Isolation, Molecular Identification, and Lipid Productivity of Indigenous Chlorella sorokiniana under BG11, Algal Broth, and NPK Fertilizer Media: Implications for Low-Cost Biodiesel Feedstock Development in Northern Nigeria
TL;DR
The findings indicate that BG11 was the most effective medium under laboratory conditions, while algal broth may provide a practical alternative for further optimisation in freshwater microalgae cultivation.
Abstract
Microalgae are potential third-generation feedstocks for biodiesel production; however, region-specific information on indigenous strains and low-cost cultivation media remains limited in Northern Nigeria. This study isolated freshwater microalgae from aquatic environments within Abdullahi Fodio University of Science and Technology, Aliero, Kebbi State, Nigeria, and evaluated the growth and lipid productivity of selected Chlorella sorokiniana isolates cultivated in BG11, algal broth, and NPK fertiliser media. Eighteen water samples were collected from ponds, drainage water, runoff water, reservoir water, and botanical garden ponds. Microalgae were initially screened by microscopy, and selected Chlorella isolates were further characterised using ITS rRNA gene amplification, sequencing, BLAST comparison, and phylogenetic analysis. Cultures were maintained under controlled laboratory conditions at 25 ± 2°C with a 12:12 h light-dark cycle for 44 days. Biomass accumulation was monitored by dry cell weight, while lipids were extracted using the Bligh and Dyer method. Microscopic examination revealed Chlorella spp., Spirogyra spp., Chlamydomonas spp., Oedogonium spp., Microspora spp., Euglena spp., and Characium spp. Molecular analysis confirmed the selected isolates as Chlorella sorokiniana. BG11 supported the highest biomass production, with a final dry biomass of 35.48 g/L, a specific growth rate of 0.140 day⁻¹, and biomass productivity of 0.842 g/L/day. Algal broth produced intermediate growth performance, with final biomass of 19.61 g/L, a specific growth rate of 0.126 day⁻¹, and biomass productivity of 0.465 g/L/day. NPK medium produced the lowest values, with final biomass of 7.26 g/L, a specific growth rate of 0.102 day⁻¹, and biomass productivity of 0.170 g/L/day. The reported lipid contents were 27.07%, 23.13%, and 16.00% for BG11, algal broth, and NPK medium, respectively. The findings indicate that BG11 was the most effective medium under laboratory conditions, while algal broth may provide a practical alternative for further optimisation.