Cultivation of Scenedesmus obliquus NCIM 5526 in a sol–gel transition medium for lipid production

Inefficient harvesting of microalgal biomass in large-scale cultivation is considered a grave issue to date. However, effective harvesting techniques and high throughput cultivation of biomass could be achieved by the cultivation of microalgae in the Tris–Acetate-Phosphate-Pluronic (TAPP) medium. TAPP media undergoes a thermo-reversible sol–gel transition, microalgae can be harvested gravimetrically by bringing the medium to the solution phase by decreasing the temperature to 15 °C and increasing the temperature by 7 °C (i.e., 22 °C) to induce gelation allowing the microalgal cells to form clusters rather than being isolated. Scenedesmus obliquus NCIM 5526 along with TAPP media grown in a sequential polybag reactor ensured a high economic and viable way of cultivation. Upon comparison, Scenedesmus obliquus grown in TAPP media was observed to have a higher specific growth rate (µ) of 0.398 d⁻¹ while a comparatively lower µ (0.321 d⁻¹) was witnessed in BG-11 media. The final biomass yield of 2.9 g/L and 2.2 g/L for TAPP and BG-11 media respectively was obtained at the end of 10 days. S. obliquus was observed to have a lipid content of 56.7% (w/w of DCW) in TAPP media. The lipid yield obtained was two-fold higher when cultivated in TAPP media (600 mg/L) while a lower yield was observed in BG-11 media (300 g/L). These results indicated that TAPP media was better suited for the cultivation of S. obliquus NCIM 5526. Thus, a highly efficient system and cost-effective technique for biomass cultivation are achieved by the use of TAPP media in a polybag photobioreactor.