Effects of nitrogen and phosphorus limitation on lipid accumulation by Chlorella kessleri str. UTEX 263 grown in darknes
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Effects of nitrogen and phosphorus limitation on lipid accumulation by Chlorella kessleri str. UTEX 263 grown in darkness Nayan Shrestha 1 & Kiran K. Dandinpet 1 & Mark A. Schneegurt 1 Received: 14 November 2019 / Revised and accepted: 30 April 2020 # Springer Nature B.V. 2020
Abstract Growing algae in darkness for biodiesel production eliminates the challenges of evaporation and light penetration reported for open ponds and the costs and fouling that plague photobioreactors. The current study demonstrated that Chlorella kessleri str. UTEX 263 could grow heterotrophically in the dark on pure sugars or lignocellulosic hydrolysates of plant biomass. Hydrolysates of a prairie grass native to Kansas, Big Bluestem (Andropogon gerardii), supported the growth of C. kessleri in the dark. Nitrogen limitation stimulated the accumulation of biodiesel lipids by 10-fold in heterotrophic cultures grown on pure sugars or Big Bluestem hydrolysate. Limiting P in the growth medium also was shown to increase cellular lipid accumulation in C. kessleri. Iron limitation was not sufficient to increase cellular lipid content. Crude biomass extracts may have levels of N that cannot be easily removed, which are high enough to relieve N limitations in growth media. This initial study suggests that P might be more easily removed from biomass extracts than N for increasing cellular lipid production by nutrient limitation and further that native prairie grasses are potentially suitable as sources of lignocellulosic sugars. Keywords Algae . Biodiesel . Chlorophyta . Heterotrophy . Lipids . Starvation
Introduction Biofuels are renewable clean energy alternatives that might reduce CO2 emissions and mitigate global warming (Lincoln 2005; Demirbas 2009; Naik et al. 2010). Liquid fuels for transportation, manufacturing, and domestic heating represent nearly 70% of total global energy usage (Gouveia and Oliveira 2009). Food crops are commonly exploited as feedstocks to support production of biofuels by fungi or bacteria, which has raised sustainability concerns (Milne et al. 1990; Hill et al. 2006; Moore 2008; Brennan and Owende 2010; Havlík et al. 2011). Alternatively, manufacturers can utilize non-food lignocellulose feedstocks such as agricultural biomass, food processing wastes, forest residues, and grassy crops, as sources of sugars that can be liberated through enzymatic or acid hydrolysis. Biofuels produced by algae using the energy of sunlight offer an attractive alternative to biofuels
* Mark A. Schneegurt [email protected] 1
Department of Biological Sciences, Wichita State University, Wichita, KS 67260, USA
supported by land-based agriculture (Abou-shanab et al. 2006; Dragone et al. 2010; Smith et al. 2010; Verma et al. 2010; Lee and Lavoie 2013). Algae have been used to produce biofuels such as methane from anaerobic digestion of biomass, biodiesel from cellular lipids, and bio-hydrogen in photobioreactors (Belarbi et al. 2000). In general, the physical and fuel properties (density, acidity, and heating value) of biodiesel fr
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