi = {10.3390/biology7010014},
issn = {2079-7737},
year = {2018},
date = {2018-01-01},
urldate = {2018-01-01},
journal = {Biology},
volume = {7},
number = {1},
abstract = {The halotolerant microalga Dunaliella salina has been widely studied for natural β-carotene production. This work shows biochemical characterization of three newly isolated Dunaliella salina strains, DF15, DF17, and DF40, compared with D. salina CCAP 19/30 and D. salina UTEX 2538 (also known as D. bardawil). Although all three new strains have been genetically characterized as Dunaliella salina strains, their ability to accumulate carotenoids and their capacity for photoprotection against high light stress are different. DF15 and UTEX 2538 reveal great potential for producing a large amount of β-carotene and maintained a high rate of photosynthesis under light of high intensity; however, DF17, DF40, and CCAP 19/30 showed increasing photoinhibition with increasing light intensity, and reduced contents of carotenoids, in particular β-carotene, suggesting that the capacity of photoprotection is dependent on the cellular content of carotenoids, in particular β-carotene. Strong positive correlations were found between the cellular content of all-trans β-carotene, 9-cis β-carotene, all-trans α-carotene and zeaxanthin but not lutein in the D. salina strains. Lutein was strongly correlated with respiration in photosynthetic cells and strongly related to photosynthesis, chlorophyll and respiration, suggesting an important and not hitherto identified role for lutein in coordinated control of the cellular functions of photosynthesis and respiration in response to changes in light conditions, which is broadly conserved in Dunaliella strains. Statistical analysis based on biochemical data revealed a different grouping strategy from the genetic classification of the strains. The significance of these data for strain selection for commercial carotenoid production is discussed.},
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Bleakley, Stephen; Hayes, Maria
Algal Proteins: Extraction, Application, and Challenges Concerning Production Journal Article
In: Foods, vol. 6, iss. 5, pp. 33, 2017.
@article{nokey,
title = {Algal Proteins: Extraction, Application, and Challenges Concerning Production},
author = {Stephen Bleakley and Maria Hayes},
editor = {Population growth combined with increasingly limited resources of arable land and fresh water has resulted in a need for alternative protein sources. Macroalgae (seaweed) and microalgae are examples of under-exploited “crops”. Algae do not compete with traditional food crops for space and resources. This review details the characteristics of commonly consumed algae, as well as their potential for use as a protein source based on their protein quality, amino acid composition, and digestibility. Protein extraction methods applied to algae to date, including enzymatic hydrolysis, physical processes, and chemical extraction and novel methods such as ultrasound-assisted extraction, pulsed electric field, and microwave-assisted extraction are discussed. Moreover, existing protein enrichment methods used in the dairy industry and the potential of these methods to generate high value ingredients from algae, such as bioactive peptides and functional ingredients are discussed. Applications of algae in human nutrition, animal feed, and aquaculture are examined.},
doi = {10.3390/foods6050033},
year = {2017},
date = {2017-04-26},
urldate = {2017-04-26},
journal = {Foods},
volume = {6},
issue = {5},
pages = {33},
abstract = {Population growth combined with increasingly limited resources of arable land and fresh water has resulted in a need for alternative protein sources. Macroalgae (seaweed) and microalgae are examples of under-exploited “crops”. Algae do not compete with traditional food crops for space and resources. This review details the characteristics of commonly consumed algae, as well as their potential for use as a protein source based on their protein quality, amino acid composition, and digestibility. Protein extraction methods applied to algae to date, including enzymatic hydrolysis, physical processes, and chemical extraction and novel methods such as ultrasound-assisted extraction, pulsed electric field, and microwave-assisted extraction are discussed. Moreover, existing protein enrichment methods used in the dairy industry and the potential of these methods to generate high value ingredients from algae, such as bioactive peptides and functional ingredients are discussed. Applications of algae in human nutrition, animal feed, and aquaculture are examined.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
imagePolur Hanumantha Rao Ramanathan Ranjith Kumar, imageMuthu Arumugam
Lipid extraction methods from microalgae: a comprehensive review Journal Article
In: Frontiers in Energy Research, vol. 2, 2015.
@article{nokey,
title = {Lipid extraction methods from microalgae: a comprehensive review},
author = {Ramanathan Ranjith Kumar, imagePolur Hanumantha Rao, imageMuthu Arumugam},
url = {https://www.frontiersin.org/articles/10.3389/fenrg.2014.00061/full},
doi = { https://doi.org/10.3389/fenrg.2014.00061},
year = {2015},
date = {2015-01-08},
urldate = {2015-01-08},
journal = {Frontiers in Energy Research},
volume = {2},
abstract = {Energy security has become a serious global issue and a lot of research is being carried out to look for economically viable and environment-friendly alternatives. The only solution that appears to meet futuristic needs is the use of renewable energy. Although various forms of renewable energy are being currently used, the prospects of producing carbon-neutral biofuels from microalgae appear bright because of their unique features such as suitability of growing in open ponds required for production of a commodity product, high CO2-sequestering capability, and ability to grow in wastewater/seawater/brackish water and high-lipid productivity. The major process constraint in microalgal biofuel technology is the cost-effective and efficient extraction of lipids. The objective of this article is to provide a comprehensive review on various methods of lipid extraction from microalgae available, to date, as well as to discuss their advantages and disadvantages. The article covers all areas of lipid extraction procedures including solvent extraction procedures, mechanical approaches, and solvent-free procedures apart from some of the latest extraction technologies. Further research is required in this area for successful implementation of this technology at the production scale.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Suh, William I.; Mishra, Sanjiv K.; Kim, Tae-Hyoung; Farooq, Wasif; Moon, Myounghoon; Shrivastav, Anupama; Park, Min S.; Yang, Ji-Won
Direct transesterification of wet microalgal biomass for preparation of biodiesel Journal Article
In: Algal Research, vol. 12, pp. 405-411, 2015, ISSN: 2211-9264.
@article{SUH2015405,
title = {Direct transesterification of wet microalgal biomass for preparation of biodiesel},
author = {William I. Suh and Sanjiv K. Mishra and Tae-Hyoung Kim and Wasif Farooq and Myounghoon Moon and Anupama Shrivastav and Min S. Park and Ji-Won Yang},
url = {https://www.sciencedirect.com/science/article/pii/S2211926415300801},
doi = {https://doi.org/10.1016/j.algal.2015.10.006},
issn = {2211-9264},
year = {2015},
date = {2015-01-01},
urldate = {2015-01-01},
journal = {Algal Research},
volume = {12},
pages = {405-411},
abstract = {Most conventional processes for algal biodiesel production involve separate lipid extraction steps or require usage of dry biomass that incurs extra cost and an energy intensive drying step. A novel process that involves dehydration of wet biomass via pretreatment with ethanol followed by direct in situ transesterification into biodiesel was investigated in this study. Under mild esterification at 80°C for 30min, pretreating the wet biomass twice with 3 volumes of ethanol resulted in a nearly four-fold increase of fatty acid ethyl ester (FAEE) yield from 3.04mg to 11.78mg, while increasing the ethanol from 1 volume to 10 volumes resulted in a six fold increase of yield from 3.18 to 18.29mg. The FAEE yield further increased when the esterification reaction was run at higher temperature and longer durations of up to 120°C for 2h. The overall positive impact of the pretreatment step on the final yield was far greater for milder reaction conditions, which makes the process more attractive in terms of economics and energy savings. In addition, it was found that the yield is unaffected by the choice of alcohol, which means methanol and butanol can also be used for the process. Lastly, it was found that the low concentration of water in the FAEE containing spent ethanol meant that both the solvent and sulfuric acid could be reused to further concentrate the quantity of FAEE in the final product mixture.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Sayre, Richard
Microalgae: The Potential for Carbon Capture Journal Article
In: BioScience, vol. 60, no. 9, pp. 722-727, 2010, ISSN: 0006-3568.
@article{10.1525/bio.2010.60.9.9,
title = {Microalgae: The Potential for Carbon Capture},
author = {Richard Sayre},
url = {https://doi.org/10.1525/bio.2010.60.9.9},
doi = {10.1525/bio.2010.60.9.9},
issn = {0006-3568},
year = {2010},
date = {2010-01-01},
urldate = {2010-01-01},
journal = {BioScience},
volume = {60},
number = {9},
pages = {722-727},
abstract = {There is growing recognition that microalgae are among the most productive biological systems for generating biomass and capturing carbon. Further efficiencies are gained by harvesting 100% of the biomass, much more than is possible in terrestrial biomass production systems. Micro-algae's ability to transport bicarbonate into cells makes them well suited to capture carbon. Carbon dioxide—or bicarbonate-capturing efficiencies as high as 90% have been reported in open ponds. The scale of microalgal production facilities necessary to capture carbon-dioxide (CO2) emissions from stationary point sources such as power stations and cement kilns is also manageable; thus, microalgae can potentially be exploited for CO2 capture and sequestration. In this article, I discuss possible strategies using microalgae to sequester CO2 with reduced environmental consequences.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Jacob-Lopes, Eduardo; Scoparo, Carlos Henrique Gimenes; Lacerda, Lucy Mara Cacia Ferreira; Franco, Telma Teixeira
Effect of light cycles (night/day) on CO2 fixation and biomass production by microalgae in photobioreactors Journal Article
In: Chemical Engineering and Processing: Process Intensification, vol. 48, no. 1, pp. 306-310, 2009, ISSN: 0255-2701.
@article{JACOBLOPES2009306,
title = {Effect of light cycles (night/day) on CO2 fixation and biomass production by microalgae in photobioreactors},
author = {Eduardo Jacob-Lopes and Carlos Henrique Gimenes Scoparo and Lucy Mara Cacia Ferreira Lacerda and Telma Teixeira Franco},
url = {https://www.sciencedirect.com/science/article/pii/S0255270108001037},
doi = {https://doi.org/10.1016/j.cep.2008.04.007},
issn = {0255-2701},
year = {2009},
date = {2009-01-01},
urldate = {2009-01-01},
journal = {Chemical Engineering and Processing: Process Intensification},
volume = {48},
number = {1},
pages = {306-310},
abstract = {The objective of this study was to evaluate the effect of the photoperiod on the biomass production and carbon dioxide fixation rates using a photosynthetic culture of the cyanobacterium Aphanothece microscopica Nägeli in bubble column photobioreactors. The cultures were carried out at temperatures of 35°C, air enriched with carbon dioxide at concentrations of 15% and photon flux density of 150μmolm−2s−1. The light cycles evaluated were 0:24, 2:22, 4:20, 6:18, 8:16, 10:14, 12:12, 14:10, 16:8, 18:6, 20:4, 22:2 and 24:0 (night:day), respectively. The results obtained indicated that the duration of the light periods was a determinant factor in the performance of the photobioreactors. A linear reduction in biomass production and carbon dioxide fixation with reductions in the duration of the light period was evident, with the exception of the 12:12 (night:day) cycles. Reductions of up to 99.69% in the carbon-fixation rates as compared with cultures under continuous illumination were obtained.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
K. A. Gilles Michel DuBois, J. K. Hamilton; Smith, Fred.
Colorimetric Method for Determination of Sugars and Related Substances Journal Article
In: Analytical Chemistry, vol. 28, iss. 3, pp. 350-356, 1956.
@article{nokey,
title = {Colorimetric Method for Determination of Sugars and Related Substances},
author = {Michel DuBois, K. A. Gilles, J. K. Hamilton, P. A. Rebers, and Fred. Smith},
doi = {https://doi.org/10.1021/ac60111a017},
year = {1956},
date = {1956-03-01},
urldate = {1956-03-01},
journal = {Analytical Chemistry},
volume = {28},
issue = {3},
pages = {350-356},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
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The project “Novel biorefinery supply chains for wastewater valorization and production of high market value bio products using microalgae (BlueBioChain)” Project ID 31, is part of the BlueBio ERA-NET Cofund under the European Union’s Horizon 2020 Research and Innovation programme (Grant agreement No. 817992) (Project ID 31 BlueBioChain).
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