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

Abstract

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, CO2 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 CO2 biofixation rate of E. gracilis was shown in the heterotrophically precultivated culture using CSL under LD16:8 (1.07 g/L/d). CO2 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 CO2 but also the production of value-added materials by E. gracilis.