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

In this study, waste water samples from shrimp cultivation ponds in the central province of Ninh Thuan, Vietnam were used for the isolation of microalgae. As a result, a microalgal strain (nl6) was isolated and genetically identified. The blast search of the 18S rDNA-ITS region (2600 bp) against the known sequences on the NCBI database showed 100% identity with the sequence of an isolate of as Nannochloropsis salina (D12, accession number JX185299.1) from Shandong in China. The biomass was collected after 17 days of cultivation when the growth reached stationary phase with the highest biomass of 0.603 ± 0.07 g/L. Nannochloropsis salina nl6 was considered as 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 was in the range between C14 – C20 in which C16:0 was dominant with 33.43 ± 0.28% of total fatty acid (TFA) in log phase and 45.08 ± 2.05% TFA in stationary phase. Consequently, the saturated fatty acid content of strain nl6 was high with 42.76 ± 0.28 % TFA in log phase and 50.46 ± 1.85 % TFA in stationary phase. Salinity tolerance experiments (10, 20, 30 and 35 g NaCl/L) were also conducted and proved that strain nl6 was highly tolerant to salinaties used. The fatty acid profiles from different salinity treatments were relatively similar. Pigment analysis using HPLC-DAD showed the accumulation of astaxanthin (0.36 ± 0.03 mg/g DW) and cantaxanthin (0.18 ± 0.01 mg/g DW) in stationary phase when the nutrient in the culture was depleted.

This work has received funding from ARES (Académie de Recherche et d’Enseignement Supérieur) through the project Renewable.