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

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.

Photosynthetic nano fibers: Living microalgae packaging into polyvinyl alcohol nanofibers using an electrospinning method

“…Microalgae sizes range from a few micrometers to several 100 mm 24 . For example, Chlorella vulgaris , Pseudokirchneriella subcapitata , and Scenedesmus quadricauda measure 8–25 μm in diameter 24 . Conversely, larger species such as Pyrocystis lunula can reach diameters between 150 and 300 μm 24 .…”

“…This was in close agreement with the median measurement for microalgae, which was 11.3 μm. Microalgae sizes range from a few micrometers to several 100 mm 24 . For example, Chlorella vulgaris , Pseudokirchneriella subcapitata , and Scenedesmus quadricauda measure 8–25 μm in diameter 24 .…”

“…24 Conversely, larger species such as Pyrocystis lunula can reach diameters between 150 and 300 μm. 24 Based on the histogram data and considering the microalgae species used, we conclude that the spindles of approximately 10 μm in length incorporated into the nanofibers are indeed microalgae. This finding supports the idea that microalgae survived the high shear stresses encountered during field spinning and were encapsulated in an ultrathin PVA layer.…”

“…24 For example, Chlorella vulgaris, Pseudokirchneriella subcapitata, and Scenedesmus quadricauda measure 8-25 μm in diameter. 24 Conversely, larger species such as Pyrocystis lunula can reach diameters between 150 and 300 μm. 24 Based on the histogram data and considering the microalgae species used, we conclude that the spindles of approximately 10 μm in length incorporated into the nanofibers are indeed microalgae.…”

Growth of fungi and yeasts in food production waste streams: a bioremediation feasibility study

“…They also produce many industrially important enzymes and have a balanced amino acid pro le making it potentially nutritious [6,18]. Additionally, lamentous fungi can be used for various speci c purposes like occulating microalgae [19], providing a cheap alternative for microalgal harvesting, which is currently an expensive process [20]. Fungal cultivation in FPWS for various applications increases sustainability and develops the circular economy of food processing plants, furthering the EU's SDG 12.…”