Sustainable cultivation of microalgae <i>Euglena</i> sp. IDN 22 using anaerobic digested manure wastewater: Integrating circular bioeconomy principles in agroindustry

This research was conducted by utilizing anaerobic digested manure wastewater (ADMW) as a growth medium for microalgae Euglena sp.IDN 22.This research aimed to determine the effectiveness of using ADMW as a rich nutrient supplement to cultivate microalgae Euglena sp.IDN 22. Multiple dilutions of 0%, 25%, 50%, and 75% were applied to ADMW, and the growth of Euglena sp.IDN 22 was analyzed using the growth rate of microalgae cell counts.The number of cells was observed with a haemocytometer.The cultivation of Euglena sp.IDN 22 in the ADMW medium was conducted in lab-scale (1 L) photobioreactors for 15 days of cultivation.The analysis of 25% ADMW showed C/N and P/N of 7.40 0.17 and 1.27 0.03, while 50% ADMW analysis yielded 14.99 0.51 and 1.72 0.07.The best growth rate trend of Euglena sp.IDN 22 in ADMW was shown by the treatment with 25% ADMW dilution with a maximum growth of 62.92 10 4 cells/ml, compared to a maximum growth of 79.92 10 4 cells/ml with 0% ADMW as a control.Slow growth activity was shown by 50% and 75% ADMW, with a maximum growth of only 10.67 10 4 cells/ml and 4.45 10 4 cells/ml, respectively.The slow growth activity in 50% ADMW, with a maximum growth of only 10.67 10 4 cells/ml, demonstrated a significant difference (p > 0.01).The results of this study prove that the integration of 25% ADMW and Euglena sp.IDN 22 cultivation can be an effective valorization concept and an opportunity to transform biogas production waste towards a circular economy in agroindustry.