Enhanced growth and metabolite production from a novel strain of Porphyridium sp.

Microalgae are capable of generating numerous metabolites that possess notable biological activities and hold substantial promise for various industrial applications. Nevertheless, the taxonomic diversity of these photosynthetic microorganisms has not received thorough investigation. Using the 18S rRNA encoding gene, a recently discovered strain originating from the Tunisian coast (the governorate of Mahdia) was identified as a member of the Porphyridium genus. The growth response as well as the metabolite accumulation of Porphyridium sp. to different culture media (Pm, F/2, and Hemerick) was investigated over a period of 52 days. The highest biomass production was recorded with Pm medium (2 × 10⁷ cell/mL). The apparent growth rates (µ) and the doubling time (D_t) were about 0.081 day^-1 and 12.34 days, respectively. The highest chlorophyll a (0.678 ± 0.005 pg/cell), total carotenoids (0.18 ± 0.003 pg/cell), phycoerythrin (3.88 ± 0.003 pg/cell), and proteins (14.58 ± 0.35 pg/cell) contents were observed with F/2 medium. Cultivating Porphyridium sp. in both F/2 and Hemerick media yielded similar levels of starch accumulation. The Hemerick medium has proven to be the most suitable for the production of lipids (2.23% DW) and exopolysaccharides (5.41 ± 0.56 pg/cell).