Enhancing growth and metabolite profiles in indigenous Euglena gracilis through explorative light spectrum effect

Microalgae offer numerous benefits, including the production of value-added products like omega-3 fatty acids, pigments, and bioactive compounds, as well as their potential use as a third-generation biofuel. Euglena, a unicellular microalgae, is gaining attention as an industrially relevant organism and an emerging cell factory. It exhibits various trophic growth types depending on cultivation conditions. Light intensity and wavelength are critical factors affecting microalgal growth and productivity. This study explores the effects of different light-emitting diode (LED) wavelengths on the growth models and metabolite production of Euglena gracilis from peatland water. The highest specific growth rates were observed under blue and white light in both the logistic and Gompertz models. White light produced the highest biomass yield (0.813 ± 0.261 g.L−1). Our findings indicate that white light is the most effective treatment for enhancing growth and metabolite content, including lipids, carbohydrates, paramylon, and carotenoids. Conversely, green light resulted in the highest protein content. Different illumination treatments led to variations in lipid profiles and fatty acid composition. The highest SFA content was recorded under red light (59.6%), while the highest PUFA content was observed under blue light (31.1%), and the highest MUFA content was detected under red light (18.0%). In conclusion, this study highlights the impact of LEDs on the growth models of E. gracilis and their influence on the production of biomass, carbohydrates, proteins, chlorophyll, carotenoids, paramylon, and fatty acids.