Effects of different nitrogen sources and concentrations on starch and lipid biosynthesis by Desmodesmus insignis

Abstract:

[Objective] In order to improve biofuel production by Desmodesmus insignis, we studied the effect of different nitrogen sources and concentrations on the growth, total lipids, carbohydrate and starch accumulation of Desmodesmus insignis. [Methods] D. insignis was cultivated in basic general-11 medium containing 5 different initial nitrogen concentrations (3, 6, 9, 12 and 18 mmol/L) supplied in the form of sodium nitrate, ammonium bicarbonate and urea. Biomass was determined by dry weight, total lipids by gravimeter, and carbohydrates and starch by phenolsulfuric acid method. [Results] NaNO₃, NH₄HCO₃ and CO(NH₂)₂ were all suitable for the growth of D. Insignis. When 3 mmol/L NaNO₃ was used, the peak lipid content reached to 32.61% (d.w). The maximum content and productivity of carbohydrate and starch were 56.54% (d·w), 55.33% (d·w) and 0.24 g/(L·d), 0.23 g/(L·d) respectively, when 18 mmol/L NH₄HCO₃ was used. Urea could also obtain relative high content of biomass, total lipids, carbohydrates and starch. [Conclusion] Integrating these results with production costs, we could suggest ammonium bicarbonate and urea as nitrogen source at the concentration of 18 mmol/L.

Key words:Desmodesmus insigni;biomass;total lipid;carbohydrate;starch;volumetric productivity