Isolation and characterization of a Nannochloropsis salina isolate from Vietnam with potential for biodiesel production

In this study, a microalgal strain (nl6) has been isolated in Ninh Thuan province of Vietnam. The 18S rDNA-ITS region (2600 bp) was sequenced, blasted against the NCBI database and found 100% identical with the sequence of an isolate of Nannochloropsis salina (D12, accession number JX185299.1) from Shandong in China. The biomass obtained at log and stationary phase was 0.151 ± 0.005 g/L and 0.603 ± 0.07 g/L, respectively. Fatty acid analysis showed that Nannochloropsis salina nl6 is an oleaginous microalga with fatty acid content of 18.65 ± 1.04 % biomass dry weight (DW) in log phase and 18.17% ± 2.67 % DW in stationary phase. The chain length of fatty acid ranges between C14 – C20. C16:0 is dominant with 33.43 ± 0.28% of total fatty acid (TFA) in log phase and 45.08 ± 2.05% TFA in stationary phase. This leads to the high accumulation of saturated fatty acid in log phase (42.76 ± 0.28 % TFA) and stationary phase (50.46 ± 1.85 % TFA). Saturated fatty acids content is one of the main factors contributing to the fuel properties because higher amount of them will increase the cetane number in fuel. A salinity tolerance experiment has been performed by making growth curves at different salt concentrations (10, 20, 30 and 35 g NaCl/L). Results indicate that Nannochloropsis salina nl6 is highly tolerant to the different salinities analyzed and that the fatty acid profiles are relatively similar. The pigment profile analyzed by HPLC-DAD shows the accumulation of astaxanthin (0.36 ± 0.03 mg/g DW) and cantaxanthin (0.18 ± 0.01 mg/g DW) in stationary phase when nutrient deprivation occurs.

This work was supported by ARES (Académie de Recherche et d’Enseignement Supérieur) under the project Renewable.