The 2:00 session on Tuesday (2010-4-20) was on lignin modification in order to increase ethanol production efficiency in switchgrass (Panicum virgatum L.). The rationale for researching lignin was that lignin is a structural and physical barrier to polysaccharide degradation and they looked at switchgrass because it is a native species that would not harm biodiversity. Fu, Mielenz, Xiao, Hamilton, Chen, Bouton, Dixon, and Wang used transgenic methods to modify the biosynthesis of lignin and, by this, increase the bioconversion properties in switchgrass. They isolated the primary genes involved with lignin production (using PCR) and found that down regulation of a particular gene resulted in decreased lignin content. This, in turn, improved sugar recovery. They found that a lower S/G ratio was linked with carbohydrate conversion efficiency.
2010-4-20 Session on Lignin modification in Panicum virgatum L. by Fu, Mielenz, Xiao, Hamilton, Chen, Bouton, Dixon, and WangMay 6, 2010
Summary of the 1:00 session on the Genetic dissection of bioenergy traits in Sirghum by Vermerris, Saballos, Kresovich, Murray, Rooney, Pederson, Sattler, and XinMay 6, 2010
There has recently been a substantial amount of research done on sorghum as a biofuel feedstock because of its low water usage and fertilizer requirements. In the first session after lunch on Tuesday April 20, 2010, Vermerris, Saballos, Kresovich, Murray, Rooney, Pederson, Sattler, and Xin research on the genetics of sorghum was presented. They said that Sorghum is best known as a grain crop, but sweet sorghum is very similar to sugar cane in chemical composition. There is also forage sorghum. Sorghum plants are diploid, C-4, annuals that are produced from seeds; they have low-input requirements and a high yield potential. The genome has been sequenced. When sugar production is examined, sorghum “stacks up favorably against sugar cane and switchgrass,” according to the presentor. According to Vermerris et al., the ultimate goal in sustainable biofuel production is to minimize inputs and maximize outputs—this applies to grains, biomass, and sugar. They would ideally like to optimize crops to produce food, fodder, heat, biofuels, and biproducts.They said that sugar accumulation is poorly understood and that it depends on juice volume and cell wall modification. Their research is being done on several groups of Brown Rib Mutants; two of these mutants are the Bmr6 and the Bmr 2 mutants. Of the 19 Bmr mutants, Bmr 2 and Bmr 6 are the most promising for genetic modification. The mutants are being used because they are easier to convert to higher sugar yielding plants. There are 14 different copies of this one particular gene related to sugar production in sorghum, so it has taken them a long time to actually isolate it. Eventually, they succeeded. Vermerris et al. used several mapping techniques and then different cloning techniques in their research. The results will be published later this year.
The 11:00 session on Tuesday (2010-4-20) was about the development of microalgae as a biomass for biofuels. Micro aquatic crops such as duckweed, macroalgae, and microalgae are all currently being researched; this group of researchers, A. Darzins, L. Elliot, L. Laurens, E.J. Wolfrum, and M. Posewitz, is focused on microalgae. They mention the 30 year government study that researched algae based biofuels. This is the same government study that Ian Woertz talks about in his research article on algae based biofuels grown on wastewater streams. The government study ended in 1996. However, the program was essentially revived by the NREL in 2006. This study is continuing the research of that 30 year study. This new projects goal was to isolate and characterize microalgal strains utilizing high throughput techniques. They have research locations in Colorado, New Mexico, and several other locations elsewhere. Freshwater, brackish water, and saline/brine waters were brought back to the lab and they put one alga cell and 1 droplet into 96 well plate and allowed them to propagate themselves. High speed FACS sorting was utilized. They did clonal isolation and then used image positive brightfield microscopy. The green algae were found to be the most prominent, but many were fast growing. They currently think that the water vacuole in diatoms is lipids, but this remains a hypothesis for the time being. They are now working on a “bioprospecting project” using FACS, or florescence activated cell sorting. They are also studying high throughput methods for lipid extraction and identificaltion.
Estrogen is a female hormone that many people take in the form of medication. However, the human body never fully uses any medication and some of it passes through the body and is excreted. This estrogen, not used by humans, is carried in the waste stream to wastewater treatment plants. Unfortunately, most wastewater treatment plats have no way of removing. Without treatment, the estrogen flows through the plat, into streams or lakes where it is consumed by fish, frogs, and other amphibians. The animals that consume this estrogen are, not surprisingly affected by it; over time, these communities of fish and amphibians become more feminine—either by having higher percentages of females in the communities or by having feminine characteristics develop in males (this can occur to the extent of producing androgenous individuals).
A study conducted by Shi et al. was published in March of this year in Environmental Science and Pollution Research; they examined the fate of endocrine disrupting compounds (EDCs) in algae and duckweed wastewater treatment ponds (Shi et al., 2010). The EDCs 17α-ethinylestradiol (a synthetic estrogen compound), estrone (a naturally occurring estrogen form), and 17 β-estradiol (also naturally occurring) are commonly found in domestic sewage and were hence chosen for Shi et al.’s study (Shi et al., 2010). They used a species of Lemna duckweed (Shi et al., 2010). Several species of algae were used for the study including the following species: Anabaena cylindrical, Chlorococcus sp., Spirulina platensis, Chlorella sp., Scenedesmus quadricauda, and another Anaebena variant (Shi et al., 2010).
They conducted continuous-flow studies and batch tests (Shi et al., 2010). The batch test was carried out for 6 days; this time period, they found that algae or duckweed greatly helped with the removal of estrogens (Shi et al., 2010). The duckweed removed a higher percentage of estrogens than did the algae, but both were effective (Shi et al., 2010). Similar results were observed in the continuous-flow model. The continuous-flow system consisted of an initial pond and then two following tanks (Shi et al., 2010). The first pond was the most effective of these three: the duckweed first pond removed 85.4% of estrogens and the algae pond removed 76.8% (Shi et al., 2010). The following tanks removed 7.1 and 8.9 % for algae and duckweed respectively (Shi et al., 2010). Hence, the continuous-flow algae system removed a total of 83.9% of estrogens and the continuous-flow duckweed system removed 95.4% (Shi et al., 2010).
Some of the genera of algae studied here are also being studied by biofuel researchers. This system of wastewater treatment could be coupled with a biofuel production system.
Summary of “Extraction of Hydrocarbons from Microalga Botryococcus braunii with Switchable Solvents” by Samori et al.March 25, 2010
In a paper published in Bioresource Technology in 2010, Samori et al. examine a new procedure for extracting hydrocarbons from Botryococcus braunii. Botryococcus braunii is a species of colonial, freshwater, green, microalga that holds high potential as a renewable biofuel source. Samori et al. divide biofuels into first, second, and third generations. According to the authors of this study, ethanol from sugar cane or corn and biodiesel from seeds are considered first generation biofuels; lignocellulosic fuels based fuels are second generation fuels; and, algae/ microalgae based biofuels are the third generation. The rationale behind placing algal fuels at the forefront of biofuel sources lies in algae’s more efficient light usage, ability to grow in otherwise unusable areas, potential to multitask by cleaning up waste water flows, and ease of genetic modifications. Furthermore, biodiesel produced from algae tends to be more readily usable than biodiesel from seed plants. Drawbacks of algal fuel sources include energy intensive harvesting procedures and high economic costs from pond operation and bioreactors according to Samori et al. Despite these hindrances, algae-based biofuels are an upcoming and promising source of energy and as such, should be researched.
One of the most challenging aspects of biofuel production is the extraction of lipids or hydrocarbons from the fuel source. Samori et al. central focus was the comparison of two different SPS systems’ (DBU/ethanol and DBU/octanol), DBU’s, and n-hexane/chloroform/methanol’s lipid extraction efficiencies. An SPS is a switchable-polarity solvent that is based on DBU; DBU is an acronym for 1,8-diazabicyclo-[5.4.0]-undec-7-ene. They found that the alcohol used with the DBU is essential to assembling the liquid carbonate anion. Total hydrocarbon yield was greatest with DBU/octanol (16 ± 2%), second best with DBU alone (15 ± 6%), and third with DBU/ethanol (12 ± 2%); n-hexane yielded only 7.8% (± 3%). All DBU systems posted fatty acid extraction yields in the 0.6 to 0.7% range, while n-hexane/chloroform/methanol yielded around 2.7%. After 4 hours, DBU/octanol and DBU/ethanol yielded similar quantities of hydrocarbons—14% and 13%. The cycle between non-ionic and ionic was done by bubbling CO2 gas through equimolar solutions of DBU/octanol and changing DBU-octylcarbonate salt to its non-polar variant with N2 gas. A hydrocarbon extraction efficiency of 81% was achieved with ionic/ non-ionic cycling. Samori et al. concluded that SPS are promising as a “green technology” for hydrocarbon extraction from dried and aqueous growth microalgal. DBU/octanol had the highest extraction efficiency in both dried and liquid algae samples. SPS are also promising because they serve as a non-hazardous hydrocarbon extraction method for small biofuel production indistries.
Samori, Chiara, Cristian Torri Giulia Samori, Daniele Fabbri, Paola Galletti, Franca Guerrini, Rossella Pistocchi, and Emilio Tagliavin. 2010. “Extraction of hydrocarbons from microalga Botryococcus braunii with switchable solvents.” Bioresource Technology. 3274-3279.
A 2009 study by Converti et al. studied two species of microalgae: Nannochloropsis oculata and Chlorella vulgaris. Both are considered phytoplankton. These algae range in size from 2 micrometers to 4 micrometers and are photosynthetic, eukaryotic microorganisms. Their lipid content serves as a source for biodiesel. Temperature and nitrogen concentration typically play a vital role in the growth and production of plants and photosynthetic life forms. The two species were grown at a central temperature for a control; other tests were run at 5ْْ C. above and 5ْ C. below the middle temperature. Nannochloropsis oculata had a central temperature of 20ْ while Chlorella vulgaris had a central temperature of 30. An additional temperature experiment was performed on C. vulgaris at 38 degrees Celsius. Lipid production of N. oculata was tested at 0.300 gL-1, 0.150 gL-1, and 0.075 gL-1 of nitrogen. Lipid production of C. vulgaris was tested at nitrogen concentrations of 1.50 gL-1, 0.750 gL-1, and 0.375 gL-1. N. oculata lipid content virtually doubled (7.9 % to 14.92%) with the 5 degree increase from 20 to 25; C. vulgaris lipid content dropped from 14.71% to 5.90% with the temperature change from 25 to 30 degrees. Conversely, a 75% decrease in N concentration promoted lipid content production in both species: N. oculata content increased from 7.90 to 15.31% and C. vulgaris content increased from 5.90 to 16.41%.
Converti, Attilio, Allessandro Casazza, Erika Ortiz, Patrizia Perego, and Marco Del Borghi. 2009. Effect of temperature and nitrogen concentration on the growth and lipid content of Nannochloropsis oculata and Chlorella vulgaris for biodiesel production. Chemical Engineering and Processig. 48: 1146-1151.
Boysen et al. report acid fuel cells with higher performance through humidity stabilization in Science (2004), 303(5654): 68-70. Fuel cells are a possible solution for use in transportation, and involve an electrochemical reaction, which resembles the way a battery works. The difference between a fuel cell and a battery is that a battery can store energy internally, whereas a fuel cell needs a supply of reactant to keep it running. The fuel provided to the cell has its electrons and protons separated by catalysis, and the electrons then travel through a circuit, which converts them into electrical energy. There are many many different types of fuel cells, which use many different forms of catalysts.
Acid fuel cells are desirable because the heat generated by these fuels cells can be used in part to continue reactions, which makes the reactions more efficient and allows the radiator in cars to be smaller. Also, acid fuel cells do not require precise water supply measurements and worries because their reaction is anhydrous (this is not the case for polymer fuel cells). However, attempts at making fuel cells from acids (specifically superprotonic solid acids) has been difficult due to their solubility in water and their “poor mechanical behavior.” However, researchers have found that operating the fuel cells at over 100 degrees C has reduced these issues.
Water (or humidity, because water ceases to be in its liquid form at the temperatures it is being used at) is used to stabilize the reactions of the solid acid fuel cells, making them more efficient and more reliable.