Improved techniques to estimate cell density, pigments and neutral lipids in Nannochloropsis oculata CCALA 978 (Eustigmatophyceae) from South Atlantic

BONGIOVANI, N.; POPOVICH, C.; MARTÍNEZ, A.M.; FREIJE, H.; CONSTENLA, D.; LEONARDI, P.

ALGOLOGICAL STUDIES

ELSEVIER SCIENCE BV

Año: 2013 p. 3 - 16

0342-1120

Abstract The development of efficient, rapid and species-specific techniques is indispensable for assessing growth and neutral lipid yield in microalga cultures for biodiesel oil production. Nannochloropsis oculata is a small microalga with a thick cell wall. In vivo techniques to estimate cell density, chlorophyll a and neutral lipids are reported. A calibration curve of cell density versus optical density was obtained and validated at 540 nm, under different growth phases. A Nile Red fluorescence staining method was used to quantify neutral lipid content in nitrogen-stress cultures. The addition of 5% dimethyl sulfoxide enhanced 12.5 times the fluorescence signal efficiency. Besides, no significant differences were found in the lipid neutral content between traditional and triolein methods. In situ and synchronous fluorescence measurements allowed to estimate the neutral lipid content and then, to establish the optimum harvesting time. Thus, these procedures may be applied for a better monitoring mode of growth and neutral lipid accumulation in N. oculata?s cultures at a larger scale. Keywords: Nannochloropsis oculata, optical density, chlorophyll a, neutral lipids, Nile Red.