Comparative analysis of diatom genomes reveals substantial differences in the organization of carbon partitioning pathways
by Sarah Smith
Co-authored with R. M. Abbriano and M. Hildebrand
A major challenge in the development of microalgal strains for large-scale production is the optimization of biomass... more A major challenge in the development of microalgal strains for large-scale production is the optimization of biomass accumulation and production of fuel-relevant molecules such as triacylglycerol. Selecting targets for genetic manipulation approaches will require a fundamental understanding of the organization and regulation of carbon metabolic pathways in these organisms. Functional genomic and metabolomics data is becoming easier to obtain and process, however interpreting the significance of these data in a physiological context is challenging since the metabolic framework of all microalgae remains poorly understood. Owing to a complex evolutionary history, diatoms differ substantially from many other photosynthetic organisms in their intracellular compartmentation and the organization of their carbon partitioning pathways. A comparative analysis of the genes involved in carbon partitioning metabolism from Thalassiosira pseudonana, Phaeodactylum tricornutum, and Fragilariopsis cylindrus revealed that diatoms have conserved the lower half of glycolysis in the mitochondria, the upper half of glycolysis (including key regulatory enzymes) in the cytosol, and several mitochondrial carbon partitioning enzymes. However, some substantial differences exist between the three diatoms investigated, including the translocation of metabolic pathways to different compartments, selective maintenance and horizontal acquisition of genes, and differential gene family expansions. A key finding is that metabolite transport between intracellular compartments is likely to play a substantial role in the regulation of carbon flux. Analysis of the carbon partitioning components in the mitochondria suggests an important role of this organelle as a carbon flux regulator in diatoms. Differences between the analyzed species are specific examples of how diatoms may have modified their carbon partitioning pathways to adapt to environmental niches during the diversification of the group. This comparative analysis highlights how even core central pathways can be modified considerably within a single algal group, and enables the identification of suitable targets for genetic engineering to enhance biofuel precursor production.
Ramachandra T V., Durga Madhab Mahapatra, Karthick B., Richard Gordon, 2009. Milking Diatoms for Sustainable Energy: Biochemical Engineering vs Gasoline Secreting Diatom Solar Panels.
Ind. Eng. Chem. Res., 2009, 48 (19), pp 8769–8788
In the face of increasing CO2 emissions from conventional energy (gasoline), and the anticipated scarcity of crude... more In the face of increasing CO2 emissions from conventional energy (gasoline), and the anticipated scarcity of crude oil, a worldwide effort is underway for cost-effective renewable alternative energy sources. Here, we review a simple line of reasoning: (a) geologists claim that much crude oil comes from diatoms; (b) diatoms do indeed make oil; (c) agriculturists claim that diatoms could make 10−200 times as much oil per hectare as oil seeds; and (d) therefore, sustainable energy could be made from diatoms. In this communication, we propose ways of harvesting oil from diatoms, using biochemical engineering and also a new solar panel approach that utilizes genomically modifiable aspects of diatom biology, offering the prospect of “milking” diatoms for sustainable energy by altering them to actively secrete oil products. Secretion by and milking of diatoms may provide a way around the puzzle of how to make algae that both grow quickly and have a very high oil content.
The place of diatoms in the biofuels industry
by Sarah Smith
Co-authored with M. Hildebrand (first author), A. K. Davis, J. C. Traller, and R. Abbriano, published in the journal 'Biofuels' in March 2012
In spite of attractive attributes, diatoms are underrepresented in research and literature related to the development... more In spite of attractive attributes, diatoms are underrepresented in research and literature related to the development of microalgal biofuels. Diatoms are highly diverse and have substantial evolutionarily-based differences in cellular organization and metabolic processes relative to chlorophytes. Diatoms have tremendous ecological success, with typically higher productivity than other algal classes, which may relate to cellular factors discussed in this review. Diatoms can accumulate lipid equivalently or to a greater extent than other algal classes, and can rapidly induce triacylglycerol under Si limitation, avoiding the detrimental effects on photosynthesis, gene expression and protein content associated with N limitation. Diatoms have been grown on production scales for aquaculture for decades, produce value-added products and are amenable to omic and genetic manipulation approaches. In this article, we highlight beneficial attributes and address potential concerns of diatoms as biofuels research and production organisms, and encourage a greater emphasis on their development in the biofuels arena.
Adam M. Posthuma (2009) Algae Biofuel Production - Master Thesis - Sustainable Development; Landuse, Ecosystems and Biodiversity
Optimizing Production and Environmental Assessment of Algae Biofuel.
Creative Commons licence.
Microalgae biomass is suggested as a more sustainable feedstock for biofuel production than conventional biofuel... more
Microalgae biomass is suggested as a more sustainable feedstock for biofuel production than conventional biofuel crops. Algae biodiesel yields are likely to be between 3 and 30 times higher than 1st generation biofuel crops. Other advantages of algae cultivation are: no dependence on arable land, low nutrient losses and related emissions, possibility of using sea and waste water resources and the possibility of flue gas CO2 and NOx recycling. Cultivation depends on various aspects such as light, nutrient and carbon availability and competition with other species and is generally done in open ponds or closed bioreactors. Closed systems have higher yield due to better control and optimization but also have higher investment cost. Combination of both open and closed systems into a hybrid system is argued to have better overall feasibility. Several options exist for biological optimization of the process. This study confirms a high throughput method for fluorometric quantification of algae lipid content, which could possibly be used to increase lipid content by selective breeding. Moreover, it is shown that treated sewage waste water can be used directly for successful algae cultivation. Furthermore, an analysis of land, energy, water and CO2 requirements and emissions related to all major aspects of cultivation and biomass conversion suggest that net energy balance (NEB) ratios of 5.0 and 3.7 and 5.1 can be obtained for open, closed and hybrid systems respectively, which is slightly lower than ratios for sugarcane (7.0) and palm oil (7.9), but higher than those for corn (1.3) and soybean (1.9). The overall spatial energy gain, or spatial NEB, is as high as 56, 100 and 80 MJ m-2 y-1 for the 3 systems respectively which is considerably higher than any of the conventional biofuel crops. Fresh water requirements are
considerable (±0.9 m3/liter biodiesel) for open systems but this is still a factor 2-3 lower than irrigation water used for typical biofuel crops. Compared to fossil diesel combustion, reduction in
CO2 emissions were as high as 81% and 88% for open and closed systems respectively. Sensitivity analyses showed that modeled uncertainties had considerable impact on overall energy balances, but were within acceptable range, confirming the validity of the results.
Download (.pdf) A Solar Photobioreactor for the Production of Biohydrogen from Microalgae
Co-authored with Luis Pantí, Pedro Chávez, Rodrigo Patiño
The green microalga Chlamydomonas reinhardtii is proposed to produce hydrogen in a low-cost system using the solar
radiation in Yucatan, Mexico. A two-step process is necessary with a closed photobioreactor, in which the algae are
firstly growth and then induced for hydrogen generation. Preliminary results are presented in this work with some
planning for the future. Different culture broths, temperatures and light intensities were tested for biomass and hydrogen
production in laboratory conditions. The first experiments in external conditions with solar radiation and without
temperature control have been performed, showing the potential of this technique at larger scales. However, some
additional work must be done in order to optimize the culture maintenance, particularly in relation with the temperature
control, the light radiation and the carbon dioxide supply, with the idea of keeping an economic production.
Production of biodiesel from microalgae
In recent years, biofuels have the prospects of providing alternative substitute to ever increasing demand of... more
In recent years, biofuels have the prospects of providing alternative substitute to ever increasing demand of conventional fuels. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However the food grain based ethanol production is constrained due to increased food demand which calls for concentrated R& D efforts to convert lingo cellulosic biomass feedstocks to alcohol. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from nonfood crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Presently biodiesel production using non- edible seed oil crops like Jatropha, pongamia, mahua etc is being given top priority to produce substitute to diesel fuel.
Based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO2, N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products.
Micro- algae is getting renewed interest for its production with regards to its oil extraction and biodiesel production and it is expected to provide enormous possibility to be used as feedstocks for biodiesel production on massive scale in near future because it does not complete with existing food production issue.
The present paper attempts are made to review the different species of algae having potential of high oil production and technologies used for growing, harvesting and extraction of oil. The work done so far nationally and internationally on biodiesel production issuing algae is reviewed and presented in the paper.
Shotgun proteomic analysis of the unicellular alga Ostreococcus tauri.
by Sarah Martin
Journal of Proteomics
Le Bihan T, Martin SF, Chirnside ES, van Ooijen G, Barrios-Llerena M, O'Neill JS, Shliaha PV, Kerr LE, Millar AJ.
Ostreococcus tauri is a unicellular green alga and amongst the smallest and simplest free-living eukaryotes. The O.... more Ostreococcus tauri is a unicellular green alga and amongst the smallest and simplest free-living eukaryotes. The O. tauri genome sequence was determined in 2006. Molecular, physiological and taxonomic data that has been generated since then highlights its potential as a simple model species for algae and plants. However, its proteome remains largely unexplored. This paper describes the global proteomic study of O. tauri, using mass spectrometry-based approaches: phosphopeptide enrichment, cellular fractionation, label-free quantification and (15)N metabolic labeling. The O. tauri proteome was analyzed under the following conditions: sampling at different times during the circadian cycle, after 24h of daylight, after 24h of darkness and various nitrogen source supply levels. Cell cycle related proteins such as dynamin and kinesin were significantly up-regulated during the daylight-to-darkness transition. This is reflected by their higher intensity at ZT13 and this transition phase coincides with the end of mitosis. Proteins involved in several metabolic mechanisms were found to be up-regulated under low nitrogen conditions, including carbon storage pathways, glycolysis, phosphate transport, and the synthesis of inorganic polyphosphates. Ostreococcus tauri responds to low nitrogen conditions by reducing its nitrogen assimilation machinery which suggests an atypical adaptation mechanism for coping with a nutrient-limited environment.
The production of the sesquiterpene β-caryophyllene in a transgenic strain of the cyanobacterium Synechocystis.
Reinsvold, Robert E., Jinkerson, Robert E., Radakovits, Randor., Posewitz, Matthew C., and Basu, Chhandak. (2011) Journal of Plant Physiology. 168: 848-852.
The plant secondary metabolite, β-caryophyllene, is a ubiquitous component of many plant resins that has traditionally... more The plant secondary metabolite, β-caryophyllene, is a ubiquitous component of many plant resins that has traditionally been used in the cosmetics industry to provide a woody, spicy aroma to cosmetics and perfumes. Clinical studies have shown it to be potentially effective as an antibiotic, anesthetic, and anti-inflammatory agent. Additionally, there is significant interest in engineering phototrophic microorganisms with sesquiterpene synthase genes for the production of biofuels. Currently, the isolation of β-caryophyllene relies on purification methods from oleoresins extracted from large amounts of plant material. An engineered cyanobacterium platform that produces β-caryophyllene may provide a more sustainable and controllable means of production. To this end, the β-caryophyllene synthase gene (QHS1) from Artemisia annua was stably inserted, via double homologous recombination, into the genome of the cyanobacterium Synechocystis sp. strain PCC6803. Gene insertion into Synechocystis was confirmed through PCR assays and sequencing reactions. Transcription and expression of QHS1 were confirmed using RT-PCR, and synthesis of β-caryophyllene was confirmed in the transgenic strain using GC-FID and GC–MS analysis.