Effect of Nutrients on the Growth of a Hypersaline Diatom

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Effect of Nutrients on the Growth and Photosynthetic Ability of a Hypersaline Diatom -------------------------------------------------
Murdoch University
Caitlin May: 30981943
Effect of Nutrients on the Growth and Photosynthetic Ability of a Hypersaline Diatom -------------------------------------------------
Murdoch University
Caitlin May: 30981943

Introduction

Recently there has been an increase of interest in the industrial applications of microalgae, in particular diatoms, for producing high value products. Diatoms are a group of eukaryotic, unicellular microorganisms generally characterized by an exterior cell wall comprised of amorphous silica (Falciatore & Bowler, 2002). Diatoms constitute a large proportion of phytoplanktonic algae and are of high ecological relevance, as they are believed to be responsible for approximately 40% of marine primary productivity (Falciatore & Bowler, 2002; Young & Beardell, 2005). Over the past few decades numerous species of diatoms have been screened for their ability to produce natural substances such as poly-unsaturated fatty acids (fish oils), antibiotics, vitamins, hydrocarbons, pharmaceutically active compounds and foodstuffs for both human consumption and aquaculture industries (Bozarth et al., 2008; Cenciani et al., 2011; Converti et al., 2009). Of particular interest however are their fuel production capabilities, most notably their ability to produce large amounts of natural oils with some diatom species reported to produce a lipid content of between 20%- 40% dry weight (Jiang et al., 2012; Kanda et al., 2011; Liu et al., 2008). In addition to lipid production for biodiesels, diatom biomass also contains carbohydrates and proteins that can be used as alternate fuels via carbohydrate fermentation for ethanol, anaerobic digestion of proteins to produce methane and photobiological hydrogen production, making them a valuable resource for industrial applications (Bozarth et al., 2008; Cencani et al., 2011). In this regard it is believed that microalgae will play a major role in the mass production of biofuels and producing high value products over the coming years (Converti et al., 2009; Ramachandra et al., 2009). Microalgae are known as some of the most efficient photosynthetic organisms on earth, with both their growth and lipid production capabilities directly linked to reductions in greenhouse gas emissions (Cenciani et al., 2011; Feng et al., 2011). This presents further benefits for their use as a renewable energy source as they can potentially sequester carbon dioxide released from industrial plants during their growth, effectively acting as a carbon sink (Cenciani et al., 2011; Converti et al., 2009;). Due to these factors diatoms and other microalgae have emerged as one of the most promising alternatives for the production of renewable biofuels. This is largely due to their faster growth rates, photosynthetic efficiencies and higher oil yields in comparison to current terrestrial plant sources (Converti et al., 2009; Liu et al., 2008). Furthermore, microalgae are able to grow in areas not suited for conventional agriculture such as marginal lands, high salinity reservoirs and wastewater deposits, minimizing the displacement of farmland required for food crops (Liu et al., 2008). Although mass cultivation of microalgae is steadily increasing worldwide the use of microalgae biofuels is yet to be commercialized due to its relatively high cost in comparison to current fuel sources. Key parameters affecting algal oil production include biomass productivity, overall lipid productivity and downstream processing costs (Feng et al., 2011; Liu et al., 2008; Zhang et al., 2010). Thus, developments in process optimization will be a determining factor in the future of this technology. The overall cellular productivity and biochemical quality of lipids is largely dependent on microalgae growth conditions (Pahl et al., 2009). The quality and quantity of...
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