Characterization of endolithic cyanobacterial strain, Leptolyngbya sp. ISTCY101, for prospective recycling of CO2 and biodiesel production

•An endolithic cyanobacterium Leptolyngbya ISTCY101 was isolated from marble rock.•Strain showed desirable growth attributes with high CO2 and salinity tolerance.•Increased biomass productivity and easy harvesting in mesh incubator.•Suitable fatty acid profile for biodiesel production.•The study opens up new avenues for exploring potential strains for CO2 recycling. The present investigation evaluates the potential of an endolithic cyanobacterium isolated from marble rock to utilize sodium bicarbonate (NaHCO3) as carbon source for prospective recycling of CO2 into biodiesel. Microalgae thriving on marble were cultured and subjected to increasing NaHCO3 concentration. The most competent isolate was identified and characterized in terms of growth, lipid content and fatty acid profile. A semicontinuous mesh incubator was designed for biofilm development. Isolate ISTCY101 was identified as Leptolyngbya sp. by 16S rRNA sequencing. Leptolyngbya ISTCY101 efficiently used BG-11 (50mM NaHCO3) and artificial seawater medium (25gL−1 NaCl) with biomass productivity 78.9 and 75.74mgL−1d−1, respectively. Maximum areal biomass productivity of 2.01gm−2d−1 was recorded in the mesh incubator, with complete exclusion of centrifugation for harvesting. Lipid content varied from 16% to 21%, consisting predominantly of C16:0, C16:1, C18:0, C18:1 fatty acids (>60%) making promising feedstock for biodiesel production.