Influences of Dissolved Inorganic Carbon and Nitrogen sources on Growth, Total Lipid Content and Calorific Value of Freshwater Oleaginous Microalga Ankistrodesmus falcatus (Corda) Ralfs

Abstract

Biofuel potentiality of a native Indian strain of the freshwater oleaginous microalgae A.falcatus was studied owing to its inherently high lipid content. Influences of media constituents, pH and nitrogen sources on growth (µ), total lipid (TL) content and calorific value (CV) were compared in batch culture. Bold basal medium was superior (µ = 0.498 d^-1, TL = 43.6% and CV = 23.6 kJ/g) than BG11 (µ = 0.385 d^-1, TL = 38.5% and CV = 19.3 kJ/g). Medium pH (≈ 7.0) and NaHCO₃ (30 mg/L), were found suitable for optimum growth at light intensity 35 µmol/m²/s, temperature 25 ± 2 ⁰C and 16 hrs light and 8 hrs dark diurnal cycles. NO₃^- instead of NH₄⁺ was preferred in the range KNO₃ > NaNO₃ > NH₄NO₃ > Urea, for maximal biomass and lipid production. Maximum biomass, TL and CV (80 mg/L DCW and 42.4% and 20.6 kJ/g respectively) were determined in medium containing KNO₃ (17.6 mM). A close correlation between increase in TL and CV was observed (r² = 0.994). With further augmentations of TL and improved biomass yield the native microalga strain could be a potent candidate for biofuel production.

DOI: http://dx.doi.org/10.5755/j01.erem.61.3.1423