Far-Red Component Enhances Paramylon Production in Photoautotrophic Euglena gracilis

TL;DR

This study shows that adding far-red light improves paramylon production in the microalga Euglena gracilis during its stationary growth phase.

Contribution

A modular photobioreactor was developed to test the effect of different light conditions on paramylon production in E. gracilis.

Findings

Euglena gracilis showed varied growth and pigment composition under different light regimes.

Far-red light significantly enhanced paramylon production during the stationary phase.

Photosynthetic and respiratory functions were confirmed to be active under all tested light conditions.

Abstract

In recent years, microalgae have gained significant biotechnological importance as a sustainable source of various metabolites of industrial interest. Among these, paramylon, a polysaccharide produced by the microalga Euglena gracilis, stands out for its diverse applications in biomedicine and pharmaceuticals. E. gracilis is an adaptable secondary eukaryote capable of growing photoautotrophically, heterotrophically and mixotrophically. During photoautotrophic growth, varying light conditions impact biomass and paramylon production. To investigate the effects of varying illumination more thoroughly, we designed and built a modular photobioreactor that allowed us to simultaneously evaluate the photoautotrophic growth of E. gracilis under twelve different light conditions: seven single-spectrum lights (ultraviolet, royal blue, blue, green, red, far-red, and infrared) and five composite-spectrum lights (3000 K, 10,000 K, and 30,000 K white lights, amber light, and “Full-spectrum” light). The 24-day growing kinetics were recorded, and the growth parameters were calculated for each light regime. Both growth curves and pigment composition present differences attributable to the light regime used for cell culture. Additionally, photosynthetic and respiratory machinery functionality were proven by oximetry. Finally, our results strongly suggest that the far-red component enhances paramylon production during the stationary phase.

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