The present study aimed to isolate and evaluate a local Protosiphon sp. for biodiesel production and antioxidant activity of its residual lipid-free biomass. Phylogenetic analysis confirmed that the isolate is Protosiphon botryoides. In the control medium using 250 mg L-1 NaNO3 as a nitrogen source, cells showed 37.7 dw% lipid content at stationary phase. At different nitrogen levels, increasing of nitrogen concentration resulted in obvious increase in growth, showing the maximum biomass productivity of 0.133 g L-1d-1at middle exponential phase using 750 mg L_1 NaNO3, with simultaneous reduction in lipid content, reaching its lowest recorded value of 27.9 dw%. Due to enhancement of lipid content of N deficient culture (125 mg L-1 NaNO3), it showed the highest lipid productivity of 41.3 mg L-1d-1. Fatty acid analysis confirmed the dominance of linoleic acid, eicosatrienoic acid, oleic acid, and palmitic acid. Biodiesel characteristics complied with the international standards and showed better properties than some other reported biodiesel promising microalgae. In addition, lipid-free biomass showed high radical scavenging activity of 55.3%, which confirms its suitability as additional nutritional and pharmaceutical material for enhanced biomass valorization. |
