Studies on Nannochloropsis oceanica: Global Transcriptome Profiling and Evaluation of Functional Implications of its EPA Rich Biomass to Ameliorate Liver Fibrosis

The current Ph.D. thesis explores the potential of EPA rich, N. oceanica as a sustainable and scalable source of EPA, a vital omega-3 fatty acid, to meet the escalating global demand for nutrient-rich, eco-friendly food sources. Whole-genome sequencing of N. oceanica using a hybrid Illumina–Nanopore approach yielded a high-quality ~30 Mb draft genome with complete chloroplast and mitochondrial sequences and 75.7% completeness. A total of 10,425 protein coding genes were predicted, with 88% functionally annotated. Comparative genomics with strains LAMB2011 and IMET1 showed 98.9% sequence identity. Cultivation optimization of N. oceanica in closed photobioreactors identified 1% CO₂, 160 μmol/m²/s light intensity, and white LEDs as optimal for EPA productivity (7.2 mg/L/day). Cold (10 °C) and dark stress, with transcriptome analysis indicating upregulation of fatty acid biosynthesis genes and repression of lipid degradation pathways. To improve EPA bioaccessibility in N. oceanica hindered by the algaenan-rich cell wall, high pressure homogenization (HPH) combined with polyethylene glycol alginate (PEA) was evaluated. Four-pass HPH with PEA significantly enhanced EPA bioaccessibility to 53.06%, compared to 44.7% with HPH alone. For therapeutic validation, EPA-rich N. oceanica biomass was orally administered to rats with CCl₄-induced liver fibrosis. High-dose treatment improved liver enzyme profiles, reduced fibrosis, and shifted gut microbiota toward SCFA-producing, anti-inflammatory bacteria (e.g., Blautia, Romboutsia, L. reuteri), highlighting gut-liver axis modulation. These results demonstrate the efficacy of N. oceanica biomass as a vegan, sustainable EPA source with potent hepatoprotective and microbiome-modulating effects, comparable to fish oil, underscoring its potential as a nutraceutical.<p></p>