Special Issue "Algae Fuel"

Guest Editor
Dr. Paul L. Chen
Center for Biorefining, Department of Bioproducts and Biosystems Engineering, University of Minnesota, 1390 Eckles Ave., St. Paul, MN 55108, USA
Website: http://www.tc.umn.edu/~chenx088/energy/
E-Mail: chenx088@umn.edu
Phone: +1 612 6257721
Interests: pyrolysis; hydrothermal liquefaction; microalgae; food processing

Dear Colleagues,

Fast growing, oil producing algae are recognized as one of the most promising biomass feedstock for production of biofuels and bioproducts. Despite the many advances made over several decades, commercialization of algal fuels remains challenging chiefly because of the techno-economic constrains and lack of understanding of life cycle impacts.  This special issue is to solicit high quality, original research contributions on all aspects of algae to fuels technologies, including but not limited to strain selection and development, cultivation techniques and facilities, harvest, downstream processing, product development, techno-economic analysis, and life cycle analysis.

Dr. Paul L. Chen
Guest Editor

Submission

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• algae
• microalgae
• biofuels
• biodiesel
• photobioreactor
• harvest
• conversion

Type of Paper: Communication
Title: Effects of light and temperature on fatty acid production in Nannochloropsis salina
Authors: Jon Van Wagenen, Tyler Miller, Sam Hobbs, Paul Hook, Braden Crowe and Michael Huesemann
Affiliation: Pacific Northwest National Laboratory, 1529 W Sequim Bay Rd. Sequim, WA 98382
Abstract: Accurate prediction of algal biofuel yield will require empirical determination of physiological responses to the climate, particularly light and temperature.  One strain of interest, Nannochloropsis salina, was subjected to ranges of light intensity (5 – 850 μmol m^-2 s^-1) and temperature (13-40 °C). The exponential growth rate, total fatty acids (TFA) and fatty acid composition were measured.  The maximum acclimated growth rate was 1.3 day^-1 at 23 °C and 250 μmol m ^-2 s^-1.  Fatty acids were detected by gas chromatography with flame ionization detection (GC-FID) after transesterification to corresponding fatty acid methyl esters (FAME).  A sharp increase in TFA containing elevated palmitic acid (C16:0) and palmitoleic acid (C16:1) during exponential growth at high light was observed, indicating likely triacylglycerol accumulation due to photo-oxidative stress.  Lower light resulted in increases in the relative abundance of unsaturated fatty acids; in thin cultures, increases were observed in palmitoleic and eicosapentaenoic acids (C20:5ω3).  As cultures aged and the effective light intensity per cell converged to very low levels, fatty acid profiles became more similar and there was a notable increase of oleic acid (C18:1ω9).  The amount of unsaturated fatty acids was inversely proportional to temperature, demonstrating physiological adaptations to increase membrane fluidity. These data will improve prediction of fatty acid characteristics and yields relevant to biofuel production.
Keywords: algae; biofuels; climate; fatty acid; Nannochloropsis salina

Title: Seasonal Variation of Lipids and Fatty Acids of the Microalgae Nannochloropsis oculata Grown in Outdoor Large-scale Photobioreactors
Authors: Martin Olofsson¹, Victória del Piño², Teresa Lamela², Jean Pascal Bergé³, Emmelie Nilsson¹, Pauliina Uronen^4, Catherine Legrand¹
Affiliations: ¹ Linnæus University, Kalmar, Sweden.
² Necton company, Ohlão, Portugal.
³ Ifremer, Nantes, France.
⁴ NESTE Oil, Finland
Abstract: Oil-producing microalgae are a potential feedstock for the biofuel industry but the dynamics of lipid production in mass cultivation outdoors are ambiguous. Seasonal variation of total lipids (TL) and fatty acid (FA) profiles in Nannochloropsis oculata grown outdoors in flat plate photobioreactors were analyzed from samples collected from May 2007 to May 2009 in Portugal. Lipid content ranged from 11 % of dry weight (DW) in winter to 30 % of DW in autumn. A positive significant relationship was found between light and temperature together and lipid content explaining more than 50 % of the variation. Highest lipid content was recorded during September-October, and suggests a possible rearrangement and enlargement of the photosynthetic apparatus at reduced light, which resulted in more structural lipids. Thus optimal lipid accumulation for N. oculata indicated a non-linear response to light and temperature. Although FA profiles of N. oculata varied over the year, a decrease in light and temperature during autumn coincided with an increased accumulation of monounsaturated fatty acids (MUFA) possibly at the expense of polyunsaturated fatty acids (PUFA). This indicated a synthesis of structural fatty acids in the form of MUFA as a consequence of a rearrangement in the photosynthetic apparatus during autumn at lesser light. The effect of relatively high temperatures on membrane fluidity may have lead to the formation of MUFA rather than PUFA.  We emphasize the role of environmental conditions governing lipid content and composition in microalgae. Seasonal and annual variations in TL and FA profile have to be considered for future estimation of oil yield in biofuel production.

Title: Use of Anion Exchanges Resins for one-step Processing of Algae from Harvest to Biofuel
Authors: Jessica Jones¹ and Martin Poenie²
Affiliations: ¹Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78712, USA
²Department of Molecular Cell and Developmental Biology, University of Texas at Austin, Austin, TX 78712, USA
Abstract: Some microalgae are particularly attractive as a renewable feedstock for biodiesel production due to their rapid growth, high content of triacylglycerols, and ability to be grown on non-arable land while maintaining a near neutral carbon footprint. Unfortunately, obtaining oil from algae is currently cost prohibitive in part due to the need to pump and process large volumes of dilute algal suspensions. In an effort to circumvent this problem, we have explored the use of anion exchange resins for simplifying the processing of algae to biofuel.  Anion exchange resins can bind and accumulate algal cells out of suspension to form a dewatered concentrate.  Treatment of the resin-bound algae with methanol-sulfuric acid elutes the algae and regenerates the resin while converting algal lipids to biodiesel. Hydrophobic polymers can remove biodiesel from the methanol-sulfuric acid, allowing the transesterification reagent to be reused.  We show that in-situ transesterification of algal lipids can efficiently convert algal lipid to fatty acid methyl esters (FAMEs) while allowing the resin and transesterification reagent to be recycled without loss of effectiveness.

Title: Microalgae Isolation and Selection Techniques for Prospective Biodiesel Production
Authors: Peer Schenk and Yan Li
Affiliation: School of Agriculture and Food sciences, The University of Queensland, Australia, E-Mail: p.schenk@uq.edu.au, y.li12@uq.edu.au
Abstract: Biodiesel production from microalgae is widely being developed at different scales as a potential source of renewable energy with both economic and environmental benefits. Although many microalgal species have been identified and isolated for lipid production, there is currently no consensus which species provides the highest productivity. Different species are expected to function best at different aquatic, geographical and climatic conditions. In addition, other value-add products are now being considered for commercial production which necessitates the selection of the most suitable algae strains suitable for multiple-products algal biorefineries. Here we present a practical guide to several simple and robust methods for microalgae isolation and selection for traits that maybe most relevant for commercial biodiesel production. A combination of conventional and modern techniques is likely the most efficient route from isolation to large-scale cultivation.

Title: High Lipid Induction in Microalgae for Biodiesel Production
Authors: Peer Schenk and Yan Li
Affiliation: School of Agriculture and Food sciences, The University of Queensland, Australia, E-Mail: p.schenk@uq.edu.au, y.li12@uq.edu.au
Abstract: Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competition for arable land or biodiverse natural landscapes. However, high costs due to low lipid productivity of fast-growing algae is one of the major bottlenecks hindering the commercial production of microalgal oil-derived biodiesel. Under optimal growth conditions, large amounts of algal biomass are produced but with relatively low lipid contents. Lipids, in the form of triacyl glycerides (TAG), typically provide a storage function in the cell that enables microalgae to endure adverse environmental conditions. Essentially, algal biomass and TAGs compete for photosynthetic assimilates and a reprogramming of physiological pathways is required to stimulate lipid biosynthesis. There has been a wide range of studies carried out on lipid induction techniques in microalgae such as the use of nutrient stress, including nitrogen and/or phosphorus starvation, osmotic stress, radiation, pH, temperature, heavy metals and other chemicals. In addition, several genetic strategies for increased TAG production and inducibility are currently being developed. In this review we discuss the potential of lipid induction techniques in microalgae and also their application in commercial scale.