Bioflocculation of Euglena gracilis via direct application of fungal filaments : a rapid harvesting method

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2022-02
Department
Department of Built Environment
Major/Subject
Mcode
Degree programme
Language
en
Pages
14
321-334
Series
JOURNAL OF APPLIED PHYCOLOGY, Volume 34, issue 1
Abstract
The high cost and environmental impact of traditional microalgal harvesting methods limit commercialization of microalgal biomass. Fungal bioflocculation of microalgae is a promising low-cost, eco-friendly method but the range of fungal and microalgal species tested to date is narrow. Here, eight non-pathogenic, filamentous fungi were screened for their ability to self-pelletize and flocculate Euglena gracilis (ca.50 µm motile microalga) in suspension. Self-pelletization was tested under various rotational speeds, and species which formed pellets (Ø > 0.5 cm) were selected for harvesting tests. Filaments of each species were combined with E. gracilis at various ratios based on dry weight. Harvesting efficiency was determined by measuring the change in cell counts over time, and settling of the flocs was evaluated by batch settling tests. Three fungal species, Ganoderma lucidum, Pleurotus ostreatus, and Penicillium restrictum, were able to reliably flocculate and harvest 62–75% of the microalgae while leaving it unharmed. The results demonstrated that self-pelletization, harvesting, and settling were dependent on the fungal species. The fungi to algae ratio also had significant but contrasting effects on harvesting and settling. In balancing the needs to both harvest and settle the biomass, the optimal fungi to algae ratio was 1:2. The application of fungal filaments to microalgae in suspension produced readily settling flocs and was less time-consuming than other commonly used methods. This method is especially attractive for harvesting microalgal biomass for low-value products where speed, low cost, and cell integrity is vital.
Description
Funding Information: Special thanks to the US Agricultural Research Service for the provision of fungal strains. Thanks also to Dr Marilyn Wiebe (Technical Research Centre of Finland) for her expert advice on fungi and Johanna Oja for her technical help. This research was enabled by funding from The Land and Water Technology Foundation, The Finnish Cultural Foundation, and The Finnish Foundation for Technology Promotion. Publisher Copyright: © 2021, The Author(s).
Keywords
Bioflocculation, Euglena gracilis, Filamentous fungi, Fungal pelletization, Microalgal harvesting
Other note
Citation
Bansfield, D, Spilling, K, Mikola, A & Piiparinen, J 2022, ' Bioflocculation of Euglena gracilis via direct application of fungal filaments : a rapid harvesting method ', JOURNAL OF APPLIED PHYCOLOGY, vol. 34, no. 1, pp. 321-334 . https://doi.org/10.1007/s10811-021-02651-5