Abstract
Nitrogen stress increases lipids content in microalgae, the main feedstock for algal biodiesel. Sodium tungstate was used in this study to implement nitrogen stress by inhibiting nitrate reductase (NR) in Dunaliella tertiolecta. The reduction of NR activity was accompanied by reduction of chlorophyll and accumulation of lipids. One-stage and two-stage culture strategies were compared. One-stage culture raised total lipids from 18% (control) to 39% (w: w); however, two-stage culture raised lipids to 50% in which neutral lipids were enhanced 2.14 times. To assess the quality of biodiesel produced, fatty acid methyl esters (FAME) composition was studied. It showed a slight variation of unsaturation. In addition, some physical proprieties of biodiesel were estimated and showed that higher heating values were improved by tungstate treatment. In this study, we tried to shed light on some biological impact of NR inhibition in microalgae cells using sodium tungstate which could be exploited in the improvement of biodiesel production.
Highlights
The increase of energy consumption during the previous century, the depletion of fossil fuels and the accumulation of greenhouse gases led to the emergence of renewable energies as promising alternative.Renewable energy provided an estimated 18.2% of global final energy consumption in 2016 [1]
The growth of D. tertiolecta was compared in one-stage culture, twostage culture and controls (Figure 1(a))
We showed that the addition of tungstate to the microalgal cultures led to a decrease of nitrate reductase (NR) activity in Dunaliella tertiolecta (Figure 2)
Summary
The increase of energy consumption during the previous century, the depletion of fossil fuels and the accumulation of greenhouse gases led to the emergence of renewable energies as promising alternative. Renewable energy provided an estimated 18.2% of global final energy consumption in 2016 [1]. Bioenergy is the largest renewable contributor to global final energy demand, providing nearly 13% of the total. Biodiesel is a bioenergy produced from a variety of sources. Microalgae are one of the most promising sources of biomass for biodiesel production thanks to their high lipid content [1]. Biodiesel from microalgae is not yet in the market due to its noneconomical viability at large scale. Some locks should be lifted starting by the improvement of growth rate and lipid content which are the key parameters of lipid productivity
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