The Aquatic Species Program was a relatively small research effort intended to look at the use of aquatic plants as sources of energy. Its history dates back to 1978, but much of the research from 1978 to 1982 focused on using algae to produce hydrogen. The program switched emphasis to other transportation fuels, particularly biodiesel, beginning in the early 1980's. This report summarizes the research activities carried out from 1980 to 1996, with an emphasis on algae for biodiesel production.

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Look Back at the U.S. Department of Energy's Aquatic Species Program: Biodiesel from Algae; Close-Out Report

Cyanobacteria have gained a lot of attention in recent years because of their potential applications in biotechnology. We present an overview of the literature describing the uses of cyanobacteria in industry and services sectors and provide an outlook on the challenges and future prospects of the field of cyanobacterial biotechnology. Cyanobacteria have been identified as a rich source of biologically active compounds with antiviral, antibacterial, antifungal and anticancer activities. Several strains of cyanobacteria were found to accumulate polyhydroxyalkanoates, which can be used as a substitute for nonbiodegradable petrochemical-based plastics. Recent studies showed that oil-polluted sites are rich in cyanobacterial consortia capable of degrading oil components. Cyanobacteria within these consortia facilitated the degradation processes by providing the associated oil-degrading bacteria with the necessary oxygen, organics and fixed nitrogen. Cyanobacterial hydrogen has been considered as a very promising source of alternative energy, and has now been made commercially available. In addition to these applications, cyanobacteria are also used in aquaculture, wastewater treatment, food, fertilizers, production of secondary metabolites including exopolysaccharides, vitamins, toxins, enzymes and pharmaceuticals. Future research should focus on isolating new cyanobacterial strains producing high value products and genetically modifying existing strains to ensure maximum production of the desired products. Metagenomic libraries should be constructed to discover new functional genes that are involved in the biosynthesis of biotechnological relevant compounds. Large-scale industrial production of the cyanobacterial products requires optimization of incubation conditions and fermenter designs in order to increase productivity.

Applications of cyanobacteria in biotechnology.

The limited fossil fuel prompts the prospecting of various unconventional energy sources to take over the traditional fossil fuel energy source. In this respect the use of hydrogen gas is an attractive alternate source. Attributed by its numerous advantages including those of environmentally clean, efficiency and renew ability, hydrogen gas is considered to be one of the most desired alternate. Cyanobacteria are highly promising microorganism for hydrogen production. In comparison to the traditional ways of hydrogen production (chemical, photoelectrical), Cyanobacterial hydrogen production is commercially viable. This review highlights the basic biology of cynobacterial hydrogen production, strains involved, large-scale hydrogen production and its future prospects. While integrating the existing knowledge and technology, much future improvement and progress is to be done before hydrogen is accepted as a commercial primary energy source.

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Hydrogen production by Cyanobacteria

Photobiological production of hydrogen

Microalgae are autotrophic microorganisms having extremely high photosynthetic efficiency and are valued as rich source of lipids, hydrocarbons, and other complex oils for biodiesel besides being an invaluable source of bioethanol, biomethane, and biohydrogen. Biodiesel produced from oilseed crops such as jatropha and soy have lower yields per unit land area and threaten food security. Indeed, microalgae have higher oil yields amounting to about 40 times more oil per unit area of land in comparison to terrestrial oilseed crops such as soy and canola. Further, microalgae production does not require arable land for cultivation. Biofuel is regarded as a proven clean energy source and several entrepreneurs are attempting to commercialize this renewable source. Technology for producing and using biofuel has been known for several years and is frequently modified and upgraded. In view of this, a review is presented on microalgae as second generation biofuel. Microalgal farming for biomass production is the biggest challenge and opportunity for the biofuel industry. These are considered to be more efficient in converting solar energy into chemical energy and are amongst the most efficient photosynthetic plants on earth. Microalgae have simple cellular structure, a lipid-rich composition, and a rapid rate of reproduction. Many microalgal strains can be grown in saltwater and other harsh conditions. Some autotrophic microalgae can also be converted to heterotrophic ones to accumulate high quality oils using organic carbon. However, there are several technical challenges that need to be addressed to make microalgal biofuel profitable. The efficiency of microalgal biomass production is highly influenced by environmental conditions, e.g., light of proper intensity and wavelength, temperature, CO2 concentration, nutrient composition, salinities and mixing conditions, and by the choice of cultivation systems: open versus closed pond systems, photobioreactors. Currently, microalgae for commercial purpose are grown mostly in open circular/elongated “raceway” ponds which generally have low yields and high production costs. However, a hybrid system combining closed photobioreactor and open pond is a better option. The biggest hurdle in commercialization of microalgal biofuel is the high cost and energy requirement for the microalgal biomass production, particularly agitation, harvesting, and drying of biomass. In order to conserve energy and reduce costs, algae are often harvested in a two-step process involving flocculation followed by centrifugation, filtration, or micro-straining to get a solid concentration. However, the major bottlenecks in algal biodiesel production within the cell can be identified and handled by adopting a system approach involving transcriptomics, proteomics, and metabolomics. Research and developments in the field of new materials and advanced designs for cultivation in closed bioreactors, use of waste water for biomass production, screening of efficient strains, high-value coproduct strategy, and cutting-edge metabolic engineering are thought to provide the biggest opportunities to substantially improve the cost effectiveness of such production systems.

/pdf/microalgae-as-second-generation-biofuel-a-review-36at1h1kaa.pdf

Microalgae as second generation biofuel. A review.

The growth of filamentous blue-green algae (FBGA) at high temperatures in outdoor, shallow solar ponds is being investigated. The temperature of the 60-m/sup 2/ ponds can be controlled to an average temperature of 45/sup 0/C. The growth of FBGA at high temperatures offers an opportunity, not presently available from outdoor algal ponds or energy farms, to obtain large amounts of biomass. Growth of algae at high temperatures results in higher yields because of increased growth rate, the higher light intensity that can be used before saturating the photosynthetic process, easier maintenance of selected FBGA strains, and fewer predators to decimate culture. Additional advantages of growing FBGA as a source of biomass include: bypassing the limitations of nutrient sources, because FBGA fix their own nitrogen and require only CO/sub 2/ when inorganic nutrients are recycled; toleration of higher salinity and metal ion concentrations; and easier and less expensive harvesting procedures.

Growth of filamentous blue-green algae at high temperatures: a source of biomass for renewable fuels

Anabaena cylindrica sparged with argon gas produced H2 continuously for 30 days under limited light conditions (6.0 W/m2) and for 18 days under elevated light conditions (32 W/m2) in the absence of exogenous nitrogen. The efficiency of converting visible light energy (32 W/m2) into chemical energy that is trapped as H2 ranged between 0.35 and 0.85% (approximately 13 microliter of H2 per mg [drywt] per h). Ammonium additions (0.2 mM NH4+) at various times destabilized the system and eventually suppressed H2 production completely, as compared with the control. Cultures grown with 5.0 mg of Fe3+ per liter produced H2 at a rate about twice that of cultures with 0.5 mg of Fe3+ per liter. Cultures grown at pH 7.4 produced H2 at the same initial rates as cultures that were grown at pH 9.4; however, the latter cultures continued to produce H2 after CO2 deprivation.

Hydrogen production by Anabaena cylindrica: effects of varying ammonium and ferric ions, pH, and light.

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Growth of filamentous blue-green algae at high temperatures: a source of biomass for renewable fuels

Hydrogen production by Anabaena cylindrica: effects of varying ammonium and ferric ions, pH, and light.