Applicability of Euglena gracilis for biorefineries demonstrated by the production of α-tocopherol and paramylon followed by anaerobic digestion

•The suitability of E. gracilis for two novel different biorefinery concepts is demonstrated.•The biomass of E. gracilis is a highly productive substrate for anaerobic digestion.•Biogas yield of E. gracilis biomass depends on the age of the culture and on the cultivation mode.•Very high biogas yields can be expected even after α-tocopherol extraction. In this study the use of Euglena gracilis biomass for α-tocopherol, paramylon and biogas production in a value-added chain was investigated. Therefore, we analyzed the dry cell weight and product concentrations at different growth phases during heterotrophic, photoheterotrophic and photoautotrophic cultivation in a low-cost minimal medium. Furthermore, the specific biogas yields for differently derived biomass with and without product recovery were investigated. We demonstrate that growth phase and cultivation mode not only have a significant impact on product formation, but also influence the yield of biogas obtained from anaerobic digestion of Euglena gracilis biomass. The maximum dry cell weight concentration ranged from 12.3±0.14gL−1 for heterotrophically to 3.4±0.02gL−1 for photoautotrophically grown Euglena gracilis cells. The heterotrophically grown biomass accumulated product concentrations of 5.3±0.12mgL−1 of α-tocopherol and 9.3±0.1gL−1 of paramylon or 805±10.9mL of biogasgvs−1 (per gram volatile solids). The results for photoautotrophically grown cells were 8.6±0.22mgL−1 of α-tocopherol and 0.78±0.01gL−1 of paramylon or 648±7.2mL of biogasgvs−1. For an energy-saving downstream procedure the extracting agent methanol does not have to be removed strictly. Samples with residual methanol showed a significantly increased biogas yield, because the solvent can be used as an additional substrate for methane production by archaebacteria.