Evaluation of Growth and Production of High-Value-Added Metabolites in Scenedesmus quadricauda and Chlorella vulgaris Grown on Crude Glycerol under Heterotrophic and Mixotrophic Conditions Using Monochromatic Light-Emitting Diodes (LEDs)

Abstract

This study aimed to examine the impact of crude glycerol as the main carbon source on the growth, cell morphology, and production of high-value-added metabolites of two microalgal species, namely Chlorella vulgaris and Scenedesmus quadricauda, under heterotrophic and mixotrophic conditions, using monochromatic illumination from light-emitting diodes (LEDs) emitting blue, red, yellow, and white (control) light. The findings indicated that both microalgae strains exhibited higher biomass yield on the mixotrophic growth system when compared to the heterotrophic one, while S. quadricauda generally performed better than C. vulgaris. In mixotrophic mode, the use of different monochromatic illumination affected biomass production differently on both strains. In S. quadricauda, growth rate was higher under red light (μmax = 0.89 d−1), while the highest biomass concentration and yield per gram of consumed glycerol were achieved under yellow light, reaching 1.86 g/L and Yx/s = 0.18, respectively. On the other hand, C. vulgaris demonstrated a higher growth rate on blue light (μmax = 0.45 d−1) and a higher biomass production on white (control) lighting (1.34 g/L). Regarding the production of metabolites, higher yields were achieved during mixotrophic mode in both strains. In C. vulgaris, the highest lipid (26.5% of dry cell weight), protein (63%), and carbohydrate (20.3%) contents were obtained under blue, red, and yellow light, respectively, thus indicating that different light wavelengths probably activate different metabolic pathways. Similar results were obtained for S. quadricauda with red light leading to higher lipid content, while white lighting caused higher production of proteins and carbohydrates. Overall, the study demonstrated the potential of utilizing crude glycerol as a carbon source for the growth and metabolite production of microalgae and, furthermore, revealed that the strains’ behavior varied depending on lighting conditions.

Produced water treatment by semi-continuous sequential bioreactor and microalgae photobioreactor

“…Most Scenedesmus species grow well under mixotrophic conditions. For example, Scenedesmus quadricauda exhibited a higher biomass yield when grown in mixotrophic conditions than its heterotrophic mode, aided by monochromatic illumination from light-emitting diodes (Korozi et al 2023 ). Similarly, Scenedesmus parvus achieved high biomass and demonstrated 81% COD and 19% BOD removal efficiency when cultivated in a mixotrophic mode (Ooi et al 2023 ).…”

Produced Water Treatment by Semi-Continuous Sequential Bioreactor and Microalgae Photobioreactor

“…have been observed to exhibit mixotrophic capabilities. For example, Scenedesmus quadricauda exhibited a higher biomass yield when grown in a mixotrophic mode compared to its heterotrophic mode with the aid of monochromatic illumination from light-emitting diodes [49]. In another study, Scenedesmus parvus achieved high biomass when cultivated in a mixotrophic mode.…”