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

In this study the use of Euglena gracilis biomass for ce.-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 +/- 0.14 g L-1 for heterotrophically to 3.4 +/- 0.02 g L-1 for photoautotrophically grown Euglena gracilis cells. The heterotrophically grown biomass accumulated product concentrations of 5.3 +/- 0.12 mg L-1 of alpha-tocopherol and 9.3 +/- 0.1 g L-1 of paramylon or 805 +/- 10.9 mL of biogas g(-1) (per gram volatile solids). The results for photoautotrophically grown cells were 8.6 +/- 0.22 mg L-1 of alpha-tocopherol and 0.78 +/- 0.01 g L-1 of paramylon or 648 +/- 7.2 mL of biogas g(-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. (C) 2015 Elsevier B.V. All rights reserved.