A NOVEL MARINE NANNOCHLOROPSIS SP. (CHLOROPHYTA) ABLE TO PRODUCE BIOMASS AND LIPIDS IN ACIDOPHILIC CONDITION

Microalgae are potentially valuable biological mitigators of carbon dioxide due to their ability to convert it into biomass, that may be utilized to obtain lipids useful in a variety of biotechnological applications. In this study, we evaluated the ability of the new microalgal strain 72 to sequester atmospheric CO2 and produce biomass and lipids at different pH values (5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, and 9) in autotrophic conditions. The strain was cultivated in F/2 medium at 25 °C for eight days, under continuous artificial illumination with a light intensity of 100 µmol photons m-2 s-1, and continuously bubbled with atmospheric air. As resulted by the phenotypic and genotypic (18S rRNA gene sequencing) characterization, strain 72, isolated from water sample collected from the Strait of Messina (Italy), was related to the family of Monodopsidaceae (Chlorophyta) and attributed to Nannochloropsis salina CCMP1776 (98.08% similarity), a microalga widely distributed in the marine environment. At the optimal pH 6, strain 72 fixed 0.29 g L-1 d-1 of CO2 and produced higher biomass (1.22 g L-1) and more rapidly (eight days rather than 14 days) than N. oculata strain K-1281 (0.39 g L-1). Moreover, the lipids yield of strain 72 (21±3%) was higher than that reported for strain K-1281 (15%). The fatty acid profile was principally constituted by saturated fatty acids (55%), mainly represented by palmitic acid (37%), and monounsaturated oleic acid (25%) whose yield was higher than that of strain K-1281 (13%). Strain 72 could be useful in developing carbon capture technologies in acidic, CO2-rich environments. Due to its richness in oleic acid, a major essential component of human and animal diet, strain 72 could be a promising candidate for production of high-value human and animal foodstuffs and additives.