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

Abstract

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, CO 2 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 CO 2 biofixation rate of 0.265 ± 0.002 gCO 2 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 CO 2 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.

Evaluation of green microalgal strains for simultaneous municipal wastewater treatment and heavy metal bioremediation

“…Three wild microalgal strains were isolated from two freshwater bodies within Johannesburg, Gauteng, South Africa. 26,27 These strains were identified as Chlorella sorokiniana and Tetradesmus reginae from Killarney Country Club, 26 and Tetradesmus obliquus from Emmarentia Dam. 27 The strains were identified using both morphological (microscopic) and molecular (rbcL and ITS2 gene sequencing) analyses as previously depicted.…”

“…26,27 These strains were identified as Chlorella sorokiniana and Tetradesmus reginae from Killarney Country Club, 26 and Tetradesmus obliquus from Emmarentia Dam. 27 The strains were identified using both morphological (microscopic) and molecular (rbcL and ITS2 gene sequencing) analyses as previously depicted. 26,27 The microalgal strains under consideration were cultured in batches with the influent for a 16-day period at an illumination of 2000-2500 lx (Digital Lux Meter AS803, Arco Science & Technology Ltd, Guangzhou, China); 23 ± 3 °C and a light/dark cycle of 14/10.…”

“…27 The strains were identified using both morphological (microscopic) and molecular (rbcL and ITS2 gene sequencing) analyses as previously depicted. 26,27 The microalgal strains under consideration were cultured in batches with the influent for a 16-day period at an illumination of 2000-2500 lx (Digital Lux Meter AS803, Arco Science & Technology Ltd, Guangzhou, China); 23 ± 3 °C and a light/dark cycle of 14/10. Prior to cultivation, BG-11 media-based stock cultures of T. obliquus, C. sorokiniana and T. reginae were taken on the 8th day, centrifuged and washed twice with deionised water with the assumption that they were in the exponential growth stage.…”

Reclamation Potential of Onsite Wastewater Post-Treatment with Microalgae: Chemical Elements Perspective

“…External calibration by multi-element standard solution was performed. The concentrations of the elements were determined using the isotopes as follows: 31 P, 39 K, 42,44 Ca, 24,25,26 Mg, 32 S, determined as 48 SO in DRC mode, using oxygen as a reaction gas [51], 11 B, 63,65 Cu, 54,57 Fe, 55 Mn, 60,62 Ni, 64,66 Zn, 52 Cr, 107,109 Ag, 59 Co, 7 Li, 204, 206, 208 Pb, 110,112,114 Cd, and 75 As. The determination of the macro-elements P, K, Ca, Mg, Si, and Fe was performed in cell-based mode by optimization and application of an individual dynamic bandpass tuning parameter (RPa) for each isotope, as described in Lyubomirova et al, 2020 [52].…”

“…Although T. obliquus has been well-studied for its great biotechnological potential and high content of proteins, carbohydrates, lipids, and bioactive compounds [57,58], there is only a little data on the content of its inorganic compounds. A very recent study on T. obliquus strain RDLR01 biosorption of heavy metals from a tannery effluent after 15 days of treatment demonstrated their reduction in the following descending line of percentage: Cr-99.1%, Co-98.2%, Ni-97.4%, Cd-97.4%, Pb-94.3%, Zn-98.3% and Cu-96.3% [59].…”