The alga Bracteacoccus bullatus (Chlorophyceae) isolated from snow, as a source of oil comprising essential unsaturated fatty acids and carotenoids

Abstract

A unicellular alga isolated from snow in the Sierra Nevada Mountains (Spain) was characterised using a polyphasic approach. Comparative analysis of ITS2 rDNA secondary structures identified the new culture (CCALA 1120 Cepák and Lukavský Nova Hedwigia 94:163–173, 2012) as being conspecific with Bracteacoccus bullatus (Chlorophyceae). For the first time this study documented sexual reproduction as the pairing of gametes and also an-isogamy. Strain CCALA 1120 had a temperature optimum of growth about 21 °C and an irradiance optimum above 160 µmol photons m−2 s−1. It was cultivated in pilot-plant scale, using an open thin-layer photobioreactor in a greenhouse with only partial temperature control. After harvest, a high proportion of fatty acids was found (15.3% of dry mass) with linoleic (18:2ω-6) 18.3% and α-linolenic acids (18:3ω-3) 17.4% being the most abundant. Monounsaturated fatty acids accounted for about 30% with oleic (18:1ω-9) and vaccenic acids (18:1 ω-7) as the most prominent. The ratio of PUFA ω-6/ω-3 was 1:1.16, i.e. near to the ideal ratio of 1:1, as recommended by the World Health Organization. Biomass production was 2.67 g m–2 day−1 of dry weight, i.e. 0.2 g L−1 day−1. At the end of growth phase, total carotenoids made up 10.1 mg L−1. These results indicate that B. bullatus is suitable for production of a vegetable oil at lower temperatures (12–18 °C) and comprising a high content of unsaturated fatty acids.