Next Article in Journal
The Lipid Profile of the Endomyces magnusii Yeast upon the Assimilation of the Substrates of Different Types and upon Calorie Restriction
Previous Article in Journal
The Toxicity of Salicylhydroxamic Acid and Its Effect on the Sensitivity of Ustilaginoidea virens to Azoxystrobin and Pyraclostrobin
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
JoF
Volume 8
Issue 11
10.3390/jof8111232
jof-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi

by
Anna Civzele
* and
Linda Mezule
Water Research and Environmental Biotechnology Laboratory, Water Systems and Biotechnology Institute, Faculty of Civil Engineering, Riga Technical University, LV-1048 Riga, Latvia
*
Author to whom correspondence should be addressed.
J. Fungi 2022, 8(11), 1232; https://doi.org/10.3390/jof8111232
Submission received: 21 October 2022 / Revised: 17 November 2022 / Accepted: 17 November 2022 / Published: 21 November 2022
Browse Figures
Versions Notes

Abstract

Tertiary wastewater treatment with microalgae incorporates environmental sustainability with future technologies and high exploitation costs. Despite the apparent ecological benefits of microalgae-assisted wastewater treatment/biomass-based resource production, technological improvements are still essential to compete with other technologies. Bio-flocculation instead of mechanical harvesting has been demonstrated as an alternative cost-effective approach. So far, mostly filamentous fungi of genus Aspergillus have been used for this purpose. Within this study, we demonstrate a novel approach of using white-rot fungi, with especially high potential of algae—Irpex lacteus complex that demonstrates efficiency with various microalgae species at a broad range of temperatures (5–20 °C) and various pH levels. Harvesting of microalgae from primary and secondary wastewater resulted in 73–93% removal efficiencies within the first 24 h and up to 95% after 48 h. The apparent reuse potential of the algae—I. lacteus pellets further complements the reduced operating costs and environmental sustainability of bio-flocculation technology.

Graphical Abstract

1. Introduction

Microalgae cultivation and biomass exploitation has been widely studied, and technology scale-up to an industrial level is well known. Moreover, the potential of microalgae has been also recognized by non-fuel industries, including wastewater treatment [1,2,3,4], where the cultivation of the algae not only produces valuable biomass, but also effectively removes excess nutrients. Introduction of microalgae in wastewater treatment can increase the overall nitrogen and phosphorous removal efficiency from 39 to 66% and from 32 to 89% [5], respectively, thus minimizing the impact of wastewater on the eutrophication of natural waters [6].
Still, one of the major technological bottlenecks in the wide scale application of microalgae for tertiary wastewater treatment is related to biomass harvesting, which can contribute up to 30% of the total production costs, mainly due to the small size of the microalgae cells (5–30 µm) [7] and their colloidal stability in suspension [8]. One of the simplest harvesting approaches is sedimentation which is known for low capital and operating costs, low energy demand and no disruptive effect on the cells. However, it requires high land area [7], leaving no possibility to be introduced into most of the wastewater treatment plants (WWTPs). Alternatively, physical (filtration, gravity sedimentation, flotation and centrifugation), chemical (chemical coagulation and flocculation), biological (bio-flocculation), electrical or a combination of these harvesting methods [9] can be used. Flotation and sedimentation are economically feasible and simple, but they usually require prior chemical coagulation or flocculation [10,11,12]. These technologies in turn can be fast and simple, but toxic to the microalgae and also expensive due to the requirements of chemicals [8]. Electrical methods, on the other hand, do not require the use of chemicals [13], but have high operating costs due to high electricity consumption [14]. Filtration and centrifugation are also characterized by high operational and capital costs, but these methods have high recovery efficiencies [15,16].
In recent years, bio-flocculation using other microorganisms has been offered as a method for microalgae harvesting [9,17,18,19]. The process of microalgae bio-flocculation with filamentous fungi of the genus Aspergillus is the most widely described [20,21,22,23,24,25]. By employing pellet-assisted harvesting, more than 90% removal efficiency of Chlorella vulgaris was achieved after 24 h due to bio-flocculation caused by Aspergillus niger [20]. With Aspergillus fumigatus, the concentration of Scenedesmus quadricauda was reduced by more than 95% in 48 h [21] and Chlorella protothecoides by 80% in 24 h [22]. Integrating spore-assisted harvesting, 93% and more than 95% removal efficiency of Chlorella vulgaris was provided by adding Aspergillus oryzae [23] and A. niger [24], respectively, in 72 h. It was also reported that 98% Botryococcus braunii harvesting efficiency was ensured within 12 h by adding A. fumigatus [25]. Furthermore, when the biomass flocculation occurs, it can be removed with traditional sedimentation, non-reagent flotation or sieving. Given the non-toxicity of this technology in general, the potential cost-effectiveness and the high-harvesting efficiency [9,26], microalgae co-cultivation with filamentous fungi can be considered as a potentially efficient and optimal method of microalgae harvesting. It was also reported that the combination of fungal and algal biomass may cause positive effects on the total biofuel production, and harvested fungi-algae pellets could be considered as value-added feedstock for the production of biofuels, including biodiesel, biomethane, bioethanol and biohydrogen [9]. However, despite the well-demonstrated efficiency of this technology [20,21,22,23,24,25], it is still blanked out by a lack of large-scale testing, relatively long flocculation times and limitations in the reuse of the obtained biomass after wastewater treatment and possible wastewater contamination with Aspergillus spp. spores and its leakage into the environment.
In this study, an alternative microalgae bio-flocculation technology using white-rot and soil fungi was investigated. The potential of using filamentous white-rot fungi such as Irpex lacteus, Trametes versicolor, Pleurotus ostreatus and soil fungi such as Trichoderma reesei has been demonstrated in the degradation of pharmaceutical substances from wastewater [27] and lignocellulosic biomass with high enzymatic activity in the apex of the hyphae [28,29]. Based on these investigations and the observed extensive formation of hyphae, it has been proposed that these fungi may be suitable candidates for microalgae harvesting from wastewater and subsequent lignocellulose-degrading enzyme production to improve the hydrolysis process of cellulosic materials that are essential for bioethanol production [30]. Moreover, considering the lower risk of the aforementioned fungi affecting human health compared to Aspergillus spp. [31,32,33], the use of white-rot fungi could become a safe alternative to pathogenic fungal species in the microalgae removal process. Furthermore, these experimental studies have suggested the most suitable cultivation and handling conditions and demonstrate the reuse of the material during the harvesting process, thus, limiting the amount of process waste.

2. Materials and Methods

2.1. Microorganisms and Culture Conditions

Tetradesmus obliquus (CCAP 276/10), Desmodesmus communis (CCAP 276/4B) and Chlorella vulgaris (CCAP 211/11B) were used as representative microalgae within this study. For harvesting, microalgae suspension was prepared by culturing the microalgae in 1000 mL Pyrex® bottles in BG-11 growth medium for 10 days at 20–27 °C. Continuous 10 Lh−1 aeration and the blue-red spectrum fluorescent light (180 μmol m2 s−1 at a 16:8 h lighting regime) was provided during microalgae cultivation. Microalgae cells for microalgae harvesting tests were obtained during the exponential phase.
White-rot fungi Irpex lacteus (Fr.) Fr., Pleurotus dryinus (Pers.) P. Kumm, Pleurotus ostreatus (DSM 1020), Trametes versicolor (DSM 6401), Pycnoporus cinnabarinus (Fr.) P. Karst and soil fungus Trichoderma reesei (DSM 768) were maintained on potato dextrose agar (Oxoid Ltd., Basingstoke, Hants, UK) at 2–8 °C. Each fungal species was inoculated into 250 mL Erlenmeyer flasks in a culture medium containing 0.8 g KH2PO4, 0.4 g K2HPO4, 0.5 g MgSO4·7H2O, 2 g NH4NO3, 2 g yeast extract and 10 g glucose per L and then cultivated for 3 days in an orbital shaker (New Brunswick™ Innova® 43, Eppendorf Austria GmbH, Wien, Austria) at 150 rpm and 30 °C. The pH level in the medium was adjusted to 5.3–5.5.

2.2. Wastewater Source

Primary and secondary effluents were collected at a biological wastewater treatment plant “Daugavgriva” (Riga, Latvia, PE > 100 000) after primary settlers and after biochemical oxidation and secondary settlers. Prior to use, the wastewater was filtered through a 0.45 µm cellulose-acetate filter to remove indigenous bacteria and microparticles. The concentrations of all quality parameters for both types of wastewater (Table 1) were provided using internal WWTP monitoring performed according to standard methodology [34,35,36,37,38,39,40,41].

2.3. Experimental Setup

Pre-cultured fungal pellets were mixed with a heat-pretreated microalgae culture with a concentration of 5 × 106 cell/mL in Schott Duran 100 mL laboratory bottles, which were then placed on an orbital shaker (PSU-20i, Biosan, Riga, Latvia) at 150 rpm 20 °C. In lower temperature test experiments, the shaker was inserted into a cooling incubator. The microalgal biomass was heat-pretreated by boiling (5 min at 1 atm) to eliminate the risk of microbial contamination and to ensure controlled conditions except for the harvesting tests performed in wastewater. Microalgae harvesting tests were performed with a fungi:algae mass ratio of 1:2. During each experiment, the concentration of microalgae was measured daily in three repeats to determine the progress of microalgae harvesting. Each parameter was assessed in three independent replicates.

2.4. Experimental Harvesting Conditions

First, to identify the fungal species with the most efficient algal recovery capacity, I. lacteus, P. dryinus, P. ostreatus, T. versicolor, P. cinnabarinus and T. reesei were individually added to either T. obliquus, D. communis or C. vulgaris suspensions under the conditions described above.
Secondly, fresh pre-cultured fungal pellets and reused algal-fungal pellets were again added to the respective fresh suspensions of T. obliquus, D. communis and C. vulgaris to determine and compare the efficiency of use of pre-cultured and recycled pellets.
Thirdly, to determine the impact of the bio-flocculation conditions, pH and temperature on the bio-flocculation process, a series of tests were run at a pH from 4 to 9 and at 5, 10, 15 and 20 °C with the same conditions as used previously. For these experiments, only the most efficient fungal species were used.
Lastly, to evaluate the efficiency of the studied microalgae harvesting method under real conditions, primary and secondary wastewater was used as harvesting mediums.

2.5. Microalgal Cell Measurements

To determine the reduction in microalgae concentration during the bio-flocculation process, microalgae cell concentration was measured using a UV-visible spectrophotometer (GENESYS 150, Thermo Fisher Scientific Inc., Waltham, MA, USA) at 680 nm absorbance wavelength which is proportional to the change of cell numbers in most unicellular organisms [42]. Microalgae cell concentration in these samples was calculated by measuring the absorption using a UV-visible spectrophotometer in a linear interval. The percentage reduction in the number of microalgae cells in the fluid and, in turn, the harvesting efficiency was calculated using Equation (1):
E % = C 0 −   C C 0 × 100 %
where E% is the microalgae harvesting efficiency, C0 (cell/mL) is the initial microalgae concentration before co-cultivation and C (cell/mL) is the final microalgae concentration in suspension.
Individual calibration curves were constructed for each microalgae strain to relate optical density with the microalgae concentration. Each experiment was performed in three repetitions.
To verify the results obtained with the spectrophotometric method, selected samples of known volume were filtered through a 25 mm diameter 0.2 μm pore–size filter (polycarbonate track-etch membrane, Sartorius, Germany) and stained with 10 μg mL−1 DAPI (4′,6-diamidino- 2-phenylindole, Merck, Germany) for 5–10 min according to a protocol described by Denisova et al. (2022) [43]. Cell concentrations were determined with epifluorescence microscopy (Ex: 340/380; Em: > 425, dichromatic mirror 565 nm, Leica DM6000B, Leica Microsystems, Wetzlar, Germany) by counting 20 random fields of view.

2.6. Statistical Analysis

Microsoft Excel 2016 t-test and ANOVA single-parameter tool (significance level ≤ 0.05) were used for data statistical analysis.

3. Results & Discussion

3.1. Microalgae Harvesting with Various Fungal Species

Application of white-rot fungi has been recognized in biomass pretreatment, biochemical and enzyme production, biofuel production and bioremediation [44,45,46,47,48,49,50]. Within this study, Irpex lacteus, Pleurotus dryinus, Pleurotus ostreatus, Trametes versicolor, Pycnoporus cinnabarinus and soil fungus Trichoderma reesei were selected as the representative species. First, the highest efficiency of microalgal cell reduction after the addition of fungi was determined. From these, I. lacteus provided an average of 98.53 ± 0.36% reduction in microalgae cells after 24 h of harvesting and an average of 99.95 ± 0.05% after 72 h. Further, good harvesting results were obtained with P. ostreatus—an average microalgae reduction of 67% was achieved after 24 h, and more than 90% after 48 h. Similar results were obtained after 48 h using P. dryinus and T. versicolor (85.96 ± 5.74% and 90.53 ± 2.57%, respectively). However, comparing to I. lacteus, the efficiency of reduction after 24 h for these fungal species was significantly lower (p < 0.05)—47.72 ± 7.22% and 40.54 ± 4.60%, respectively. Bio-flocculation induced by T. reesei provided more than 80% microalgae removal efficiency, but after 72 h, an increase in turbidity of the suspension was observed due to active fungal growth.
The only fungal species that did not demonstrate any significant results was P. cinnabarinus. The maximum microalgae removal efficiency (38.56 + 9.97%) was obtained after 48 h, following an increase in the turbidity and chromaticity of the suspension. This could be explained by the fact that under certain conditions, P. cinnabarinus produces red-to-orange pigmentation due to phenoxazinone pigments, including cinnabarin, tramesanguin and cinnabarinic acid that can be further released in the environment [51].
The obtained results demonstrate that by using white-rot basidiomycetes, in general, more significant bio-flocculation results can be achieved than with Aspergillus spp. that typically provide more than 95% after 48 h or longer [21,23,52,53]. Furthermore, I. lacteus proved to be the most efficient white-rot fungus for microalgae harvesting (Figure 1) since it showed the most rapid decrease in the suspended microalgae and no algae desorption within 48 h. This could be explained by the fact that I. lacteus pellets have more pronounced mycelial filaments compared to other studied fungal species (Figure 2 and Supplementary Materials Figure S1), which potentially increase the surface area of the hyphae and improve sticking.
Further, I. lacteus performance was validated with other microalgae, C. vulgaris and D. communis, since all these species have been applied in tertiary wastewater treatment and demonstrated a high efficiency of phosphorous and nitrogen removal [42,54,55,56,57]. It was reported that D. communis is able to ensure 94–100% phosphorous removal [56], and by using C. vulgaris, up to 99.8% nitrate and 99.7% phosphate removal can be achieved [54].
In general, more than 90% reduction in all microalgae cells was achieved during the whole treatment time (Figure 3) of 96 h. Twenty-four-h analysis showed a lower reduction efficiency (67.79 ± 2.26%) for C. vulgaris. Nevertheless, after 96 h, 96.13 ± 0.90% of C. vulgaris was removed. At the same time, it took less than 24 h to harvest up to more than 95% of T. obliquus (98.35 ± 0.52%) and 48 h to remove D. communis (95.80 ± 4.50%) (Figure 3). The discrepancies in the removal efficiency could be explained by microalgae cell shape differences; however, when taking this into account during the coupling of microalgae assisted tertiary wastewater treatment with I. lacteus bio-flocculation technology, the risks of inefficient harvesting can be minimized.

3.2. Effect of the Reuse of Algal-Fungal Pellets

Bio-flocculation caused by filamentous fungi can be considered as a potentially environmentally friendly microalgae harvesting technology due to the fact that no addition of toxic chemical coagulants or other chemicals, which are required when using coagulation/flocculation and sedimentation methods, is necessary [14,58]. Thus, by reducing the need of using chemicals in microalgae harvesting, the risk of secondary pollution of wastewater can be reduced. In the case of the studied technology, natural white-rot fungi are used instead of chemicals to induce flocculation of microalgae and to simplify the separation of microalgae cells from the treated wastewater.
It is also essential that the proposed microalgae harvesting technology simultaneously offers the reuse of the harvesting matrix, e.g., algal-fungal pellets in this case. The reuse of fungal pellets can potentially reduce the amount of sludge produced using microalgae harvesting. Thus, the efficiency of using fresh pre-cultured and reused algal-fungal pellets was determined and compared (Figure 4).
As expected, the efficiency of the studied microalgae harvesting method was slightly lower (p > 0.05) when used algal-fungal pellets were introduced in the harvesting (Figure 4). Nevertheless, in all cases, the reduction in microalgae cells followed the same pattern and more than 70% after 48 h reduction and more than 80% after 72 h reduction was observed. After 96 h, a reduction of 93.5% (C. vulgaris) to 99.95% (T. obliquus) was achieved for all three microalgae (Figure 4). Interestingly, a significantly lower harvesting efficiency (p < 0.05) of recycled pellets was achieved only after 24 h of C. vulgaris bio-flocculation, with an average of 36.86% microalgae reduction (Figure 4). However, despite this fact, the reduction in C. vulgaris microalgae after 48 h and longer was practically identical in both cases. In general, a similar trend in the reduction in microalgae concentrations was observed with both pre-cultured and reused pellets.

3.3. Impact of Bio-Flocculation Conditions

In order to test the suitability of the investigated technology under practical field conditions, the efficiency of the method was tested at various pH levels and temperatures characteristic for temperate climate zones. Given the role of the pH in the growth of fungi and that changes in pH can affect the surface properties of fungi and the formation of pellets [23], the effect of pH on the bio-flocculation process was investigated and evaluated. It was hypothesized that at a lower pH, bio-flocculation with fungi will be more efficient since acidic conditions are more suitable for fungal growth than microalgae [9]. Furthermore, as the pH of a wastewater can vary, it was necessary to evaluate the impact of this factor on the bio-flocculation process.
Here, microalgae co-cultivation with I. lacteus was performed at pH 4–9. The highest harvesting rate and efficiency was achieved in the medium with pH 7 (Figure 5). Under neutral conditions, about 99% of the microalgae was harvested within the first 24 h. More than 90% reduction in microalgae was achieved after 48 h at pH 4–6 and after 72 h at a pH above 7. The lowest rate of microalgae removal was observed during bio-flocculation of microalgae at pH 9. This can be explained by the fact that at high pH, net negative charges on microalgae cell walls cause electrostatic repulsion between algal cells, which interferes with the flocculation process [9]. It can be concluded that in the wastewater with a pH around 7, the bio-flocculation process will be most efficient, whereas at a higher or lower pH, it would take longer to ensure the equally high removal of microalgae.
It was determined that the optimal pH conditions for I. lacteus pellets to harvest T. obliquus cells was pH 7. Samples collected from the medium with pH 9 showed the lowest efficiency after 24 h (an average of 62.86 ± 4.08%). However, in general, all results of the T. obliquus harvesting experiments with pH 4.0–9.0 have shown high efficiencies after 72 h—from 94.9 to 99.9% reduction in microalgae cells (Figure 5), so, no significant reduction in the efficiency (p > 0.05) of the technology was observed as a result of the changes in pH. Thus, the technology showed no need for the pH control of the wastewater before microalgae harvesting.
To test the possible effect of temperature on the harvesting efficiency, in addition to room temperature incubation, the bio-flocculation process was provided at 5, 10 and 15 °C. In general, after 24 h of incubation, no significant difference (p > 0.05) in bio-flocculation efficiency was observed, indicating no effect of temperature on the process. After 48 h, the change in bio-flocculation efficiency was even less significant, with a reduction of 94.84 + 5.16% microalgae concentration at 15 °C, 92.04 + 0.67% at 10 °C and 91.70 + 1.61% at 5 °C. A minor decrease in harvesting efficiency at the initial stage of 5 °C regime was observed; however, prolonged bio-flocculation yielded comparable results under all temperature regimes (Figure 6). Thus, the studied harvesting method is effective even at low temperatures, and after 24 h, 77–93% of microalgae cells are recovered from the liquid.

3.4. Algal-Fungal Co-Cultivation in Wastewater

D. communis, T. obliquus and C. vulgaris suspensions and I. lacteus pellets were used in this experiment to test the efficiency of the studied microalgae harvesting method in real wastewater. On average, the concentration of T. obliquus was reduced by 82.02 ± 3.05% in the primary wastewater and by 77.19 ± 3.13% in the secondary wastewater after 24 h. D. communis was reduced by 73.35 ± 1.10% and 93.22 ± 2.56% in the primary and secondary wastewater, respectively, after 24 h. After the same time, the concentration of C. vulgaris was reduced by 76.12 ± 6.47% in the primary wastewater and by 77.55 ± 5.78% in the secondary wastewater. More than 95% of the D. communis microalgae cells were recovered from both wastewater types after 48 h. T. obliquus concentration was reduced by more than 90% after 72 h and C. vulgaris after 96 h in both wastewater types (Figure 7).
Till now, bio-flocculation of microalgae has been typically associated with the use of filamentous fungi from genus Aspergillus [20,21,22,23,24,25]. Within this study, we have used an alternative approach of replacing Aspergillus with white-rot fungi that have demonstrated their potential in many other biotechnological fields. An especially high effect of bio-flocculation was observed with I. lacteus, which is known for its biodegradation ability of dyes, lignocellulose and enzyme production, but has not been previously used for microalgae bio-flocculation from wastewater. Despite the fact that the process efficiency depended on the harvested microalgae species, pH level, temperature and bio-flocculation medium, efficiencies of > 99% can be achieved even with reused pellets in a reasonably short time. Thus, I. lacteus can become a good and safe alternative to Aspergillus spp. in microalgae bio-flocculation due to its relatively high microalgae-harvesting efficiency and lower risk of negative effects on human health, given that the majority of Aspergillus can be pathogenic [31,32,33]. The lack of processed chemicals and their subsequent removal, recirculation of the fungal pellets and potential further use of the pellets are only some of the positive features of algal—I. lacteus complex that allow reduced technological operating costs and environmental sustainability.

4. Conclusions

This study confirmed the highly efficient bio-flocculation capacity of Irpex lacteus which can provide more than 95% reduction in Tetradesmus obliquus and approximately 70% reduction in Desmodesmus communis and Chlorella vulgaris within 24 h of bio-flocculation at a temperature range from 5–20 °C. In primary and secondary wastewater, 73% to 93% removal efficiency was obtained. Furthermore, I. lacteus pellets can be reused for further microalgae harvesting.
Given that no chemicals were needed to induce the flocculation process, the proposed microalgae harvesting method is environmentally friendly, as well as safer for human health and the environment when compared to the use of natural or genetically improved Aspergillus spp.
The algal-fungal pellets formed during the bio-flocculation process are characterized by a rather large size (about 5–10 mm) and a high durability. These factors potentially facilitate the removal of microalgae after flocculation, which in turn can also reduce the capital and operational costs of the microalgae harvesting stage. Therefore, the studied technology can potentially become a cost-effective solution for microalgae harvesting. At the same time, the algal-fungal biomass obtained as a result of bio-flocculation could be considered as potential feedstock for the biofuel production. However, further research is needed to identify the effect of white-rot fungi on the harvested biomass composition.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/jof8111232/s1, Figure S1: Microalgae harvesting after tertiary wastewater treatment with white-rot fungi

Author Contributions

Conceptualization, A.C. and L.M.; methodology, A.C. and L.M.; formal analysis, A.C.; investigation, A.C.; writing—original draft preparation, A.C and L.M.; writing—review and editing, L.M. All authors have read and agreed to the published version of the manuscript.

Funding

The research was financially supported by the Latvian Council of Science, project “Post-treatment of municipal wastewater using sequenced-batch photobioreactor technology” (Project No. LZP-2019/1-0271).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Borowitzka, M.A. High-value products from microalgae—Their development and commercialisation. J. Appl. Phycol. 2013, 25, 743–756. [Google Scholar] [CrossRef]
  2. Aliyu, A.; Lee, J.G.M.; Harvey, A.P. Microalgae for biofuels: A review of thermochemical conversion processes and associated opportunities and challenges. Bioresour. Technol. Rep. 2021, 15, 100694. [Google Scholar] [CrossRef]
  3. Ali, S.; Paul Peter, A.; Chew, K.W.; Munawaroh, H.; Show, P.L. Resource recovery from industrial effluents through the cultivation of microalgae: A review. Bioresour. Technol. 2021, 337, 125461. [Google Scholar] [CrossRef] [PubMed]
  4. Mohsenpour, S.F.; Hennige, S.; Willoughby, N.; Adeloye, A.; Gutierrez, T. Integrating micro-algae into wastewater treatment: A review. Sci. Total Environ. 2021, 752, 142168. [Google Scholar] [CrossRef] [PubMed]
  5. Tang, C.C.; Tian, Y.; Liang, H.; Zuo, W.; Wang, Z.W.; Zhang, J.; He, Z.W. Enhanced nitrogen and phosphorus removal from domestic wastewater via algae-assisted sequencing batch biofilm reactor. Bioresour. Technol. 2018, 250, 185–190. [Google Scholar] [CrossRef] [PubMed]
  6. Rout, P.R.; Shahid, M.K.; Dash, R.R.; Bhunia, P.; Liu, D.; Varjani, S.; Zhang, T.C.; Surampalli, R.Y. Nutrient removal from domestic wastewater: A comprehensive review on conventional and advanced technologies. J. Environ. Manag. 2021, 296, 113246. [Google Scholar] [CrossRef]
  7. Tiwari, A.; Kiran, T.; Pandey, A. Chapter 14-Algal cultivation for biofuel production. In Second and Third Generation of Feedstocks; Basile, A., Dalena, F., Eds.; Elsevier: Amsterdam, The Netherlands, 2019; pp. 383–403. [Google Scholar] [CrossRef]
  8. Vandamme, D.; Foubert, I.; Muylaert, K. Flocculation as a low-cost method for harvesting microalgae for bulk biomass production. Trends Biotechnol. 2013, 31, 233–239. [Google Scholar] [CrossRef]
  9. Chu, R.; Li, S.; Zhu, L.; Yin, Z.; Hu, D.; Liu, C.; Mo, F. A review on co-cultivation of microalgae with filamentous fungi: Efficient harvesting, wastewater treatment and biofuel production. Renew. Sustain. Energy Rev. 2021, 139, 110689. [Google Scholar] [CrossRef]
  10. Smith, B.; Davis, R. Sedimentation of algae flocculated using naturally-available, magnesium-based flocculants. Algal Res. 2012, 1, 32–39. [Google Scholar] [CrossRef]
  11. Papazi, A.; Makridis, P.; Divanach, P. Harvesting Chlorella minutissima using cell coagulants. J. Appl. Phycol. 2010, 22, 349–355. [Google Scholar] [CrossRef]
  12. Rubio, J.; Souza, M.L.; Smith, R.W. Overview of flotation as a wastewater treatment technique. Miner. Eng. 2002, 15, 139–155. [Google Scholar] [CrossRef]
  13. Uduman, N.; Qi, Y.; Danquah, M.K.; Forde, G.M.; Hoadley, A. Dewatering of microalgal cultures: A major bottleneck to algae-based fuels. J. Renew. Sustain. Energy 2010, 2, 012701. [Google Scholar] [CrossRef]
  14. Barros, A.; Gonçalves, A.L.; Simões, M.; Pires, J.C. Harvesting techniques applied to microalgae: A review. Renew. Sustain. Energy Rev. 2015, 41, 1489–1500. [Google Scholar] [CrossRef]
  15. Najjar, Y.S.H.; Abu-Shamleh, A. Harvesting of microalgae by centrifugation for biodiesel production: A review. Algal Res. 2020, 51, 02046. [Google Scholar] [CrossRef]
  16. Zhang, X.; Hu, Q.; Sommerfeld, M.; Puruhito, E.; Chen, Y. Harvesting algal biomass for biofuels using ultrafiltration membranes. Bioresour. Technol. 2010, 101, 5297–5304. [Google Scholar] [CrossRef] [PubMed]
  17. Ummalyma, S.B.; Gnansounou, E.; Sukumaran, R.K.; Sindhu, R.; Pandey, A.; Sahoo, D. Bioflocculation: An alternative strategy for harvesting of microalgae-An overview. Bioresour. Technol. 2017, 242, 227–235. [Google Scholar] [CrossRef]
  18. Zhao, Y.; Guo, G.; Sun, S.; Hu, C.; Liu, J. Co-pelletization of microalgae and fungi for efficient nutrient purification and biogas upgrading. Bioresour. Technol. 2019, 289, 121656. [Google Scholar] [CrossRef] [PubMed]
  19. Zhang, J.; Hu, B. A novel method to harvest microalgae via co-culture of filamentous fungi to form cell pellets. Bioresour. Technol. 2012, 114, 529–535. [Google Scholar] [CrossRef]
  20. Li, Y.; Xu, Y.; Liu, L.; Li, P.; Yan, Y.; Chen, T.; Zheng, T.; Wang, H. Flocculation mechanism of Aspergillus niger on harvesting of Chlorella vulgaris biomass. Algal Res. 2017, 25, 402–412. [Google Scholar] [CrossRef]
  21. Wrede, D.; Taha, M.; Miranda, A.F.; Kadali, K.; Stevenson, T.; Ball, A.S.; Mouradov, A. Co-cultivation of fungal and microalgal cells as an efficient system for harvesting microalgal cells, lipid production and wastewater treatment. PLoS ONE 2014, 9, e113497. [Google Scholar] [CrossRef]
  22. Muradov, N.; Taha, M.; Miranda, A.F.; Wrede, D.; Kadali, K.; Gujar, A.; Stevenson, T.; Ball, A.S.; Mouradov, A. Fungal-assisted algal flocculation: Application in wastewater treatment and biofuel production. Biotechnol. Biofuels 2015, 8, 24. [Google Scholar] [CrossRef] [PubMed]
  23. Zhou, W.; Min, M.; Hu, B.; Ma, X.; Liu, Y.; Wang, Q.; Shi, J.; Chen, P.; Ruan, R. Filamentous fungi assisted bio-flocculation: A novel alternative technique for harvesting heterotrophic and autotrophic microalgal cells. Sep. Purif. Technol. 2013, 107, 158–165. [Google Scholar] [CrossRef]
  24. Alrubaie, G.; Al-Shammari, R.H.H. Microalgae Chlorella Vulgaris Harvesting Via Co-Pelletization with Filamentous Fungus. Baghdad Sci. J. 2018, 15, 31–36. [Google Scholar] [CrossRef]
  25. Al-Hothaly, K.A.; Adetutu, E.M.; Taha, M.; Fabbri, D.; Lorenzetti, C.; Conti, R.; May, B.H.; Shar, S.S.; Bayoumi, R.A.; Ball, A.S. Bio-harvesting and pyrolysis of the microalgae Botryococcus braunii. Bioresour. Technol. 2015, 191, 117–123. [Google Scholar] [CrossRef] [PubMed]
  26. Leng, L.; Li, W.; Chen, J.; Leng, S.; Chen, J.; Wei, L.; Peng, H.; Li, J.; Zhou, W.; Huang, H. Co-culture of fungi-microalgae consortium for wastewater treatment: A review. Bioresour. Technol. 2021, 330, 125008. [Google Scholar] [CrossRef] [PubMed]
  27. Dalecka, B.; Juhna, T.; Rajarao, G.K. Constructive use of filamentous fungi to remove pharmaceutical substances from wastewater. J. Water Process Eng. 2020, 33, 100992. [Google Scholar] [CrossRef]
  28. Mezule, L.; Civzele, A. Bioprospecting White-Rot Basidiomycete Irpex lacteus for Improved Extraction of Lignocellulose-Degrading Enzymes and Their Further Application. J. Fungi 2020, 6, 256. [Google Scholar] [CrossRef]
  29. Mezule, L.; Berzina, I.; Strods, M. The Impact of Substrate–Enzyme Proportion for Efficient Hydrolysis of Hay. Energies 2019, 12, 3526. [Google Scholar] [CrossRef]
  30. Laezza, C.; Salbitani, G.; Carfagna, S. Fungal Contamination in Microalgal Cultivation: Biological and Biotechnological Aspects of Fungi-Microalgae Interaction. J. Fungi 2022, 8, 1099. [Google Scholar] [CrossRef]
  31. Dagenais, T.R.; Keller, N.P. Pathogenesis of Aspergillus fumigatus in Invasive Aspergillosis. Clin. Microbiol. Rev. 2009, 22, 447–465. [Google Scholar] [CrossRef]
  32. Paulussen, C.; Hallsworth, J.E.; Álvarez-Pérez, S.; Nierman, W.C.; Hamill, P.G.; Blain, D.; Rediers, H.; Lievens, B. Ecology of aspergillosis: Insights into the pathogenic potency of Aspergillus fumigatus and some other Aspergillus species. Microb. Biotechnol. 2017, 10, 296–322. [Google Scholar] [CrossRef] [PubMed]
  33. Morgan, J.; Wannemuehler, K.A.; Marr, K.A.; Hadley, S.; Kontoyiannis, D.P.; Walsh, T.J.; Fridkin, S.K.; Pappas, P.G.; Warnock, D.W. Incidence of invasive aspergillosis following hematopoietic stem cell and solid organ transplantation: Interim results of a prospective multicenter surveillance program. Med. Mycol. 2005, 43 (Suppl. 1), S49–S58. [Google Scholar] [CrossRef] [PubMed]
  34. ISO 5815-1:2019; Water Quality—Determination of Biochemical Oxygen Demand after n Days (BODn)—Part 1: Dilution and Seeding Method with Allylthiourea Addition. International Organization for Standardization: Geneva, Switzerland, 2019. Available online: https://www.iso.org/standard/69058.html (accessed on 2 November 2022).
  35. ISO 6060:1989; Water Quality—Determination of the Chemical Oxygen Demand. International Organization for Standardization: Geneva, Switzerland, 1989. Available online: https://www.iso.org/standard/12260.html (accessed on 2 November 2022).
  36. BS EN 872:2005; Water Quality. Determination of Suspended Solids. Method by Filtration through Glass Fibre Filters. European Standards: Pilsen, Czech Republic, 2005. Available online: https://www.en-standard.eu/bs-en-872-2005-water-quality-determination-of-suspended-solids-method-by-filtration-through-glass-fibre-filters/ (accessed on 2 November 2022).
  37. ISO 7150-1:1984; Water Quality—Determination of Ammonium—Part 1: Manual Spectrometric Method. International Organization for Standardization: Geneva, Switzerland, 1984. Available online: https://www.iso.org/standard/13742.html (accessed on 2 November 2022).
  38. ISO 6777:1984; Water Quality—Water Quality—Determination of Nitrite—Molecular Absorption Spectrometric Method. International Organization for Standardization: Geneva, Switzerland, 1984. Available online: https://www.iso.org/standard/13273.html (accessed on 2 November 2022).
  39. ISO 7890-3:1988; Water Quality—Determination of Nitrate—Part 3: Spectrometric Method Using Sulfosalicylic Acid. International Organization for Standardization: Geneva, Switzerland, 1988. Available online: https://www.iso.org/standard/14842.html (accessed on 2 November 2022).
  40. ISO 6878:2004; Water Quality—Determination of Phosphorus—Ammonium Molybdate Spectrometric Method. International Organization for Standardization: Geneva, Switzerland, 2004. Available online: https://www.iso.org/standard/36917.html (accessed on 2 November 2022).
  41. ISO 0523:2008; Water Quality—Determination of pH. International Organization for Standardization: Geneva, Switzerland, 2008. Available online: https://www.iso.org/standard/51994.html (accessed on 2 November 2022).
  42. Lavrinovičs, A.; Mežule, L.; Juhna, T. Microalgae starvation for enhanced phosphorus uptake from municipal wastewater. Algal Res. 2020, 52. [Google Scholar] [CrossRef]
  43. Denisova, V.; Mezule, L.; Juhna, T. The effect of chitosan nanoparticles on Escherichia coli viability in drinking water disinfection. Water Pract. Technol. 2022, 17, 537–543. [Google Scholar] [CrossRef]
  44. Abdel-Hamid, A.M.; Solbiati, J.O.; Cann, I.K. Insights into lignin degradation and its potential industrial applications. Adv. Appl. Microbiol. 2013, 82, 1–28. [Google Scholar] [CrossRef]
  45. Saraswat, P.; Yadav, K.; Gupta, A.; Prasad, M.; Ranjan, R. Chapter 34-Physiological and molecular basis for remediation of polyaromatic hydrocarbons. In Handbook of Bioremediation; Hasanuzzaman, M., Prasad, M.N.V., Eds.; Academic Press: Cambridge, MA, USA, 2021; pp. 535–550. [Google Scholar] [CrossRef]
  46. Kalinoski, R.M. White-Rot Fungi as Pretreatment Agents for Wood Destined for Biofuel Applications. Masters Theses, Eastern Illinois University, Charleston, IL, USA, 2016; p. 2450. [Google Scholar]
  47. Canam, T.; Dumonceaux, T.J.; Record, E.; Li, Y. White-rot fungi: The key to sustainable biofuel production? Biofuels 2013, 4, 247–250. [Google Scholar] [CrossRef]
  48. Jurado, M.; Martinèz, À.T.; Martinez, M.J.; Saparrat, M.C.N. 6.45-Application of White-Rot Fungi in Transformation, Detoxification, or Revalorization of Agriculture Wastes: Role of Laccase in the Processes. In Comprehensive Biotechnology, 2nd ed.; Moo-Young, M., Ed.; Academic Press: Cambridge, MA, USA, 2011; pp. 595–603. [Google Scholar] [CrossRef]
  49. He, K.; Chen, G.; Zeng, G.; Huang, Z.; Guo, Z.; Huang, T.; Peng, M.; Shi, J.; Hu, L. Applications of white rot fungi in bioremediation with nanoparticles and biosynthesis of metallic nanoparticles. Appl. Microbiol. Biotechnol. 2017, 101, 4853–4862. [Google Scholar] [CrossRef]
  50. Zhuo, R.; Fan, F. A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants. Sci. Total Environ. 2021, 778, 146132. [Google Scholar] [CrossRef]
  51. Göçenoğlu, A.; Pazarlioglu, N. Cinnabarinic acid: Enhanced production from Pycnoporus cinnabarinus, characterization, structural and functional properties. Hacet. J. Biol. Chem. 2014, 42, 281–290. [Google Scholar] [CrossRef]
  52. Nasir, N.M.; Bakar, N.S.; Lananan, F.; Abdul Hamid, S.H.; Lam, S.S.; Jusoh, A. Treatment of African catfish, Clarias gariepinus wastewater utilizing phytoremediation of microalgae, Chlorella sp. with Aspergillus niger bio-harvesting. Bioresour. Technol. 2015, 190, 492–498. [Google Scholar] [CrossRef]
  53. Oliveira, H.R.; Bassin, I.D.; Cammarota, M.C. Bioflocculation of cyanobacteria with pellets of Aspergillus niger: Effects of carbon supplementation, pellet diameter, and other factors in biomass densification. Bioresour. Technol. 2019, 294, 122167. [Google Scholar] [CrossRef] [PubMed]
  54. Tejido-Nuñez, Y.; Aymerich, E.; Sancho, L.; Refardt, D. Treatment of aquaculture effluent with Chlorella vulgaris and Tetradesmus obliquus: The effect of pretreatment on microalgae growth and nutrient removal efficiency. Ecol. Eng. 2019, 136, 1–9. [Google Scholar] [CrossRef]
  55. Rugnini, L.; Ellwood, N.; Costa, G.; Falsetti, A.; Congestri, R.; Bruno, L. Scaling-up of wastewater bioremediation by Tetradesmus obliquus, sequential bio-treatments of nutrients and metals. Ecotoxicol. Environ. Saf. 2019, 172, 59–64. [Google Scholar] [CrossRef] [PubMed]
  56. Rugnini, L.; Costa, G.; Congestri, R.; Antonaroli, S.; Sanità di Toppi, L.; Bruno, L. Phosphorus and metal removal combined with lipid production by the green microalga Desmodesmus sp.: An integrated approach. Plant Physiol. Biochem. 2018, 125, 45–51. [Google Scholar] [CrossRef]
  57. Kong, W.; Kong, J.; Ma, J.; Lyu, H.; Feng, S.; Wang, Z.; Yuan, P.; Shen, B. Chlorella vulgaris cultivation in simulated wastewater for the biomass production, nutrients removal and CO2 fixation simultaneously. J. Environ. Manag. 2021, 284, 112070. [Google Scholar] [CrossRef]
  58. Al hattab, M.; Ghaly, A.; Hammouda, A. Microalgae Harvesting Methods for Industrial Production of Biodiesel: Critical Review and Comparative Analysis. J. Fundam Renew. Energy Appl. 2015, 5, 154. [Google Scholar] [CrossRef]
Jof 08 01232 g001
Figure 1. Percentage of suspended T. obliquus when selected fungal species were used for bio-flocculation. Standard deviation represents the average from three replicates.
Figure 1. Percentage of suspended T. obliquus when selected fungal species were used for bio-flocculation. Standard deviation represents the average from three replicates.
Jof 08 01232 g001
Jof 08 01232 g002
Figure 2. (a) T. obliquus suspension before bio-flocculation; (b) I. lacteus culture in liquid medium before adding to the T. obliquus suspension; (c) algal-fungal pellets formed in T. obliquus—I. lacteus complex after 24 h.
Figure 2. (a) T. obliquus suspension before bio-flocculation; (b) I. lacteus culture in liquid medium before adding to the T. obliquus suspension; (c) algal-fungal pellets formed in T. obliquus—I. lacteus complex after 24 h.
Jof 08 01232 g002
Jof 08 01232 g003
Figure 3. Percentage of selected microalgae remaining in suspension when bio-flocculated with I. lacteus against the treatment time. Standard deviation represents the average from three replicates.
Figure 3. Percentage of selected microalgae remaining in suspension when bio-flocculated with I. lacteus against the treatment time. Standard deviation represents the average from three replicates.
Jof 08 01232 g003
Jof 08 01232 g004
Figure 4. Percentage of selected microalgae remaining in the suspension when pre-cultured I. lacteus and recycled algal—I. lacteus pellets are used for respective microalgae bio-flocculation. Standard deviation represents the average from three replicates.
Figure 4. Percentage of selected microalgae remaining in the suspension when pre-cultured I. lacteus and recycled algal—I. lacteus pellets are used for respective microalgae bio-flocculation. Standard deviation represents the average from three replicates.
Jof 08 01232 g004
Jof 08 01232 g005
Figure 5. T. obliquus harvesting efficiency at pH levels: (a) 4; (b) 5; (c) 6; (d) 7; (e) 8; (f) 9 with I. lacteus pellets. Standard deviation represents the average from three replicates.
Figure 5. T. obliquus harvesting efficiency at pH levels: (a) 4; (b) 5; (c) 6; (d) 7; (e) 8; (f) 9 with I. lacteus pellets. Standard deviation represents the average from three replicates.
Jof 08 01232 g005
Jof 08 01232 g006
Figure 6. T. obliquus harvesting efficiency at 5, 10, 15 and 20 °C with I. lacteus pellets. Standard deviation represents the average from three replicates.
Figure 6. T. obliquus harvesting efficiency at 5, 10, 15 and 20 °C with I. lacteus pellets. Standard deviation represents the average from three replicates.
Jof 08 01232 g006
Jof 08 01232 g007
Figure 7. Percentage of D. communis, T. obliquus and C. vulgaris in primary and secondary wastewater after bio-flocculation with I. lacteus. Standard deviation represents the average from three replicates.
Figure 7. Percentage of D. communis, T. obliquus and C. vulgaris in primary and secondary wastewater after bio-flocculation with I. lacteus. Standard deviation represents the average from three replicates.
Jof 08 01232 g007
Table 1. Parameters of primary and secondary wastewater used for the experiments.
Table 1. Parameters of primary and secondary wastewater used for the experiments.
ParameterMethodPrimary WastewaterSecondary Wastewater
BOD5 (biochemical oxygen demand)ISO 5815-1 1606mg/L
COD (chemical oxygen demand)ISO 6060 48039mg/L
SS (suspended solids)EN 872 2106mg/L
NH4-N (dissolved ammonium)ISO 7150-1 452.02mg/L
NO2-N (dissolved nitrite)ISO 6777:1984 + AC:2001 0.054mg/L
NO3-N (dissolved nitrate)ISO 7890-3 3.22mg/L
PO4-P (dissolved phosphate)ISO 6878 3.90.29mg/L
pHISO 105236.97.5
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Civzele, A.; Mezule, L. Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi. J. Fungi 2022, 8, 1232. https://doi.org/10.3390/jof8111232

AMA Style

Civzele A, Mezule L. Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi. Journal of Fungi. 2022; 8(11):1232. https://doi.org/10.3390/jof8111232

Chicago/Turabian Style

Civzele, Anna, and Linda Mezule. 2022. "Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi" Journal of Fungi 8, no. 11: 1232. https://doi.org/10.3390/jof8111232

APA Style

Civzele, A., & Mezule, L. (2022). Microalgae Harvesting after Tertiary Wastewater Treatment with White-Rot Fungi. Journal of Fungi, 8(11), 1232. https://doi.org/10.3390/jof8111232

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop