Isolation and Screening of Indigenous Microalgal Strains from Diverse Ecological Niches for Lipid and Pigment Production Relevant to Sustainable Biorefinery Applications

Exploring microalgae diversity has been a longstanding endeavour for producing valuable metabolites with significant biotechnological applications. This study investigates the microalgal diversity present in three distinct agroecological zones of Kerala, each varying considerably in topography, rainfall patterns, and altitude. A total of 209 microalgae strains were identified from 19 selected sites, showcasing the richness of diversity across these regions. Furthermore, 30 microalgae strains belonging to chlorophyceae (16) and cyanophyceae (14) were isolated and screened for their lipid and pigment productivity potential. Among the Chlorophyceae, Coelastrella sp. exhibited the highest growth rate (0.096 µ/day), while Ankistrodesmus falcatus and Monoraphidium contortum demonstrated the highest lipid productivity (23.69–22.17 mg/L/day). Carotenoid productivity was notably higher in Chlorella spp. and Monoraphidium contortum (343–268 µg/L/day). Among the Cyanophyceae members, Arthrospira platensis showed the highest growth rate (0.110 µ/day), followed by Oscillatoria sp. (0.89–0.78 µ/day), both exhibiting significant phycocyanin productivity (11.7–2.9 mg/L/day). The phycoerythrin productivity was exceptionally high in Synechococcus sp. and Leptolyngbya sp. (3.4–1.7 mg/L/day). Additionally, Synechocystis sp. exhibited moderate carotenoid content (4.5–3.8 µg/mg), while heterocystous Nostoc sp. and Anabaena sp. showed promising protein content (30–35%). The study highlights the potential of these isolated strains as promising candidates for biofuel and pigment production and their integration into a microalgae-based biorefinery.