Valorization of corn steep liquor for efficient paramylon production using Euglena gracilis: The impact of precultivation and light-dark cycle

To achieve economic and efficient production of value-added materials from mixotrophic Euglena gracilis cultivation, utilizing a cost-effective substrate and optimizing the bioprocess factors are critical. In this study, the industrial byproduct corn steep liquor (CSL) was applied to the feasibility of its use and compared with a synthetic medium. The effects of precultivation trophic mode and light-dark (LD) cycle on cell growth, biomass, CO 2 biofixation, and paramylon production were investigated. The use of CSL enhanced both cell growth and biomass production by 1.5-fold. Biomass production using CSL was the highest in the photoautotrophically precultivated culture (3.69 g/L), while the highest paramylon content was observed in the heterotrophically precultivated culture (42.0%). Efficient paramylon production using CSL was accomplished by heterotrophic precultivation and applying the LD8:16 conditions. The highest CO 2 biofixation rate of E. gracilis was shown in the heterotrophically precultivated culture using CSL under LD16:8 (1.07 g/L/d). CO 2 biofixation rates using CSL were 2.8–6.4 fold higher than those using the synthetic medium. The valorization of the CSL promoted not only the bioconversion of CO 2 but also the production of value-added materials by E. gracilis.