Eukaryota, Chlorophyta, Trebouxiophyceae, Chlorellales, Chlorellaceae, Chlorella
Description and Significance
"Chlorella vulgaris" is a eukaryotic, unicellular green algae. "C. vulgaris" is estimated to have been on Earth for more than 2.5 billion years. During that time, it has needed to evolve for survival, resulting in many of the useful functions we use today and in the future(Liebke). Most of the important features deals with its ability to rapidly grow. Common practice normally involves growing populations in photobioreactors(Sacasa 2013). These chambers are consistently shaken and used to control certain aspects of metabolism in "C. vulgaris". Variables such as media, carbonation, and light have been researched heavily to understand the best means of optimal growth. Yuvraj et al. (2016) demonstrated that photoautotrophic growth of C. vulgaris is generally limited by depletion of nutrients (especially nitrogen), light attenuation, change in pH, carbon limitation, and accumulation of photosynthetic oxygen. Several uses of "C. vulgaris" have been researched. First, due to its high mineral and protein levels, it is used in vitamins and has even thought to be a viable food when dehydrated(Belasco 1997). It has powerful effects in boosting human health(Liebke). Secondly, many algae produce lipids through photosynthesis. This makes these organisms a viable source for biofuel. "C. vulgaris" is lipid content per biomass is approximately 42%. This is more than soybeans, sugarcane, and corn; making it a viable alternative for biodiesel(Yujie 2011). With current technology, it can match oil prices of $63.97 per barrel. This is not even mentioning the potential to make money back through waste water treatment(Yujie 2011). Waste water is treated even in textile production. Research shows that "C. vulgaris" reduced the color dye by 41.8%, Ammonium by 44%, Phosphate by 33%, and Carbon dioxide by 33-62%(Lim 2010). "C. vulgaris" ability has also been considered for reducing emissions from power plant. This mostly deals with the ability for rapid growth and the variety of uses. Despite the range of benefits, a negative aspect is the cost to grow "C. vulgaris". Vast areas would need to be used to make much of an impact. CO2 is a limiting resource for large quantities of C. vulgaris to grow rapidly, in exception to a coal burning power plant. Photobioreactors are often carbonated with brings an extremely high cost in energy to the equation.
C. vulgaris is a small, spherical algae that has a size of 5-10µm. It contains 16 chromosones consisting of a range between 0.98 Mb to 4 Mb("Chlorella vulgaris" C-169). This range is rather large due to different geographic location and being a free-living algae. Full sequencing of the chloroplast was found to contain 150,613 bp. The total genome does not have large sections that repeat. This missing inverted repeat is found in most alga. A genomic section found in "Escherichia coli" that are responsible for cell division was found in "C. vulgaris", indicating that chloroplast division in "C. vulgaris" resembles the division taking place in bacteria. Red and brown algae contribute no homologous genomic sections in its chloroplast which means that "C. vulgaris" is surprising more similar to land vegetation(Wakasugi 1997). When looking at life history, plants are thought to be evolved from green algae. This correlates with gene segments in "C. vulgaris" that exist in many plants that have been sequenced to date. Currently, no Mitochondrial sequencing has been performed.
Cell Structure, Metabolism and Life Cycle
Structure of the cell wall is unique for "C. vulgaris" compared to most related green algae. It possess and enzyme-digestible cell wall which is unlike other green algae. C. vulgaris is somewhat versatile with fixing carbon. "C. vulgaris" is a photolithoautotroph. Depending on the environment (media) it exists in, changes the byproducts resulting from metabolic processes. C. vulgaris is similar to most phototrophs because light is absorbed via the chloroplast. Green algae then fixes the CO2 into fatty acids within the cell. C. vulgaris fatty acid biomass changes with different amounts of carbohydrates present in the media. The presence of carbohydrate causes the formation of intercellular fatty acids to have long chains. In situations with little or no carbohydrates, this green algae forms linolenic acid. Similar to most green and red algae, C. vulgaris doesn’t not make unsaturated fatty acids(harris). This is important for the high lipid amounts found in green algae biomass. Also rather important, when C. vulgaris is grown on inorganic media, it contains more linolenic acid. This relates to the vast research about using Chlorella as a food source. Some green algae can be high in protein and is believed to be a healthy substance for human consumption(Warren 1997). Once the appropriate fatty acids are formed oxygen is then respirated and the CO2 is stored.
Ecology and Pathogenesis
Similar to most green algae, C. vulgaris is a freshwater micro-algae. All Chlorella species combine attribute to the largest source of chlorophyll(Liebke). During its many years on earth, it has developed important functions that we value in regards to human health. C. vulgaris is known to survive under certain stressors such as viruses, bacteria, fungi, and many types of pollutants. The reason for these attributes stems from its ability to rapidly repair its DNA(JGI). When a break occurs, C. vulgaris is able to mutate and assimilate rapidly. Because of this, researchers are trying to further understand this process to maybe benefit human health. Furthermore, when consumed it acts similar to an antibiotic. Chlorellan(substance produced by Chlorella) also can have properties of antitumor, antiviral, and even antifungal benefits(Liebke). Patients in need of detoxification can sometimes be treated with Chlorella(mix of species),making it a valuable tool for healthcare.
Sacasa Castellanos, Claudia, "Batch and Continuous Studies of Chlorella Vulgaris in Photo-Bioreactors" (2013). University of Western Ontario - Electronic Thesis and Dissertation Repository. Paper 1113. http://ir.lib.uwo.ca/etd/1113
Belasco, Warren (July 1997). "Algae Burgers for a Hungry World? The Rise and Fall of Chlorella Cuisine". Technology and Culture 38 (3): 608–34.doi:10.2307/3106856.JSTOR 3106856.
Feng, Y., Li, C., & Zhang, D. (2011). Lipid production of Chlorella vulgaris cultured in artificial wastewater medium. Bioresource Technology, 102(1), 101-105.
Harris, R., Harris, P., & James, A. (1965). The fatty acid metabolism of Chlorella vulgaris. Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 106(3), 466-473.
Home - Chlorella vulgaris C-169. (n.d.). Home - Chlorella vulgaris C-169. Retrieved April 30, 2014, from http://genome.jgi-psf.org/Chlvu1/Chlvu1.home.html
Liebke, F. (n.d.). Chlorella Vulgaris - Medicinal Food. Klinghart Academy. Retrieved April 28, 2014, from http://www.klinghardtacademy.com/Articles/Chlorella-Vulgaris-Medicinal-Food.html
Lim, S., Chu, W., & Phang, S. (2010). Use of Chlorella vulgaris for bioremediation of textile wastewater. Bioresource Technology, 101(19), 7314-7322.
Nichols, B. (1965). Light induced changes in the lipids of Chlorella vulgaris. Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 106(2), 274-279.
Wakasugi, T. (1997). Complete nucleotide sequence of the chloroplast genome from the green alga Chlorella vulgaris: The existence of genes possibly involved in chloroplast division. Proceedings of the National Academy of Sciences, 94(11), 5967-5972.
Yuvraj, Vidyarthi, A.S., & Singh, J. (2016). Enhancement of Chlorella vulgaris cell density: Shake flask and bench-top photobioreactor studies to identify and control limiting factors. Korean Journal of Chemical Engineering, 33(8), 2396-2405.
Page authored by David Wells, student of Prof. Jay Lennon at IndianaUniversity.