Microalgae harvesting by fungal-assisted bioflocculation

Nazari, Mateus Torres; Freitag, João Felipe; Cavanhi, Vítor Augusto Farina; Colla, Luciane Maria

doi:10.1007/s11157-020-09528-y

Cited by 36 publications

(19 citation statements)

References 126 publications

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“…When P. ostreatus was added to E. gracilis at four different ratios, fungal dose and harvesting efficiency were positively correlated aligning with earlier findings (Li et al 2020;Nazari et al 2020). Harvesting efficiency at the lowest fungal ratio was 10-13% lower than for the other ratios which had similar removal rates, suggesting a minimum fungal inoculum concentration threshold for optimal microalgal harvesting.…”

Section: Harvesting Efficiencysupporting

confidence: 85%

“…The smallest (8-25 µm), non-motile, microalgae (Chlorella vulgaris, Pseudokirchneriella subcapitata and Scenedesmus quadricauda) had the highest flocculation rates (up to ~ 90% in 24 h) while the largest (150-300 µm), non-motile, microalgae (Pyrocystis lunula) had the lowest flocculation rate (up to ~ 40% in 24 h). The results from our study suggest that large motile microalgae may not be harvested by fungal bioflocculation, either as filaments or pellets, as efficiently as smaller non-motile species (Ummalyma et al 2017;Nazari et al 2020). In a method similar to ours, Talukder et al (2014) applied exogenous fungal filaments to immobilize C. vulgaris and Nannochloropsis spp., which are small (≤ 10 µm) non-motile algae.…”

Section: Harvesting Efficiencymentioning

confidence: 74%

“…The short life span of T. versicolor flocs indicates that T. versicolor may quickly destabilize and flocculate microalgae via weaker bonding types, such as charge differences and entrapment, but produce insufficient EPS which are fundamental to the formation and structural maintenance of flocs (Nazari et al 2020). The slight decrease in harvesting efficiency for all species after T max indicates that some E. gracilis cells "escaped" the fungi back into suspension, which could be due to charge difference, which is not enough alone to keep motile microalgae attached to fungal filaments as suggested by Egede et al (2016).…”

Section: The Interaction Between Flocculation and Harvestingmentioning

confidence: 99%

“…Fungi employ, often simultaneously, several different microalgal harvesting mechanisms such as self-pelletization, excretion of EPS, attraction, entrapment (Egede et al 2016;Magdouli et al 2016), and attachment to the fungal cell wall (Wrede et al 2014;Du et al 2018). However, fungi are more attractive bioflocculants than bacteria because of their higher harvesting efficiencies (Zhou et al 2012;Li et al 2020;Nazari et al 2020), greater potential to improve total biomass yields and value due to their nutrient, enzyme, and biochemical content (Egede et al 2016;Li et al 2020), and larger, denser flocs (Nguyen et al 2019;Zhao et al 2019;Kim et al 2020;Pei et al 2021). Bacteria-microalgae flocs tend to be < 5 mm and less dense (Lee et al 2013;Nguyen et al 2019;Kim et al 2020;Pei et al 2021), while fungi-microalgae flocs have more densely packed structure and may grow to be > 5 mm (Zhao et al 2019;Kim et al 2020) improving settling and dewatering of the biomass (Benjamin and Lawler 2013).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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.

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Section: Harvesting Efficiencysupporting

confidence: 85%

Section: Harvesting Efficiencymentioning

confidence: 74%

Section: The Interaction Between Flocculation and Harvestingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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“…Harvesting by centrifugation or filtering leads to higher efficiency, but these methods are not suitable for continuous culture (Shelef et al, 1984;Najjar and Abu-Shamleh, 2020). Continuous culture and sediment harvesting can reduce the time and cost associated with bioresource production (Park et al, 2011(Park et al, , 2015Nazari et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Enhancement of Biomass Production in Colony-Forming Green Algae, Botryosphaerella sudetica, Under Mixotrophic Cultivation

2021

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In this study, we characterized the potential of colony-forming green algae, Botryosphaerella sudetica KNUA107, isolated from Ulleung Island, South Korea, as a bioresource and analyzed the effects of mixotrophic cultivation on its bioresource production efficiency. Internal transcribed spacer (ITS) (ITS1, 5.8S, and ITS2), ribulose bisphosphate carboxylase large subunit (rbcL), and elongation factor Tu (tufa) regions were used for molecular identification and phylogenetic analysis. B. sudetica KNUA107 had a strong relationship with the green algae of Botryococcus and Botryosphaerella genera, which are colony-forming species, and was also associated with members of the Neochloris genus. To improve biomass productivity, we tested mixotrophic cultivation conditions using several organic carbon sources. Glucose supplementation stimulated B. sudetica KNUA107 growth and reduced the time needed to reach the stationary phase. In addition, the colony size was 1.5–2.0 times larger with glucose than in photoautotrophic cultures, and settleability improved in proportion to colony size. The total lipid content and biomass productivity were also higher in cultures supplemented with glucose. Among the lipid components, saturated fatty acids and monounsaturated fatty acids had the highest proportion. Our study suggests that B. sudetica KNUA107, which has enhanced efficiency in biomass production and lipid components under mixotrophic cultivation, has high potential as a bioresource.

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Formation of algal flocs from activated sludge in synthetic medium and secondary treated wastewater

Biliani

Manariotis

2022

J of Chemical Tech & Biotech

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BACKGROUND Photogranules seem to be an alternative solution for wastewater treatment and biomass harvesting. The aim of our work was to investigate the formation of algal flocs as an efficient method for the treatment of wastewater and separation of algal cells. RESULTS The progressive change of activated sludge to algal flocs was evaluated under static and stirring conditions using a synthetic substrate (modified Blue Green‐11 medium) and the secondary effluent from an activated sludge wastewater treatment plant. Algal flocs were observed in all cultures by day 10 and a high chlorophyll concentration was detected in all cases reaching values up to 610–630 μg L−1 at the end of the experiment after 30 days. The size of flocs in all cultures at either static or mixing conditions ranged from 330 to 994 μm, resulting in biomass concentration from 330 to 660 mg L−1. The cultures in secondary effluent at static conditions presented the greatest size, and the mean diameter on days 10 and 30 was 250 and 994 μm, respectively. The cultures were efficient in nutrient removal and, by the end of the experiment, nitrates and phosphates were completely consumed. CONCLUSIONS Algal flocs were developed from activated sludge without adding any other flocculant and a highly efficient biomass was developed, which can easily settle and remove nutrients from the medium. © 2022 Society of Chemical Industry (SCI).

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Microalgae harvesting by fungal-assisted bioflocculation

Cited by 36 publications

References 126 publications

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

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

Enhancement of Biomass Production in Colony-Forming Green Algae, Botryosphaerella sudetica, Under Mixotrophic Cultivation

Formation of algal flocs from activated sludge in synthetic medium and secondary treated wastewater

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