Bioprospecting wild South African microalgae as a potential third-generation biofuel feedstock, biological carbon-capture agent and for nutraceutical applications

Abstract

Microalgae are among the few biological resources studied that are found to possess vast biotechnological potential. This study isolated, identified and investigated two wild green microalgal species with substantial potential as a bioresource and climate change mitigation importance. Two isolates, Chlorella sorokiniana and Tetradesmus reginae were cultivated in selected artificial media under laboratory conditions. The isolates were analysed for nutrient consumption, biomass productivity, CO2 biosequestration rate, elemental composition and fatty acid methyl profiles/composition. The outcome showed maximum daily biomass productivity of 0.128 ± 0.003 and 0.2 ± 0.004 g L−1 for C. sorokiniana and T. reginae, respectively. CO2 biosequestration rate of T. reginae was the highest among the isolates, indicating that it can act as a biological climate change mitigation agent. Moreover, T. reginae recorded a significantly higher (p < 0.05) total lipid and carbohydrate content than C. sorokiniana. The C/N ratio for T. reginae was significantly higher than the C/N ratio for C. sorokiniana. Tetradesmus reginae also demonstrated the ability to produce a considerable quantity of omega-3 oils; hence, the species is of nutraceutical importance. Furthermore, T. reginae demonstrated maximal carbohydrate content and is therefore considered a potential feedstock for bioethanol production. Chlorella sorokiniana, on the other hand, showed a remarkable (p < 0.05) protein content making it a potential source for human food and animal feed supplement. Finally, the two isolates met both European and American quality biodiesel standards with exceptional cetane (CN) and iodine numbers (IV).

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.…”

“…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.…”

“…To determine the crude protein content of influent-treated strains, the biomass nitrogen contents of 4.27 ± 0.76 (T. obliquus), 3.65 ± 0.31 (C. sorokiniana) and 2.33 ± 0.41 (T. reginae) were multiplied by a factor of 4.78. 71 Other similar microalgal-based studies 26,72,73 exploited this factor.…”