Bioresource potential of Tetradesmus obliquus UJEA_AD: critical evaluation of biosequestration rate, biochemical and fatty acid composition in BG11 media

BACKGROUND: Microalgae biomass is regarded as one of the most promising renewable biomass energy resources with the potential as a sustainable biological climate change mitigation agent, raw material for commercially valuable products and fossil fuel replacement. In view of that, this study isolated, identified and evaluated the potential of an indigenous freshwater green microalga strain, Tetradesmus obliquus UJEA_AD, collected from Emmarentia Dam, Johannesburg, South Africa. RESULTS: Morphological analysis and sequencing of the rbcL biomarker aided in identification of the isolate as T. obliquus. Tetradesmus obliquus UJEA_AD was further batch-cultivated autotrophically in BG11 medium and examined for biomass accumulation, CO₂ biofixation rate, biochemical composition and fatty acid production. The results showed a maximum biomass accumulation of 2.78 ± 0.019 g L⁻¹ with biomass productivity of 0.153 ± 0.001 g L⁻¹ day⁻¹ and specific growth rate of 0.13 ± 0.004 day^–1 as well as CO₂ biofixation rate of 0.265 ± 0.002 gCO₂ L⁻¹ day⁻¹. The biochemical data of the isolate revealed 27.17% ± 0.021% carbohydrate, 38.00% ± 0.15% protein and 31.2% ± 0.80% lipids; with primary fatty acids such as palmitic acid (34.26% ± 2.02%), linolenic acid (18.08 ± 5.29), trans-13-octadecenoic acid (12.32 ± 0.92) and phytol, 2-methylbutanoate (12.31 ± 1.02). CONCLUSION: These findings suggest that T. obliquus UJEA_AD is capable of producing bioproducts of economic value with an excellent CO₂ bio-mitigation potential when cultivated at optimum conditions in an autotrophic mode. Moreover, lipid extracted from T. obliquus UJEA_AD met the biodiesel quality standards of the USA and EU, making the isolate a promising commercial biodiesel feedstock.