Rare earth elements (REEs) have emerged as contaminants in water systems because their use and disposal are on the rise in many industries. To achieve environmentally benign treatment of REE-contaminated acidic water, we examined a strategy that uses Euglena gracilis for the bioremediation of REEs and simultaneous biodiesel production from used biomass. The presence of lanthanum (La3+) in the medium (0–100 µM) stimulated the growth of E. gracilis. The removal efficiency of La3+ was 99.9%, indicating that bioremediation using E. gracilis is feasible. The La3+ treatment accelerated the endocytic activity of E. gracilis and enabled cells to take up more nutrients (glucose and macro/micro elements). Also, La3+ increased the paramylon yield of E. gracilis, with the fatty acid methyl ester (FAME) yield below 3 wt% in both the control and La3+-treated cells. To increase the FAME yield and productivity, wax ester fermentation was conducted under anaerobic conditions. After wax ester fermentation, the FAME yield and productivity of the La3+-treated sample were 9.49 wt% and 78.76 g/L/day, 1.4- and 1.6-fold higher than the yield and productivity of the control sample. Moreover, the series of La treatment and wax ester fermentation enhanced the quality of biodiesel by increasing its saturated fatty acid (SFA) content. We confirmed that other REE species (cerium, neodymium, and a mixture) also stimulated the growth and biodiesel production of E. gracilis. Taken together, our E. gracilis-based bioremediation of REE-contaminated water provides high removal efficiency and a chance to simultaneously improve biodiesel productivity and quality.
Bibliographical noteFunding Information:
This study was supported by an NRF (National Research Foundation of Korea) grant funded by the Korean Government (MSIT; 2019R1A2C2087449 and NRF-2018-Global Ph. D. Fellowship Program). This work was also supported by Korea Environment Industry & Technology Institute (KEITI) through Project to develop eco-friendly new materials and processing technology derived from wildlife, funded by Korea Ministry of Environment (MOE) (2021003280004). This research was also supported by the Korea Basic Science Institute (KBSI) (Project No. C070300).
© 2022 Elsevier B.V.
- Heterotrophic cultivation
- Water treatment
- Wax ester fermentation
ASJC Scopus subject areas
- General Chemistry
- Environmental Chemistry
- General Chemical Engineering
- Industrial and Manufacturing Engineering