Indigenous Microalgae Research Articles

Pilot-scale bioremediation of rare earths wastewater by Chlamydomonas sp. YC

The extraction of rare earth elements (REEs) through in-situ leaching with ammonium sulphate [(NH4)2SO4] had resulted in the production of a large volume of ammonium-rich wastewater, causing severe environmental pollution. This study aimed to assess the ability of an indigenous microalga Chlamydomonas sp. YC, isolated from REEs wastewater, to directly treat real REEs wastewater under outdoor conditions in 50 L airlift photobioreactors (AL-PBRs) and 5.0 m3 open race-way photobioreactors (ORWPs). Additionally, the harvested Chlamydomonas sp. YC biomasses from these two pilot photobioreactors were comprehensively analyzed to evaluate the nutritional values. The results showed that Chlamydomonas sp. YC in AL-PBRs exhibited higher biomass production (1.1 g/L), greater removal efficiencies in NH4+-N (24.9%) and total nitrogen (20.4%), as well as higher CO2 fixation rate (125.0 mg/(L·d)), compared to those of ORWPs. Moreover, the Chlamydomonas sp. YC biomasses obtained from the two pilot photobioreactors contained 44.5% and 49.4% protein, 9.1% and 14.3% lipids. Moreover, Chlamydomonas sp. YC in the two pilot photobioreactors displayed essential amino acid indexes (EAAI) of 0.900, which was higher than that of soybean protein (0.657), indicating superior nutritional values. In conclusion, the implementation of the process involving Chlamydomonas sp. YC in AL-PBRs under outdoor conditions holds promise as a coupled microalgal biotechnology for the simultaneous removal of NH4+-N from REEs wastewater, and the capture of CO2 for the production of valuable biomass.

Enhancing Sewage Sludge Stabilization, Pathogen Removal, and Biomass Production through Indigenous Microalgae Promoting Growth: A Sustainable Approach for Sewage Sludge Treatment

Sewage sludge (SS), a byproduct of wastewater treatment plants, poses significant environmental and health risks if not properly handled. Conventional approaches for SS stabilization often involve costly and energy-consuming processes. This study investigated the effect of promoting native microalgae growth in SS on its stabilization, pathogen bacteria removal, and valuable biomass production. The effect on settleability, filterability, and extracellular polymeric substances (EPSs) was examined as well. Experiments were conducted in photobioreactors (PBRs) without O2 supply and CO2 release under controlled parameters. The results show a significant improvement in SS stabilization, with a reduction of volatile solids (VSs) by 47.55%. Additionally, fecal coliforms and E. coli were efficiently removed by 2.25 log and 6.72 log, respectively. Moreover, Salmonella spp. was not detected after 15 days of treatment. The settleability was improved by 71.42%. However, a worsening of the sludge filterability properties was observed, likely due to a decrease in floc size following the reduction of protein content in the tightly bound EPS fraction. Microalgae biomass production was 16.56 mg/L/day, with a mean biomass of 0.35 g/L at the end of the batch treatment, representing 10.35% of the total final biomass. These findings suggest that promoting native microalgal growth in SS could be sustainable and cost-effective for SS stabilization, microalgal biomass production, and the enhancement of sludge-settling characteristics, notwithstanding potential filtration-related considerations.

Isolation and characterization of native microalgae with potential for phycoremediation of heavy metal contaminated water

ABSTRACT The capacity of living algal cells to efficiently eliminate metals from water is well known and achieved through the mechanisms of biosorption and bioaccumulation. These investigations highlight the potential of indigenous microalgae for the elimination of toxic elements such as cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb) from aqueous solutions. To identify algal strains that are effective in removing heavy metals, samples of soil and water were collected from areas contaminated with industrial and municipal effluents. Among the 11 isolates obtained from various sites contaminated with heavy metals, three isolates (designated as A, I and K) were able to tolerate both the threshold and double threshold levels of the tested heavy metals. Subsequent liquid assays confirmed the efficiency of the three selected algal isolates in removing heavy metals, with isolates A and I demonstrating effectiveness in removing all tested heavy metals, exhibiting removal rates of cadmium ranging from 40% to 80%, cobalt ranging from 20% to 60%, chromium up to 90%, nickel ranging from 40% to 90%, and lead ranging from 50% to 70%. Isolate K displayed the highest efficiency in only removing lead, specifically 86.23% at 21 DAI (Days After Inoculation), and therefore was not chosen for further characterization. Through morphological and molecular characterization, isolates A and I were identified as Coelastrella thermophila AAU BR A and Chlorella sp. AAU BR I, respectively. In conclusion, the results demonstrate that the native algal isolates have the potential to serve as eco-friendly agents for remediating heavy metal-contaminated water.

Heavy Metal Scavenging Potential of Indigenous Microalgae of Bangladesh: A Study on its Application in Textile Effluent Treatment

Heavy Metal Scavenging Potential of Indigenous Microalgae of Bangladesh: A Study on its Application in Textile Effluent Treatment

Assessment of heavy metals and environmental stress conditions on the production potential of polyunsaturated fatty acids (PUFAs) in indigenous microalgae isolated from the Gulf of Mannar coastal waters.

The present study evaluated the effects of heavy metals, viz., lead, mercury, and cadmium, on growth, chlorophyll a, b, c, carotenoids, and PUFA content of marine microalgae Chlorella sp. and Cylindrotheca fusiformis. At 96-h exposure, the IC50 values for Hg2+, Pb2+, and Cd2+ were 0.85mg/L, 2.4mg/L, and 5.3mg/L respectively, in Chlorella sp. In C. fusiformis, IC50 values for Hg2+, Pb2+, and Cd2+ were 0.5mg/L, 1.2mg/L, and 3mg/L respectively. The pigment contents of both microalgae were significantly affected upon heavy metal exposure. In Chlorella sp. and C. fusiformis, the exposed concentrations of Hg2+ averagely decreased the PUFA content by 76.34% and 78.68%, respectively. Similarly, Pb2+-exposed concentrations resulted in 54.50% and 82.64% average reductions in PUFA content of Chlorella sp. and C. fusiformis, respectively. Cd2+-exposed concentrations showed 32.58% and 40.54% average reduction in PUFA content of Chlorella sp. and C. fusiformis, respectively. Among the environmental stress conditions, the dark treatment has increased total PUFA content by 6.63% in Chlorella sp. and 3.92% in C. fusiformis. It was observed that the 50% nitrogen starvation (two-stage) significantly improved the PUFA production from 26.47 ± 6.55% to 40.92 ± 10.74% in Chlorella sp. and from 11.23 ± 5.01 to 32.8 ± 14.17% in C. fusiformis. The toxicity for both microalgae was followed in the order Hg2+ > Pb2+ > Cd2+. Among the two species, Chlorella sp. has shown a high tolerance to heavy metals and can be effectively utilized in PUFA production.

Lipid Yields and Fatty Acid Composition if Indigenous Microalgae, Isolated from the Beira, and Diyawanna Urban Lakes, for Sustainable Biofuel Production in Sri Lanka


 Biofuels are carbon-neutral combustibles produced from renewable biomass. Third generation biofuels, derived from microalgal biomass, are distinctly superior to their preceding generations, due to higher productivity and resource use efficiency of microalgae compared to conventional energy crops. It is a viable source of sustainable energy for our country due to the availability of water, ambient temperatures and year-round sunlight needed for microalgae cultivation, and most importantly, the abundance of diverse microalgae species. However, these native microalgae are relatively unexplored for their productivities and thereby, greatly underutilized. This research was aimed to investigate the lipid yields and fatty acid compositions of local freshwater microalgae, and to identify their potential for biodiesel production. This was carried out by (1) microalgae isolation and morphological identification (2) microalgae cultivation (3) biomass harvesting, lipid extraction, gravimetric measurement of extracted lipids and (4) acid-catalysed transesterification, followed by GCMS analysis of the biodiesel product. Chlorella sp., Chlorococcum sp. and Chlamydomonas sp. were isolated from Beira/ Diyawanna Lakes using streak plate technique in solid standard BBM media. They were next cultivated under axenic conditions in liquid standard BBM media under 16: 8 (light: dark), at 25°C for 20 days in duplicates. The biomass was then harvested using alum, dried to reach a constant weight and the Bligh and Dyer lipid extraction was done in triplicate. The extracted lipids were trans-esterified with methanol, using sulfuric acid catalyst at 90° C for 60 minutes. The separated product was analysed by GCMS. Chlorella sp., Chlorococcum sp. and Chlamydomonas sp. cultivated under standard conditions gave average lipid yields of 11.34±1.01%, 15.00±1.40% and 2.10±0.50% respectively. Average lipid yield of Chlamydomonas sp. was significantly lower than the other two species at 95% confidence level (Two-sample T test on SPSS Version 21). GCMS analysis of the biodiesel product from Chlorella sp. indicated significant levels of saturated fatty acids including palmitic and stearic acids, monounsaturated fatty acids like cis-11- eicosenoic acid and polyunsaturated fatty acids including linoleic and linolenic acids. The fatty acid ratios were used to calculate the saturation value, cetane number, density, iodine value and pour point of the produced biodiesel. These quality parameters were in accordance with the ASTM D6751- 20a standards. Therefore, with a substantial yield and fatty acid composition of intracellular lipids, this local species of Chlorella can be a prospective candidate for sustainable bioenergy production in Sri Lanka.
 
 Keywords: Chlorella, Chlorococcum, Chlamydomonas, Microalgal lipids, Biodiesel

Livestock wastewater bioremediation through indigenous microalgae culturing as a circular bioeconomy approach as cattle feed

Growing human population demands the enhancement intensive livestock activities, which lead to severe environmental issues like water pollution. Cattle wastewater is rich in some inorganic pollutants, mainly nitrogen and phosphorous, which might constitute a risk to water bodies. Considering this scenario, microalgae's capacity to develop within manure wastewater is attracting interest, mainly for simultaneous wastewater bioremediation and biomass production. The aim of this work was evaluating the response of several microalgae strains to increasing percentages of unsterilized cattle farm wastewater. Moreover, this study also analyses the possibility of enhancing the development of indigenous native microalgal strains, to create a bioremediation system based on previously adapted species, which specific diversity was determined through taxonomic techniques. Two monospecific Chlorophyceae strains were used: Chlorella sp. and Coelastrella cogersae; and one Cyanobacteria strain: Arthrospira platensis. Experimental assays were conducted in 6 groups and triplicates with increasing percentages of Livestock wastewater (LW): control, 15, 25, 35, 50 and 70 %. All the strains tested showed that cattle wastewater represented a source of metabolic stress for microalgae development. Nevertheless, the autochthonous microalgal bloom showed better results in terms of tolerance to wastewater percentage and development under same conditions Laboratory scale results showed that microalgae could develop with optimum results in presence of 15 % of wastewater, reaching absorbance values close to 90 % of the achieved by control cultures. Moreover, indigenous microalgae cultures were scaled up to open type industrial systems (raceways) and influence of their growth on wastewater composition was evaluated. Results showed a severe reduction of the concentration of nitrates to 43.4 (mg·L−1) (20 % of initial measurements). Moreover, the obtained biomass showed a biochemical profile similar to traditional crops, in terms of proteins and carbohydrates (48 and 41 % respectively), suggesting that this biomass could be further valuated into cattle feed as a circular economy approach.

Experimental Assessment of Lipid Yield and Phycoremediation Potential of Five Indigenous Microalgae Under Various Nutrient Regimes

Experimental Assessment of Lipid Yield and Phycoremediation Potential of Five Indigenous Microalgae Under Various Nutrient Regimes

Cattle wastewater treatment using green microalga Coelastrella sp. KNUA068 as a promising bioenergy feedstock with enhanced biodiesel quality.

Global water scarcity increased the demand for clean water, leading to attention on microalgae-based biological treatment for wastewater due to economic feasibility and sustainable biomass applications. This study isolated indigenous microalga Coelastrella sp. KNUA068 from a wastewater treatment plant, observed its admissible growth rate in diluted cattle wastewater (DCW), and used it for wastewater treatment analysis. The microalga showed high growth rates in indoor and outdoor cultivation with 100% DCW. In addition, the ammonia nitrogen and nitrate nitrogen removal rates of the microalga were 69.97 and 60.35%, respectively, in indoor cultivation, and 50.63 and 67.20%, respectively, in outdoor cultivation. Carotenoid content analysis revealed lutein as the highest productivity carotenoid, and zeaxanthin production was higher in outdoor cultivation. The biomass exhibited suitable biodiesel quality with a cetane number of 50.8 for high-quality biodiesel production. Coelastrella sp. KNUA068 demonstrates potential for bioenergy feedstock, carotenoid production, and wastewater treatment.

Soil health improvement by inoculation of indigenous microalgae in saline soil.

Using biological methods to improve saline soils is recognized as an eco-friendly and sustainable way. In this study, two indigenous algae YJ-1 and YJ-2 screened from salinized farmland were inoculated into saline soils with different salinization levels to investigate their potential in enhancing soil health by laboratory microcosm experiment. The results showed that individual inoculation of the two algae quickly resulted in the formation of algal crusts, and the chlorophyll content in the saline soils gradually increased with the incubation time. The soil pH decreased significantly from the initial 8.15-9.45 to 6.97-7.56 after 60-day incubation. The exopolysaccharides secretion and the activities of catalase, sucrase, and urease in saline soils also increased. Microalgal inoculation increased soil organic matter storage, while decreasing the available nutrient contents possibly due to the depletion of microalgal growth. PCA and PCC results identified that microalgal biomass as the predominant variable affecting soil quality. Overall, these data revealed the great potential of microalgae in the amelioration of saline soils, especially in pH reduction and enzyme activity enhancement. This study will provide the theoretical foundation for improving saline soils via algalization.

Abiotic factors improving fatty acid profiling of freshwater indigenous microalgae isolated from Kumaun region of Uttarakhand, India.

Microalgae have grabbed huge attention as a potential feedstock for biofuel production in response to the rise in energy consumption and the energy crisis. In the present study, indigenous microalgal strains were isolated from four freshwater lakes in the Kumaun region, Uttarakhand, India. Based on growth and lipid profiles, the four best-performing isolates were selected for further experiments. Initial identification of isolates was done by morphological observations, which were further validated by molecular identification using ITS sequencing. The screened cultures were subjected to abiotic stress conditions (varying concentrations of nitrogen and different temperatures) to monitor the biomass, lipid accumulation, and biochemical compositions (chlorophyll and carotenoids). The quantification of fatty acids was checked via gas chromatographic analysis. The strains were identified as KU_MA3 Chlamydopodium starrii, KU_MA4 Tetradesmus nygaardii, KU_MA5 Desmodesmus intermedius, and KU_MA6 Tetradesmus nygaardii. KU_MA3 Chlamydopodium starrii showed the best results in terms of growth and lipid production at 21 °C and 0.37 g/L NaNO2 concentration. The percentage of fatty acid methyl esters (FAMEs) attained >80% and met the standard for biodiesel properties. The strain has the potential to attain higher biomass and accumulate higher lipid content, and after some more studies, it can be used for upscaling processes and large-scale biodiesel production.

Biodiesel production and simultaneous treatment of domestic and livestock wastewater using indigenous microalgae, Chlorella sorokiniana JD1-1

In this study, the potential of Chlorella sorokiniana JD1-1 for biodiesel production was evaluated using domestic wastewater (DWW) as a diluent for locally-generated livestock wastewater (LWW). This strategy aimed to provide sustainable wastewater treatment, reduce environmental impacts, enhance cost-effectiveness, and promote biodiesel production. LWW was diluted with tap water and DWW at ratios of 75%, 50%, and 25% (v/v), and the effects on microalgal growth, nutrient removal efficiency, and lipid yield were evaluated. Although the maximum biomass concentration was observed in the artificial growth medium (BG-11) (1170 mg L−1), 75% dilution using tap water (610 mg L−1) and DWW (780 mg L−1) yielded results comparable to the exclusive use of DWW (820 mg L−1), suggesting a potential for substitution. Total nitrogen (TN) removal rates were consistently high under all conditions, particularly in samples with higher concentrations of LWW. Conversely, total phosphorus (TP) concentrations decreased under most conditions, although some displayed large increases. Further studies are necessary to optimize the nutrient balance while maintaining economic feasibility and maximizing biodiesel production.

Enhancing carotenoid production and exploring the potential use of microalga Desmodesmus cf. pleiomorphus DSHM22 as a biodiesel feedstock through photoheterotrophic cultivation

Improving biomass and value-added compound production is crucial for the industrial application of microalgae, achieved through the utilization of low-cost nutrients and various cultivation modes. This study aimed to enhance the biomass and biochemical production of the indigenous microalgae by comparing different cultivation modes. Among six algal strains obtained from the East Sea in South Korea, Desmodesmus cf. pleiomorphus DSHM22 exhibited the highest biomass productivity (0.0118 g L−1 d−1) and was selected for optimization. Algal growth responses were assessed under four commercially available soluble fertilizer media to identify a cost-effective nutrient substrate. The most effective fertilizer demonstrated 2.2-fold higher growth compared to the BG-11 algal medium after 14 days. Glucose was supplemented in the culture medium to evaluate organic carbon availability under light and dark conditions. While no growth responses were observed under glucose-supplemented dark condition, the highest biomass production (approximately 1.22 g L−1) was achieved under glucose-supplemented light condition. The algal strain showed growth under both photoautotrophic (PA) and photoheterotrophic (PH) conditions, excluding the heterotrophic mode. Biochemical accumulations were compared by analyzing photosynthetic pigments and fatty acids under both PA and PH modes. The algal strain effectively produced lutein, neoxanthin, and omega-3, 6, and 9 fatty acids. Although PH condition yielded significantly higher biochemicals and lipid production compared to PA condition, both culture conditions exhibited similar fatty acid compositions and biodiesel properties. This study suggests that PH cultivation is an effective approach for producing value-added biochemicals and biodiesel using microalga D. cf. pleiomorphus DSHM22.

Nutritional profile, bioactive compounds, and antioxidant activity of microalgal strain, Amphora sp., isolated from the Cape coastal waters, South Africa

Microalgae represent a potential source of renewable nutrition, and there is growing global interest in algae-based dietary supplements. However, the selection of suitable and indigenous microalgae species is a fundamental requirement in developing value-added bioactive compounds in the food industry. The proximate composition, fatty acids, amino acids, and mineral profile, as well as bioactive compounds and antioxidant activity of an unexplored diatom strain, Amphora sp. WCA23.2, isolated from the Cape coastal waters, South Africa, were evaluated as a potential nutraceutical. The Amphora sp. WCA23.2 biomass had 44.2% ash, 28% carbohydrates, 15% protein, and 4% lipids. The fatty acid profile revealed that the diatom accumulates a significant amount of omega-7-monounsaturated fatty acid palmitoleic acid (24.50 mg/g), while the amino acid profile demonstrated that it contained all the nine essential amino acids. The antioxidant activities of the diatom extracts showed that the methanolic extract displayed the highest DPPH radical scavenging activity (1.90±0.11 mg GAE/g dry weight (DW)) and the lowest IC50 in all the antioxidant indices evaluated. These results suggest that Amphora sp. WCA23.2 biomass and its extracts can be utilized as a potential source of ingredients and nutraceuticals in food systems for humans.

Microalgal-bacterial aerobic granular sludge for old leachate treatment: Development, performance, and lipid production

A lab-scale photo bio sequencing batch reactor (PSBR) was used to develop microalgal-bacterial aerobic granular sludge (MB-AGS) for old leachate treatment by seeding activated sludge, while indigenous microalgae were allowed to grow naturally. Upon 100 days of experiment, mature MB-AGS was successfully developed with an average diameter of 2.5 ± 1.5 mm and excellent settling properties, with a settling velocity of 39 ± 24 m/h. The biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia (NH4+-N), total nitrogen (TN), and total phosphorus (TP) removal efficiencies were 80 ± 14%, 95 ± 2%, 88 ± 14%, 56 ± 16%, and 57 ± 14%, respectively. The shift in microbial populations were also examined, in which the abundant EPSs producing bacteria in the system could be one of the reasons behind the successful transformation of activated sludge flocs to mature MB-AGS. Furthermore, lipid was able to be extracted from the MB-AGS, in which the lipid production was 9.35 ± 1.1 mg/g-SS, accounting 0.56 ± 0.07 mg/L.d of lipid productivity.

Biomass and lipid production by the native green microalgae Chlorella sorokiniana in response to nutrients, light intensity, and carbon dioxide: experimental and modeling approach.

Introduction: Microalgae are photosynthetic cells that can produce third-generation biofuels and other commercial compounds. Microalgal growth is influenced by two main parameters: light intensity and carbon dioxide concentration, which represent the energy and carbon source, respectively. For photosynthesis, the optimum values of abiotic factors vary among species. Methods: In this study, the microalga Chlorella sorokiniana was isolated from a freshwater lake. It was identified using molecular analysis of the ribosomal internal transcribed spacer. A single-factor design of experiments in 250-mL Erlenmeyer flasks was used to evaluate which concentrations of nitrogen and phosphorus increase the production of biomass and lipids. The response surface methodology was used with a 32-factorial design (light intensity and CO2 were used to evaluate its effect on biomass, lipid production, and specific growth rates, in 200-mL tubular photobioreactors (PBRs)). Results and Discussion: Low levels of light lead to lipid accumulation, while higher levels of light lead to the synthesis of cell biomass. The highest biomass and lipid production were 0.705 ± 0.04g/L and 55.1% ± 4.1%, respectively. A mathematical model was proposed in order to describe the main phenomena occurring in the culture, such as oxygen and CO2 mass transfer and the effect of light and nutrients on the growth of microalgae. The main novelties of this work were molecular identification of the strain, optimization of culture conditions for the indigenous microalgae species that were isolated, and formulation of a model that describes the behavior of the culture.

Biomass Production of Subang Isolated Scenedesmus in Tube-shaped Photobioreactor with the Exposure of Audible Sound (Music): Photobioreactor Improvement Strategy

The cultivation of Subang Isolated Scenedesmus in tube-shaped photobioreactors (PBRs) with the exposure of audible sound (music) was done. The study was done to know the effect of different music to the growth and culture appearance of Subang Isolated Scenedesmus. Subang Isolated Scenedesmus itself is Indonesia’s indigenous microalgae from Subang, West Java. This study was using three groups of Subang Isolated Scenedesmus PBRs. One group was control group and not exposed to any sound (Control-PBR), one group was exposed to music called “Blues for Elle” (PBR-A), and another group was exposed to music called “Bloom” (PBR-B). Based on 8 days of observation, it is known that Subang isolated Scenedesmus in PBR-A has the highest average cell density at the peak phase (1.81±0.16 x 105 cells/mL), highest growth rate (26.22 % per day), and most intense green color compared to Subang isolated Scenedesmus in PBR-B and Control-PBR. Related-Samples Friedman’s Two-Way ANOVA by Ranks test has proven that the average cell density value of Subang isolated Scenedesmus in Control-PBR, PBR-A, and PBR-B are not the same (α = 95%, sig = 0.013). Therefore, different audible sound (music) with certain intensity and frequency may affect the growth of Subang Isolated Scenedesmus differently

Combination of non-sterilized wastewater purification and high-level CO2 bio-capture with substantial biomass yield of an indigenous Chlorella strain

The indigenous microalga Chlorella sorokiniana NBU-3 grown under air, 5 %, 15 %, and 25 % CO2 supply was evaluated to determine its potential for flue gas bio-capture, nutrient removal capacity and biomass yield using non-sterilized wastewater as growth medium. The results indicated that C. sorokiniana NBU-3 exhibited high nutrient removal efficiency (>95 % for NH4+-N, TN and TP) with either air or CO2 aeration. 5 %–15 % CO2 supplies promote biomass yield, nutrient utilization and CO2 biofixation of C. sorokiniana NBU-3. In particular, 15 % CO2 promotes C. sorokiniana NBU-3 growth in non-sterilized MW, but inhibits its growth in BG11 medium, indicating the importance of non-sterilized MW and high CO2 aeration concurrence for C. sorokiniana NBU-3 economically practical cultivation. Moreover, the highest values of lipid (27.84 ± 2.12 %) and protein (32.65 ± 4.11 %) contents were obtained in MW with 15 % CO2 aeration. Conceivably, microalgal-bacterial symbiosis may help C. sorokiniana NBU-3 tolerate high concentration of CO2 and promote microalga growth. The succession of the community diversity toward the specific functional bacterial species such as Methylobacillus and Methylophilus (Proteobacteria) which were predicted to possess the function of methylotroph, methanol oxidation and ureolysis would help facilitate the microalgal-bacterial symbiosis and promote the microalgae biomass accumulation with high dosage of CO2 aeration. Overall, these findings clearly highlight the potential of this indigenous microalga C. sorokiniana NBU-3 for industrial-emission level CO2 mitigation and commercial microalga biomass production in MW.

Growth kinetics and metabolic characteristics of five freshwater indigenous microalgae for nutrient removal and biofuel generation: a sustainable approach

Growth kinetics and metabolic characteristics of five freshwater indigenous microalgae for nutrient removal and biofuel generation: a sustainable approach

Enhancement of nutrients recovery and cell metabolism in piggery anaerobic digestate by the co-cultivation of indigenous microalgae and bacteria

For energy-efficient treatment of anaerobic digestate by biological methods, we constructed the native microalgae-bacterial symbiosis systems (Chlorella sp.-Lysinibacillus sp. and Chlamydomonas sp.-Shinella sp.), as well as investigated their nutrient removal, biomass output and chemical composition, and microbial activity during anaerobic digestate treatment. Co-cultures of microalgae and bacteria promoted the synthesis of unsaturated fatty acids, enhanced the tolerance of microorganisms to toxic substances in wastewater, improved photosynthesis of microalgae, and reduced cell mortality. Specifically, bacteria promoted the growth and metabolism of microalgae and further improved the carbon reduction capacity of the system by 22.37%. A ratio of 50:1 in group Chlorella sp.-Lysinibacillus sp. was obtained for the best performance on biomass yield (0.85 g‧L−1) and pollutant removal efficiencies: TOC (48.67%), IC (85.19%), NH4+-N (98.55%), TN (80.35%) and TP (40.62%). The group Chlamydomonas sp.-Shinella sp. achieved the highest biomass yield (1.05 g‧L−1) and the maximum pollutant removal (TOC: 39.05%, IC: 85.92%, NH4+-N: 97.82%, TN: 83.32%, TP: 39.25%) at a ratio of 20:1. This study provides an environmentally-friendly strategy with low carbon emission and energy consumption for anaerobic digestate purification.