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The increased demand for sustainable and ecological agricultural tools to decrease the dependency on chemical fertilizers has surged throughout the last years. Cyanobacteria and microalgae-based biostimulants offer an innovative solution and ecofriendly platform for plant biostimulant production, due to their metabolic diversity and valuable value-added products. Focuses were directed especially towards marine and freshwaters microalgae whereas indigenous soil microalgae were rarely prospected for their biostimulant potential. The aim of this study was to assess the biostimulant activity of the soil microalga Chlorella vulgaris on seed germination performance. The effects of extraction method and plant choice on the biostimulant activity of C. vulgaris were investigated via the comparison of the composition and activity of four extraction techniques (aqueous extraction, acid hydrolysis extraction, organic solvent extraction, microwave-assisted aqueous extraction) on two different plant seed models (wheat and tomato). Seeds were soaked with four different concentrations (from 0.1 g L−1 to 2 g L−1) to determine dose-dependent effects. Results demonstrated significant differences in extracts biochemical composition and biostimulant effects on seed germination enhancement. Extract composition in terms of biomolecules concentrations revealed significant dissimilarities. Seed germination indices and biometric parameters were significantly improved by lower doses (0.1 g L−1 and 1 g L−1), while higher doses (2 g L−1) usually revealed negative effects. The best increases in wheat and tomato seed germination parameters were reached by using acid hydrolysis, aqueous and microwave-assisted aqueous extracts at lower doses. Thus, our results highlight that aqueous extract-based methods were as effective as other techniques. These findings shed light on the advantages of eco-extraction processes and microalgae-based aqueous extracts as eco-friendly biostimulants eligible for sustainable agriculture. [ABSTRACT FROM AUTHOR]

In the scope of vegetarian diets, cobalamin (CBL or vitamin B12) remains a particular concern, as it is mostly absent from natural, vegetarian foods. As such, vegetarians must rely on supplementation or enriched food products, to fulfil their recommended daily intake of the vitamin. The potential of microalgae is of extreme importance in this context, given the fact that they may absorb exogenous CBL and display significant levels of the vitamin. Therefore, it is crucial to establish fast and reliable B12 determination methods, to accurately characterize these products or ingredients and conclude about their role as CBL sources. To that extent, this work presents the application of the AOAC's final action method 2014.02 on the determination of total CBL in selected, commercial, microalgae and cyanobacteria powder samples. Four variants of Chlorella vulgaris, namely organic, smooth, white and honey, as well as Spirulina (Arthrospira platensis) were investigated. High-performance liquid chromatography coupled with ultraviolet (UV), diode-array detection (HPLC-DAD) was implemented in the analysis of microalgal extracts. After slight adaptation and optimisation of the extraction and analysis procedures, namely to allow lower sample amounts, it was determined that the different commercial Chlorella products, organic, smooth, white and honey have total CBL concentrations of 1063 ± 158 μg (100 g)-1, 482 ± 55 μg (100 g)-1, 681 ± 87 μg (100 g)-1 and 660 ± 68 μg (100 g)-1, respectively. Analysis of Spirulina did not yield any measurable levels of CBL in any of the purified extracts. Despite the obtained results displaying the same order of magnitude previously determined in similar microalgal products, these CBL values are amongst the highest concentrations found. Therefore, even considering the known limitations in bioaccessibility and bioavailability of CBL in microalgae, it is possible to conclude that these results stand for the inclusion of these products in vegetarian foods or as food supplements, as good potential sources of CBL, which is generally lacking in vegetarian diets. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the novel valorization of wastewater through the desalination process of concentrated saline water (CSW) originating from the semiarid regions of Brazil using the growth of two microalgae and modeling their growth using a kinetic model. Chlorella vulgaris and Ankistrodesmus fusiformis were cultured for 15 days in BG 11 medium that was partially replaced with wastewater, and the data from the best growing conditions were fitted to the model of Gompertz. The CSW had a low heavy metal concentration and both algae grew under all conditions studied. However, each microalga exhibited a different behavior under the same conditions. C. vulgaris remained only in the adaptation phase when it was cultured in 100% CSW. In contrast, A. fusiformis was only 3 days in the lag phase and had 67% more biomass than C. vulgaris. 75% CSW was best for both microalgae. This study demonstrates a circular bioeconomy model that can be applied to semiarid regions to provide water and food security for the local population. The potential of A. fusiformis has also been highlighted; however, it has not yet been explored in the field of microalgae culture. [ABSTRACT FROM AUTHOR]

'New Red Fire' is one of most cultivated cultivars of leafy lettuce in Europe. Considering lettuce is a salt-sensitive crop, assessment of its responses to salt stress and applying efficient techniques to alleviate stress effects are highly important. Here, the influence of seed priming with different seaweed (Ascophyllum nodosum (Sc) and Sargassum angustifolium (Sa)) and microalgal (Chlorella vulgaris (Cv) and Arthrospira platensis (Sp)) extracts on germination indices of leafy lettuce under salt stress conditions (irrigation with saline water with EC levels of 1.37, 2.5, 4, 5.5 and 7 dS m-1) was investigated (with a modeling approach). Under control level of salinity, highest germination percentage was recorded in seeds primed with microalgae extracts. Based on Logistic model, the highest (a) parameter (predicted germination percentage) was for seeds primed with Cv (75.09). Also, the highest (x50) parameter (salt tolerance threshold) was recorded in Cv-primed seeds (15.76 dS m-1). According to liner regression model, (b) parameter (reduction rate of germination speed per unit increase in salinity level) of Cv-primed seeds was lower than that of Sp-, Sc- and Sa-primed seeds. In conclusion, it is recommended to apply C. vulgaris extract as seed priming solution to alleviate negative effects of salt stress on germination indices and seedling growth parameters of leafy lettuce. It is also recommended to quantify the germination responses of leafy lettuce to the other biotic and abiotic stresses for future studies. [ABSTRACT FROM AUTHOR]

Microalgae are regarded as a promising source of renewable energy and high-value compounds. To date most large-scale microalgae cultivation is located in hot low-latitude regions; however, high temperature and high solar intensity create a risk of overheating during summer days. Here we explore the option of microalgae cultivation in low temperature regions. The impact of low temperature on microalgae growth is rarely considered in studied species and strains. To assess the optimum temperature and to test the ability to grow in low temperatures, we tested the effect of environmental temperatures ranging from 8 to 32 °C on the growth of the green microalga Chlorella vulgaris 211/11j. This strain was selected as a candidate strain for outdoor cultivation after an extensive literature review. The results indicate that C. vulgaris 211/11j has a lower optimal growth temperature than some other strains of C. vulgaris and exhibits optimal growth over a wide temperature range from 20 to 28 °C. Moreover, we demonstrate that the strain can grow successfully at low environmental temperatures that are below the optimum of this strain. Therefore, we suggest C. vulgaris 211/11j as a potential strain for cultivation in outdoor open ponds exposed to changing environmental temperatures in cooler climate regions. [ABSTRACT FROM AUTHOR]

The effects of silicon oxide nanoparticles (SNPs) on the growth of Chlorella vulgaris and its influence on biodegradation of pyrene (PYR) were evaluated. Addition of SNP to culture media at low concentrations (0.5–5 mg L−1) showed beneficial effects on growth and biomass of C. vulgaris. SNP at 1 mg L−1 showed 13% enhancement in biomass during 7 days of cultivation of C. vulgaris. The total chlorophyll content and PSII activity were highest in 1 mg L−1 SNP. We observed the toxicity mitigating aspect of SNPs (1 mg L−1) when algae were grown in a medium containing PYR (5 mg L−1). Biodegradation of PYR by C. vulgaris was significantly improved (31%) in the presence of 1 mg L−1 SNP in 5 days. The study of enzyme activity demonstrated that catechol 2,3 dioxygenase activity, which has an important role in the biodegradation of PYR, was upregulated in algal cells treated with SNP + PYR, whereas dehydrogenase activity which is also responsible for degradation of organic chemicals, was unaltered. This result proves the role of SNP in PYR biodegradation capacity of C. vulgaris through involvement of the dioxygenase pathway. Current findings suggest the possibility of SNP addition to the microalgal media to improve algal growth as well as PYR bioremediation capacity. [ABSTRACT FROM AUTHOR]

With the growing human population, greenhouse gases and global temperature are increasing calling for sustainable biorefineries to convert low-value side streams into high-value products. In this study, the remaining hemicellulosic sugary waste fraction of a wheat straw biorefinery approach, without any pretreatment, was applied as a medium supplement for Chlorella vulgaris cultivation. Next to oligomeric and monomeric sugars, the waste stream contained hydrolysis by-products, such as furfural, 5-hydroxymethylfurfural and acetic acid. Despite the presence of these growth inhibitors, C. vulgaris cultivation was possible. Addition of 2.5% (v/v) of wheat straw hydrolysate to BG11-medium boosted chlorophyll content in C. vulgaris by 40% compared to photoautotrophically grown cells solely cultivated on defined media. As of now, this is the highest chlorophyll content obtained from a cultivation of C. vulgaris on a medium supplemented with a waste stream. Overall, our results demonstrate that wheat straw hydrolysate increases chlorophyll biosynthesis, improving the nutritional value of C. vulgaris biomass for food and feed applications. Hence, valorization of this hemicellulosic sugary fraction results in an additional high-valued product contributing towards the wheat straw biorefinery. [ABSTRACT FROM AUTHOR]

The present study evaluated the effects of melatonin and light wavelengths on the growth rate of Chlorella vulgaris and on increasing nutrient removal from dairy wastewater. The microalgae were cultured under red, blue, green and white light emitting diodes (LEDs) with different concentrations of melatonin in dairy wastewater for 18 days. In melatonin-free samples, the maximum dry weight and cell number were observed under red, blue, green, and white LEDs, respectively. All concentrations of melatonin except 500 µM in the wavelengths used caused a significant increase in dry weight and cell number compared to samples under the same wavelength without melatonin. The greatest amount of dry weight and cell number was observed in the microalgae treated with 10 µM melatonin under red light LED. The use of red LED and 10 μM melatonin increased dry weight and cell number by about 200% compared with samples grown under white light. Nitrate, phosphate and sulfate removal were 92%, 85% and 80%, respectively, under red LED and 10 µM melatonin. These values were 3.02, 2.83, and 2.68 times higher, respectively, than samples grown under white light. Among all treatments, the maximum decrease in COD (80.6%) and BOD (88.65%) removal was observed with red LED and 10 µM melatonin. Moreover, the greatest effect of melatonin in increasing TOC removal was observed with red LED (71.03%). The results show that the use of red LEDs and melatonin significantly increased the growth of C. vulgaris in dairy wastewater, thus improving the wastewater treatment parameters. [ABSTRACT FROM AUTHOR]

Brazilian ethanol production generates approximately 351 billion liters yearly of vinasse that is mostly used for fertigation, but with significant environmental impact. This research aims at comparing the growth of Chlorella vulgaris on three different media preparation using raw vinasse, diluted vinasse, and vinasse treated by anaerobic digestion; all under four distinct treatments or supplementations (antibiotic, nitrogen and phosphorous). The results show that C vulgaris grows poorly on raw vinasse alone or after supplementation. However, 11–13 mg L−1 day−1 of algal oil can be produced with diluted or anaerobically treated vinasse. The first would require antibiotic, nitrogen and phosphorous supplementation and the later only antibiotic supplementation. Whilst using diluted vinasse may reduce work input, it requires significant amounts of clean water. The use of anaerobically treated vinasse requires some additional work and investment, but it can generate 122 mL CH4 g−1CODvinasse (10–26.4 m3 of biogas from 1m3 of vinasse). Thus, the association of methane and algal oil production from vinasse is an effective approach for removing inorganic nutrients and potentially toxic organics from this effluent before discharge. The quality of the algal oil produced is affected by culturing conditions and anaerobically treated vinasse produced the best results in this area according to the estimated parameters of the biodiesel. [ABSTRACT FROM AUTHOR]

The interest in microalgae biofilm-based systems has been increasing lately due to their high potential for biomass production. However, more studies focusing on the first stages of this bioprocess, such as support selection and inoculum properties, which may finally affect biomass productivity, are required. The aim of this study was therefore to assess the impact of support nature and inoculum properties on microalgae biofilm productivity and physiology. Results suggest that physico-chemical properties of the support (micro-texture, hydrophobicity and chemical functional groups) affect the attachment of Chlorella vulgaris. Significant differences in cell-distribution pattern and biofilm structure on polyamide-based (Terrazzo) and cotton-based fabrics were observed. Compared to Cotton, cells grown on Terrazzo showed higher biomass productivity (3.20-fold), photosynthetic capacity (1.32-fold) and carbohydrate pool (1.36-fold), which may be explained by differences in light availability due to support micro-texture. A high inoculum density resulted in a lower biofilm growth, likely due to a lower light/nutrient availability for the cells. Furthermore, when immobilized on fabrics, cells pre-acclimated to 350 μmol photons m−2 s−1 grew faster than those pre-acclimated to low light (50 μmol photons m−2 s−1), demonstrating the influence of light-history of the inoculum cells on biofilm productivity. Therefore, this work confirmed the importance of support and inoculum properties for biofilm-based systems. [ABSTRACT FROM AUTHOR]

Microalgae are known as renewable feedstock for biomass and lipid production. The ability to grow microalgae in wastewater makes their cultivation potentially cost-effective. In this work, the potential of using melatonin and monochromatic light-emitting diodes (LED) to increase lipid accumulation and biomass productivity of microalgae Chlorella vulgaris grown in dairy wastewater was investigated. The experiments were performed under red, blue, green, and white LEDs with melatonin in dairy wastewater. In no-melatonin samples, the maximum biomass productivity was observed in the algae treated with red and blue LEDs, respectively. According to the changes in biomass productivity, the highest content of pigments, carbohydrates, proteins, and lipids was obtained in algae grown with red LED and the lowest amounts of these compounds were observed in white light. Adding 10 µM melatonin to the culture medium improved all results compared to no-melatonin samples. Simultaneous treatment of red LED with 10 µM melatonin increased biomass productivity two-fold compared to white LED without melatonin and was selected as the optimal treatment. The lipid content under optimal treatment reached 44.63% DW compared to the control sample with 23.00% DW. The amount of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) increased by 22 and 8% compared to the control. The percentage of saturated fatty acids (SFAs) decreased from 85.58% in the control samples to 56.93% in the optimal treatment. These results show that red LED can be a new economic treatment to increase the biomass and metabolites of C. vulgaris microalgae in dairy wastewater. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of Arthrospira platensis and Chlorella vulgaris on kefir microbiota, total phenolic content, antioxidant activity, and physicochemical properties such as pH, Brix, total dry matter, and titratable acidity. The results showed that the addition of algae at concentrations of 0.5% (w/v) and 1% (w/v) to the kefir did not change the acceptable physicochemical properties of kefir. The acidity of the microalgae-enriched kefirs increased with increasing algae concentration. Total phenolic content and antioxidant activity of all kefir samples fortified with algae were higher than those of the control. However, the addition of A. platensis exhibited better prebiotic activity than C. vulgaris on kefir microbiota during storage. Principal component analysis and overall results showed that A. platensis was a better candidate for improving the nutritional value of kefir. [ABSTRACT FROM AUTHOR]

Bisphenol A and its structural congeners are increasingly recognized as emerging contaminants with toxic and estrogenic potential that have been widely used in many consumer products. Due to their widespread occurrence in aquatic environment, they could pose risks to the primary producers, such as microalgae. Therefore, the objective of this study was to examine the toxicity of bisphenol A, its six structural congeners, and their mixture towards the green algae Chlorella vulgaris and Desmodesmus armatus. Bisphenol A (average 14 days, EC50: 42.29 mg L−1) exhibited less harmful effect than structural congeners, such as bisphenol AF, bisphenol G, bisphenol X for C. vulgaris (average 14 days, EC50: 22.39 mg L−1) and bisphenol AF, bisphenol G, bisphenol M, bisphenol X for D. armatus (average 14 days, EC50: 27.16 mg L−1), respectively. Moreover, exposure to combined bisphenol A and its structural congeners leads to synergistic effects. Thus, the increased adverse effect caused by complex chemical mixture poses a greater risk to microalgae. The order of toxic effect (14 days, EC50) of individual and combined structural congeners was: bisphenol G > bisphenol X > mixture > bisphenol AF > bisphenol A > bisphenol Y > bisphenol M > bisphenol P for C. vulgaris and mixture > bisphenol G > bisphenol X > bisphenol M > bisphenol AF > bisphenol A > bisphenol Y > bisphenol P for D. armatus, respectively. This is the first time that the toxicity of structural congeners of bisphenol A and its mixture to microalgae is described. Furthermore, these results were conducted to assess potential ecological risk of these compounds in the aquatic environment. [ABSTRACT FROM AUTHOR]

The batch production of Chlorella vulgaris and its potential to profit the remnant nutritional components from ricotta cheese whey (RCW) were evaluated. From a first screening test, undiluted ricotta cheese whey was selected to be used as a growth media in the subsequent assays. Three different RCW pre-treatment methods were tested and compared: centrifugation, heat treatment (HT) and tangential flow microfiltration (TFMF). Based on the results of the screening test, a macronutrient supplementation assay was performed to increase the biomass production. A central composite design was used to analyse the effect of supplementing the media with nitrogen (0; 3.3 and 6.6 g L−1) and phosphorous (0; 0.27 and 0.55 g L−1). Chlorella vulgaris was able to grow in all tested RCW concentrations. All RCW pre-treatment methods resulted in an enhancement of the growth kinetic parameters (GKP) of Chlorella vulgaris. Among them, TFMF technology presented the best performance. The macronutrient supplementation did not show an enhancement in GKP. The scaled-up production until 400 mL batch using micro-filtered RCW showed a μmax value of 0.41 ± 0.05 h−1 (9.9 ± 1.2 day−1), a lag period of 19.9 ± 0.7 h and a Cmax of 2.52 ± 0.09. A final biomass concentration of 2.28 g L−1 was obtained. In addition, chemical oxygen demand (COD), phosphorus and nitrogen removals of 26 ± 1%, 75 ± 1% and 55 ± 1% were respectively achieved. The use of TFMF and Chlorella vulgaris cultivation represents a sustainable proposal for contributing to the circular economy. [ABSTRACT FROM AUTHOR]

Continuous monitoring of biomass concentration in microalgae cultures is essential and one of the most important parameters to measure in this field. This study aims at digital image processing in RGB and greyscale models, being a simple and low-cost method for cell estimation. Images obtained from different photobioreactors with wastewater and at different conditions for the cultivation of Chlorella vulgaris were analyzed. The results suggested that this technique is very effective under controlled lighting conditions, in contrast to photobioreactors placed outdoors and of different design, presenting a lower linearity. The accuracy of the method could be improved with a high-quality charge-coupled device (CCD) camera. The development of efficient methods to assess biomass concentration is an important and necessary step towards large-scale microalgae cultivation. The colour analysis technique has a great potential to meet the needs of monitoring cultures in a cost-effective and automated way using simple and cheap instruments. [ABSTRACT FROM AUTHOR]

Microalgal biofilms are promising sources of sustainable biofuels and bioproducts because of their minimal growth requirements, ability to sequester CO2, and high biomass concentrations. However, strategies to enhance the growth of product-producing species within the biofilm communities must be investigated to optimize the performance and profitability of algal biofilm cultivation systems. Quantitative polymerase chain reaction assays were used to investigate how wastewater, biofilm attachment material, and inoculation strategies influence the abundance of Chlorella vulgaris and Scenedesmus obliquus in biofilms. A 5.6-fold increase in biofilm dry weight was achieved by pretreating reactors with wastewater and using cotton biofilm attachment materials compared to that on non-pretreated polycarbonate attachment materials. Furthermore, depending on the inoculation strategy and the presence of wastewater, the composition of the algal community in biofilms differed from their corresponding suspensions and from the inoculums, highlighting the importance of analyzing the species in algal biofilms in cultivation systems. This study represents the first application of quantitative polymerase chain reaction to estimate cell abundance of C. vulgaris and S. obliquus in cultivated algal biofilms and provides insights into the optimization of algal biofilm cultivation systems for the commercialization of algal biofuels or other bioproducts. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris is known for its protein, growth factor, and nutritional constituents. Chlorella vulgaris was cultivated in a 1000-L outdoor open raceway pond with a maximum volumetric productivity of 130 mg L-1 day-1. The harvested biomass was dried through different methods, viz., sun drying (30 °C), oven drying (60 °C), lyophilization (−110 °C), drum drying (120 °C), and spray drying (100–150 °C). The effect of the drying method on proximate composition, pigments (chlorophyll, carotenoids), bioactive compounds (total phenolic content, flavonoid content), vitamin B12, antioxidant properties (ferric reducing antioxidant power, DPPH, and total antioxidant activity), and the color quality of C. vulgaris biomass was evaluated. Surface characterization by scanning electron microscopy (SEM) and functional group characterization through Fourier transform infrared spectroscopy were also performed. The biomass dried through lyophilization and sun drying retained maximum bioactive compounds and antioxidant activities. In contrast, drum drying resulted in a loss of nutrients, viz., protein (up to 44%), lipid (up to 41%), vitamin B12 (up to 40%), total phenolic content (> 50%), total flavonoid content (> 50%), and antioxidant activity (> 50%). Oven drying led to a loss of 30% in total flavonoid content and 17% in ferric reducing antioxidant power. SEM showed the destruction of cell wall integrity in the drum-dried sample and porous structure in the spray-dried sample. This study suggests that drying methods affect the nutrients and bioactive compounds of C. vulgaris biomass, and therefore a drying method should be selected carefully depending on the end use of the biomass. [ABSTRACT FROM AUTHOR]

The accumulation of nitrogen and phosphorous has detrimental effects on aquatic animals and negatively influences the economic benefits of aquaculture; thus, the control of water quality is of significance for the development of the aquaculture industry. In this study, a coculture system of Chlorella vulgaris + Rhodosporidium sphaerocarpum exhibited superior nitrogen removal performances compared with those of either the Isochrysis galbana + R. sphaerocarpum or the Tetraselmis helgolandica + R. sphaerocarpum coculture systems. The alginate-immobilized C. vulgaris and suspended R. sphaerocarpum coculture system was advantageous in terms of nutrient removal and the inoculum ratio (IR, dry weight of C. vulgaris to dry weight of R. sphaerocarpum) of 5:1 was determined to yield optimal removal performances of nutrients and the chemical oxygen demand (COD), with which 86.20% of the NH4+ content was removed, and 100.00% removal efficiency of NO2−, NO3−, PO43−, and COD was detected after 120 h of incubation. The growth of C. vulgaris and R. sphaerocarpum was enhanced and a biomass productivity of 0.22 g L−1 day−1 was obtained. The sustainability of the optimized microalgae-yeast coculture system was confirmed by steady and consistent removal performances in semicontinuous experiments, removing over 80% of NH4+, 100% of NO3−, and over 90% of NO2−, PO43−, and COD. These results indicated that the optimized microalgae-yeast coculture system developed in our studies might provide a potential method for the biological treatment of aquaculture wastewater. [ABSTRACT FROM AUTHOR]

The effects of light and salt stress (NaCl and MgCl2) on the two-stage cultivation of Chlorella vulgaris, with or without a medium replacement, for the simultaneous production of lipid, carotenoids, and antioxidant compounds were investigated. The highest lipid productivity (15.59 ± 0.10 mg L−1 day−1) was obtained at 5 g L−1 MgCl2 and 140 μmol photons m−2 s−1 light intensity. The saturated fatty acids (SFA) ranged from 52.35–81.64%, monounsaturated fatty acids (MUFA) from 7.38–34.26%, and polyunsaturated fatty acids (PUFA) from 7.25–25.10%, with palmitic (C16:0), stearic (C18:0), and oleic (C18:1) acids as predominant fatty acids. Under high light intensity and nitrogen limitation in the two-stage cultivation, supplementation of 10 g L−1 NaCl with a medium replacement caused a marked increase in the total carotenoids (4.37 ± 0.33 μg mL−1). Cultivation of C. vulgaris in a medium containing 5 g L−1 NaCl or Mg Cl2, with or without a medium replacement step and with exposure to 140 μmol photons m−2 s−1 light intensity, led to enhanced antioxidant activities (65–79%). The different levels of antioxidant activities of the C. vulgaris extracts suggested the variation in the phytochemical compounds, a result of the stressed conditions. [ABSTRACT FROM AUTHOR]

Polysaccharides isolated from algae species have been shown to have various biological properties including immunomodulatory activities. In the present study, the effects of water-extractable polysaccharides from a Chlorella vulgaris biomass on the expression of immunostimulatory cytokines by chicken peripheral blood mononuclear cells (PBMCs) were evaluated. Extracted polysaccharides were fractionated using a DEAE Sepharose FF column yielding two fractions (F1 and F2). Crude polysaccharide (CP) and fractions mostly consisted of carbohydrates (71.9 to 82.9%), protein (6 to 13.8%), and uronic acids (4.8 to 7.9%). Monosaccharide constituents were predominantly galactose (13.1 to 53.2%), glucose (15.3 to 38.6%), mannose (5.5 to 11.2%), arabinose (5.6 to 20.7%), and rhamnose (5.8 to 14.7%). Crude, F1, and F2 polysaccharides contained 1 or 2 sub-fractions with average molecular weight ranging from 19.2 to 161.1 × 103 g mol−1. Evaluation of immunostimulatory activities of CP and fractions (200 to 1000 μg mL−1) revealed significant effects on PBMC interferon-γ (IFN-γ) and interleukin-2 (IL-2) expression. The most potent immunostimulating fraction F1 was consisted of a homogeneous polysaccharide with relatively low molecular weight (23.9 × 103 g mol−1), low structural compactness, and mixed linkages of (→1)-, (1→3)-, (1→3,6)-galactopyranose and -glucopyranose residues. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris, a coccoid green eukaryotic microalga, is a popular food supplement and has been marketed as a nutritional supplement in Asia. Despite numerous reports on the antioxidant property of this species, its toxic effect has not been extensively studied. The aim of this study was to determine the acute oral toxic effect of C. vulgaris on female Sprague Dawley (SD) rats. An acute oral toxicity assessment of C. vulgaris was performed based on the Organization for Economic Cooperation and Development (OECD) Guideline 420. These guidelines are divided into a sighting study and a main study. In the sighting study, C. vulgaris extract was administered orally in sequential doses of 5, 50, 300 and 2000 mg kg−1 body weight (BW) with one rat used for each dosage. Clinical observation and mortality were observed for each rat to monitor signs of toxicity for 14 days. BW and relative organ weight (ROW) were recorded. Blood was collected for liver function test (LFT). Gross pathological evaluations were performed after euthanasia of rats. Haematoxylin and eosin (H&E) staining of the liver and kidney was also performed. The main study was performed based on the highest dose in the sighting study that did not exhibit any signs of toxicity and mortality. For 14 days, clinical observations, BW, and ROW were recorded. Blood from rats in the main study was also measured for LFT, and gross pathological evaluations and H&E staining of the liver and kidney were also performed. The highest dose of 2000 mg kg−1 BW C. vulgaris was used in the main study. No toxicity and mortality were observed in both the sighting study and the main study. Increases in BW were observed in both studies. Gross pathological evaluations showed no signs of organ abnormalities on each organ in the sighting and main studies. The ROW also showed no differences. The values of biochemical parameters in the liver function test showed no differences in the sighting study. However, in the main study, significant decreases in alkaline phosphatase (ALP) and aspartate aminotransferase (AST) were observed on day 14 compared with day 0 (p < 0.05). Chlorella vulgaris showed no toxicity at the dose of 2000 mg kg−1 BW. In conclusion, C. vulgaris can be categorized as unclassified according to the Globally Harmonised Classification System (GHS) for chemical substances and mixtures. [ABSTRACT FROM AUTHOR]

In this study, Chlorella vulgaris treated with static magnetic field (SMF) was investigated in terms of the algal density, biomass, extracellular polysaccharide content and distribution, percentage of algal aggregation, total protein content, enzyme activity, malondialdehyde content, and nutrient removal. The algal density and biomass under 800 G SMF were highest on the 16th day and were 29.02% and 35.67% greater than the control group (0 G group), respectively. Soluble EPS decreased with an increase in magnetic field strength, while bound EPS exhibited an opposite trend. Algal aggregation occurred in all treatment groups, with the aggregation percentage in the high magnetic field-treated groups being lower than that in the control group. Total protein content of the 800 G group was the lowest at 1.13 μg (106 cells)-1 and the enzyme activity of treated algae was higher than that of the control group. SMF affected the growth and reproduction of C. vulgaris by affecting the antioxidant response. [ABSTRACT FROM AUTHOR]

Microalgae as one of the key components of food chains in aquatic environments are promising biological models for investigating gamma irradiation effects on eukaryotic organisms. Understanding resistance mechanisms in these organisms as simple models might illuminate how gamma irradiation resistance improves in these algae and even more complex organisms. The present study aimed to investigate the effects of ionizing irradiation on Chlorella vulgaris as a stress-tolerant microalga and to find how the eukaryotic cells would tolerate such stressful conditions. The physiological responses and biochemical alterations of C. vulgaris were analyzed at three different time points (0, 16, and 48 h) after 600 Gy gamma irradiation. Compared to the control, gamma-irradiated algae had slower growth rate with significantly longer lag phase, less chlorophyll and protein contents at time 0, which were compensated and recovered during the next 48 h. The results also showed spontaneous H2O2 burst accompanied by a higher rate of lipid peroxidation and electrolyte leakage, a rapid increase of catalase activity and more ferric reducing antioxidant power immediately after irradiation. During a 48-h period, most alterations stabilized. Raising trends were observed in the carotenoid contents, the ratios of carbohydrates, amide I and amide II to fatty acids. Principal component analysis and hierarchical clustering suggest two possible distinct mechanisms: a "quick" one including spontaneous responses by boosting H2O2, amplifying enzymatic antioxidant systems, and increasing compatible solutes like proline and a "delayed" responsive strategy including the increase of soluble carbohydrates, carotenoids, and stress-related proteins triggered several hours after irradiation. [ABSTRACT FROM AUTHOR]

The continuous decline in phosphorus (P) resources is a serious global issue. Therefore, it is important to develop methods to recover P from waste and wastewater. Most P ores are currently used in the phosphate form in the agriculture industry and in detergents, which results in a large release of phosphates into natural aquatic environments. Much attention has been given to measuring phosphate levels and monitoring water quality, survey, and control of algal phytoplankton dynamics. However, phosphite is oxidized from hypophosphite after plating and discharged as waste, so methods to recycle and reuse phosphite should also be developed. Currently, there is no evidence of phosphite utilization by photosynthetic eukaryotes, including eukaryotic algae. Thus, except for the possible utilization by some bacteria when phosphate is unavailable, the fate of the phosphite that is discharged is mostly unknown. Chlorella vulgaris (NIES-2170), Coccomyxa subellipsoidea (NIES-2166), Scenedesmus obliquus (NIES-2280), and Botryococcus braunii (BOT-22) were cultured in phosphite medium under conditions that prevented phosphate contamination and phosphite oxidation. As a result, the number of C. vulgaris and C. subellipsoidea increased in the phosphite medium, demonstrating the availability of phosphite for the growth of these strains. In particular, the growth of C. vulgaris increased as the phosphite concentration increased. After being cultured for 180 days in photosynthetic conditions, phosphite utilization rates were 32–38%. In contrast, S. obliquus and B. braunii strains did not grow in the phosphite medium. In conclusion, C. subellipsoidea and C. vulgaris utilize phosphite as a P resource, which is a novel finding in photosynthetic eukaryotes. The results of this study may have important implications for the phosphorus redox cycle. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have high risks for human and living organisms due to their mutagenic and carcinogenic properties. Here, the effect of different concentrations of fluorene as a persistent toxic PAH on growth parameters and antioxidant systems in the green microalga Chlorella vulgaris was investigated. Intriguingly, cell number as well as dry and fresh weight of the alga were raised at 2 ppm fluorene compared to the control sample. However, with the increasing levels of fluorene from 10 to 50 mg L−1, the growth parameters gradually decreased. Accordingly, cells of C. vulgaris were found to enhance the activity of ROS scavenging enzymes after 7 days of exposure to fluorene in a concentration-dependent manner. Exposure to 25 and 50 mg L−1 fluorene was led to a significant decrease at chlorophyll content, whereas the concentration of carotenoids was not changed. Total phenol and flavonoid contents were markedly raised in 50 mg L−1 of fluorene compared to the control. Although flow cytometry assessment showed no substantial reduction in the viability at 50 mg L−1 fluorene-treated samples for 24 h, chlorophyll fluorescence was noticeably reduced. The results of SEM analysis revealed that the 50 mg L−1 fluorene treatment clearly damaged the algal cells after 24 h. The ability of the alga for biodegradation of fluorene was assessed by GC-MS. Consequently, a number of produced intermediate compounds were identified. These findings displayed that C. vulgaris had not only notable resistance against fluorene but also noteworthy potential for its degradation. [ABSTRACT FROM AUTHOR]

Microalgal lipids have been considered as one of the most promising feedstocks for biodiesel production. In order to solve the contradiction of algae growth and lipid accumulation, Chlorella vulgaris was co-cultured with Mesorhizobium sangaii under nitrogen deficiency conditions. The biomass and lipid production of C. vulgaris–bacteria co-culture with initial ratio of algae/bacteria = 40:1 were significantly improved compared with the pure algae culture. The maximum biomass, lipid content and productivity of algae in the co-cultures at 40:1 ratio were 1.89 mg L−1, 51.2%, and 96.77 mg L−1 day−1, respectively, which were 1.5, 2.2, and 3.3 times higher than those of the pure algae culture. Furthermore, the proportion of unsaturated fatty acids and C18:1 fatty acid of the consortium system was also significantly increased. Our study clearly suggests that co-cultivation of algae–bacteria can effectively contribute to the quality and quantity of microalgal bio-oil and shows promising applications for production of algal biomass and biodiesel. [ABSTRACT FROM AUTHOR]

Co-cultivation of microalgae and bacteria during municipal wastewater treatment can boost carbon and nutrient recovery as a result of their synergistic interactions. The symbiotic relationships between the locally isolated microalga Chlorella vulgaris and the bacterium Rhizobium sp., co-isolated from municipal wastewater, were investigated batchwise under photoautotrophic, heterotrophic, and mixotrophic conditions in a synthetic municipal wastewater medium. During photoautotrophic growth in BG11 medium, photosynthetic algal oxygenation and organic carbon production supported bacterial activity but no significant beneficial effects on microalgal growth were observed. In synthetic wastewater, a twofold higher biomass concentration was achieved in the axenic algal culture compared with the co-culture under heterotrophic conditions, suggesting a competition for nutrients. A comparable carbon removal was observed in all cultures (83–79% TOC), but a faster nitrogen consumption (59% TN) and complete phosphate assimilation (100% TP) was only achieved in the co-culture. A positive synergistic relationship was found under mixotrophic conditions, clearly supported by an in situ O2/CO2 exchange between the microorganisms. This mutualism led to a threefold higher biomass production with a 13-fold higher fatty acid content compared with the axenic algal culture, as well as a superior wastewater treatment performance (+ 58% TOC, + 41% TN and + 44% TP). The co-cultivation of C. vulgaris and Rhizobium is therefore suggested as a potential microbial consortium for a cost-efficient biomass generation during municipal wastewater reclamation, especially under mixotrophic conditions. [ABSTRACT FROM AUTHOR]

Fatty acid production from Chlorella vulgaris under nitrogen starvation in autotrophic, heterotrophic, and mixotrophic cultures was investigated and compared in this study. Both the biomass and fatty acid productivities of mixotrophic algal cells exceed the combination of autotrophic and heterotrophic cells when acetate was adopted as the organic carbon source, and fatty acid productivity from mixotrophic culture (130 mg L−1 day−1) is 1.9 times greater than the combination of autotrophic (15 mg L−1 day−1) and heterotrophic (51 mg L−1 day−1) cultures. C18:1 is the predominant fatty acid accounting for 60.4 and 64.5% of the total fatty acids in the mixotrophic and heterotrophic cultures, respectively. Moreover, the fatty acid yield from mixotrophic culture is almost two times greater than from heterotrophic culture. Proteomic analysis revealed that the activity of the tricarboxylic acid (TCA) cycle is improved in mixotrophic culture when compared with heterotrophic culture, leading to more fatty acid synthesis in C. vulgaris. [ABSTRACT FROM AUTHOR]

Efficient provision of carbon dioxide to microalgae is one of the major challenges to cost-effective large-scale cultivation. Previously, we have demonstrated the effectiveness of a novel membrane system in delivering CO2 to a marine strain of Chlorella sp. from CO2-loaded solvents. In this approach, the solvent is pumped through a non-porous hollow fibre membrane immersed in a microalgae medium, allowing passive transfer of CO2 that is utilised by the microalgae to enhance their growth, while simultaneously regenerating the solvent. In this article, we compare the growth of both fresh water and marine strains of algae using this membrane delivery system. While the fresh water medium has less pH buffering capacity and can dissolve less CO2, it proves similarly effective in delivering CO2 to the growing algae. Both the freshwater and marine species of Chlorella have slightly higher growth rates than the other species tested—Dunaliella tertiolecta and Haematococcus pluvialis. However, due to the lower osmotic pressure of the fresh water medium, more water is drawn through the membrane into the solvent than when the salt water medium is used. In conclusion, while CO2 delivery through the membrane system is effective for both salt and fresh water media, better performance is obtained for the salt water medium. [ABSTRACT FROM AUTHOR]

Hydroponic growing systems and the application of natural biostimulant substances are becoming very attractive option for crop cultivation due to their economic relevance since they allow reduction in the use of fertilizer and increase the yield. In order to perform a hydroponic co-cultivation system of microalgae (Chlorella vulgaris or Scenedesmus quadricauda) and tomato plants, grown in Hoagland nutrient solution, their mutual effect and the influence of a natural biostimulant obtained by alkaline extraction from a digestate of agro-livestock residues (DHL) were evaluated. The results showed that the co-cultivation system positively affected the growth of both tomato plants and microalgae. The best option, aimed to a mutual benefit for both cultures, resulted to be the co-cultivation system of tomato plants and S. quadricauda in the presence of DHL, positively affecting the growth of tomato plants along with a great increase in microalgal biomass. [ABSTRACT FROM AUTHOR]

The radiative properties of microalgae (the absorption cross-section, scattering cross-section, and scattering phase function) are essential for analyzing the light transfer in photobioreactors (PBRs). Due to the growth of microalgal cells, their radiative properties will vary with time. However, the growth-dependent radiative properties of microalgal cells have been rarely considered in the literature in analyzing light fluence rate in the PBRs and its influence on the accuracy of light fluence rate prediction is not well evaluated. In this work, the growth-dependent radiative properties of Chlorella vulgaris are studied via a semi-analytical approach. The growth-dependent cell size distribution of C. vulgaris is taken from experimental data in the literature. The temporal evolution of the scattering and absorption cross-sections and scattering phase function of C. vulgaris is determined based on the Lorenz-Mie theory combined with the growth-dependent cell size distributions and pigment content. The relative deviation of the radiative properties of microalgae at different growth phase with that at stationary phase microalgae is investigated. The deviation of predicted light fluence rate in a flat-plate PBR using the growth-dependent radiative properties and the radiative properties at stationary phase is evaluated. The results show that the relative deviation of absorption, scattering, and extinction cross-sections is significant, especially at exponential growth phase (over 18%). The relative deviation of the predicted light fluence rate is over 40% at exponential growth phase. As a result, the growth-dependent radiative properties have to be applied in order to accurately predict the light fluence rate in PBRs during different growth phases. A simple model is presented and demonstrated good performance to predict the growth-dependent radiative properties of C. vulgaris over the whole growth phase. The presented analysis will facilitate the design and optimization of the optical configuration of PBRs for microalgal cultivation. [ABSTRACT FROM AUTHOR]

Efficient methodology for simultaneous extraction of multiple bioactive compounds from microalgae still remains a major challenge. The present study provides a method for the sequential production of three major products: Chlorella Growth Factor (CGF, a nucleotide-peptide complex enriched with vitamins, minerals, and carbohydrates), lipid, and carotenoids from Chlorella vulgaris biomass in an economically feasible manner. After protein-rich CGF was extracted, the spent biomass was found to contain 12% lipid and 3% carotenoids when extracted individually, compared to that of the un-utilized (fresh) biomass (lipid, 14%; carotenoids, 4%). When extracted simultaneously using conventional methods, the yield of lipid from “CGF and carotenoids-extracted biomass,” and carotenoids from “CGF and lipid-extracted biomass” were significantly reduced (50%). However, simultaneous extraction using different solvent mixtures such as hexane:methanol:water and pentane:methanol:water mixture-augmented lipid yield by 38.5% and carotenoids by 14%, and additionally retained chlorophyll and its derivatives. Column chromatographic approach yielded sequential production of lipid (18%), lutein (9%) with better yields as well as without chlorophyll interference. Different geometric isomers of lutein all-E-(trans)-(3R,3′R,6′R)-β,ε-carotene-3,3′diol, 9Z(cis)-(3R,3′R,6′R)-β,ε-carotene-3,3′diol, and 13Z(cis)-(3R,3′R,6′R)-β,ε-carotene-3,3′diol were purified by HPLC and elucidated by CD, UV, NMR, FT-IR, and Mass spectra. In conclusion, the study provides an efficient and economically viable methodology for sequential production of lipid and lutein along with its geometrical isomers without chlorophyll influence and yield loss from the protein-rich CGF-extracted spent biomass of marine microalga, Chlorella vulgaris. [ABSTRACT FROM AUTHOR]

Chlorella is a green unicellular alga that has a wide range of future biotechnical applications such as production of pharmaceuticals and biodiesel. Efficient genetic transformation of Chlorella vulgaris has been difficult due to technical limitations. In this study, an efficient and reliable transformation system of electroporation was established using two different reporter genes. First, C. vulgaris cell wall was digested with enzyme mixture for preparing protoplasts. The optimal transformation efficiency was 1.67 × 104 ± 0.083 cfu μg−1 plasmid under the following conditions: 2 × 106 cells mL−1 of growing culture; 655 V pulse voltage with 3.4 ms pulse width. After transformation, green and cyan fluorescence were observed from transgenic C. vulgaris harboring gfp (green fluorescent protein) gene of pCAMBIA1302 and cfp (cyan fluorescent protein) gene of pSK397, respectively, using laser confocal microscope. RT-PCR analysis as well as Southern blot confirmed the integration of reporter gene at the molecular level. This efficient transformation system of C. vulgaris would be valuable for the production of recombinant proteins in the future. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris Beijerinck is a spherical, green alga belonging to the genus Chlorella and family Chlorellaceae. It has high nutritional value and shows multiple biological effects. Dietary supplements that contain extracts of C. vulgaris are sold in the form of tablets, capsules, powders, and aqueous solutions. To the best of our knowledge, this is the first study to determine the content of bioelements (zinc, iron, and magnesium), phenolic compounds, and lutein before and after incubation with artificial digestive juices from preparations containing C. vulgaris. In this study, we used commercial preparations in the form of powder and tablets. The samples were incubated in artificial gastric juice and then in artificial intestinal juice for 30 and 90 min. The contents of bioelements were determined by using the flame atomic absorption spectrometric method. Lutein and phenolic compounds were analyzed by high-pressure liquid chromatography. We also aimed to evaluate the quality of chlorella-containing formulations by using the methods described in the European Pharmacopoeia 8th edition. According to the results, the preparations containing C. vulgaris demonstrated the presence of phenolic compounds and lutein. Therefore, daily supplementation of preparations containing C. vulgaris substantiates its usefulness for humans. The qualitative composition of the examined organic substances and bioelements was found to be in accordance with the manufacturer’s declarations on the packaging containing C. vulgaris compared with the control samples; however, the contents of bioelements were found to be negligible after incubation with artificial digestive juices. This shows that the examined preparations containing C. vulgaris are not good sources of bioelements such as zinc, iron, or magnesium. [ABSTRACT FROM AUTHOR]

Microalgae are photosynthetic organisms with the ability to produce a variety of high-value compounds such as polyunsaturated fatty acids (PUFAs), proteins, pigments, and lipids. The high cost of microalgae production is one of the biggest obstacles for their commercialization. Plant growth regulators might be an ideal choice since they could potentially induce microalgae to produce lipids and other high-value secondary metabolites thereby reducing production cost. This study investigated the effects of eight plant growth regulators (PGRs), namely, salicylic acid (SA); 1-naphthaleneacetic acid (NAA); gibberellin (GA3); 6-benzylaminopurine (6-BA); 2,4-epibrassinolide (EBR); abscisic acid (ABA); ethephon (ETH); and spermidine (SPD) on the induction of lipids, proteins, carotenoids, and unsaturated fatty acids (UFAs) in Chlorella vulgaris. Moreover, the expression profiles of seven fatty acid biosynthethis genes were studied in the PGR-treated biomass. All PGRs used in the study caused significant increases in total lipid contents in non-dose-dependent manners when compared to control. However, lipid productivities were increased due to four of the eight PGRs (ABA, 6-BA, NAA, and ETH). Similar to lipids, total carotenoid contents were significantly higher in all of the PGR-treated microalgal biomass except ABA. However, soluble protein contents were not affected by the PGR treatments except SA at 10 mg L−1. Furthermore, 6-BA, NAA, ABA, and ETH treatments resulted in significant increases in UFAs especially DHA, linolenic acid, arachidonic acid, and EPA which were confirmed by the upregulation of fatty acid biosynthesis genes including stearoyl-ACP-desaturase, ω-3 fatty acid desaturase, biotin carboxylase, and acyl-acyl carrier protein. Our findings, therefore, indicate that the treatment with PGR used in this study could be a useful tool to produce biodiesel and other high-value metabolites from microalgal biomass. [ABSTRACT FROM AUTHOR]

The photoautotrophic co-culture of Chlorella vulgaris and the yeast Rhodotorula glutinis (MP culture) from industrial wastewater was investigated. Cell numbers, biomass, lipid production, and fatty acid content were measured. Owing to co-culture interaction with yeast and microalgae, the MP culture resulted in the highest number of cells (27.73 × 10 cells mL) and biomass (0.808 g L). Lipid production in the MP culture (117.73 mg L) was fourfold higher than that in the photoautotrophic pure culture (23.1 mg L). The content of palmitic acid (C16:0) was 24.65%, whereas that of oleic acid (C18:1) was 56.34% in the MP culture, which was higher than in other cultures. The results of this study indicate that MP cultures can be used to effectively support the growth of microorganisms and as an approach for biodiesel production. [ABSTRACT FROM AUTHOR]

Sodium erythorbate (NaE) is a common antioxidant in food processing. In this study, the abilities of NaE to reduce photosynthetic oxygen accumulation in culture medium and improve microalgal growth were evaluated using the green microalga Chlorella vulgaris and glucose as a reference. NaE (from 2.0 to 16.0 g L) led to a lower accumulation of dissolved oxygen (DO) in a concentration-dependent manner. A significant negative correlation ( p < 0.05) between the optical density (OD) and DO level suggested that algal growth was promoted by NaE through depleting oxygen in the medium. After 12 days of cultivation, maximum OD and biomass were obtained with a NaE dosage of 8.0 g L (respectively, 3.99 and 6.26 times greater than in the control without NaE). Compared with this dosage group which maintained an appropriate low DO level (2 to 6 mg L), higher dosage groups showed relatively little growth promotion due to an insufficiency of DO (<2 mg L). When glucose was added into mixotrophic systems for C. vulgaris, to the same total carbon amount as NaE, DO fell rapidly to less than 2 mg L owing to its greater consumption (43.9%) compared to that of NaE (16.7%). Furthermore, in the NaE treatment, the pigment contents, cell density, and algal biomass were, respectively, 4.17 to 4.44 times, 2.67 times, and 1.21 times greater than in the glucose treatment. These findings indicate that algal autotrophic growth could be enhanced effectively by NaE through the moderate control of DO. [ABSTRACT FROM AUTHOR]

Microalgae are rich resources for high-value nutrients and biodiesel production. However, extraction of these valuable compounds from them requires costly energy-consuming procedures due to their rigid cell walls. Application of cell-disruptive agents, the AES-Bt agents, extracted from an algicidal bacterium, Bacillus thuringiensis ITRI-G1, are a promising way to reduce the cost of cell disruption. Treatment with AES-Bt agents resulted in a rapid decline of photosynthesis ability and caused cell death in Chlorella vulgaris. Hallmarks of programmed cell death (PCD), including chromatin condensation, DNA fragmentation, and phosphatidylserine externalization, were detected in C. vulgaris cells treated with the AES-Bt agents. Therefore, the cell disruption effect caused by application of the AES-Bt agents can be due to the occurrence of PCD. Similar to other PCDs, the PCD caused by AES-Bt agents was also associated with increased reactive oxygen species (ROS). However, co-treatments with diphenyleneiodonium chloride (DPI), an NAD(P)H oxidase inhibitor, or N, N′-dimethylthiourea (DMTU), a hydrogen peroxide (HO) trap, with the AES-Bt agents successfully reduced ROS production, and more cells displayed a feature of PCD detected after the co-treatments. In conclusion, the AES-Bt agents can promote PCD of microalgae; however, the mechanism may not be through induction of ROS. [ABSTRACT FROM AUTHOR]

In this study, an alga-based simultaneous process of treating swine wastewater (SWW) and producing biodiesel was explored. Chlorella vulgaris (UTEX-265) was employed as a model species, and a SWW-based medium was prepared by dilution with tap water. Chlorella vulgaris grew well in the SWW-based medium, and at optimum dilution ratios, it exceeded the conventional culture medium in terms of biomass concentration and productivity. In eightfold diluted SWW, which supported the maximum growth, biomass productivity was 0.247 g L day, while the productivity was merely 0.165 g L day in standard tris-acetate-phosphorous (TAP) algal medium. In addition, fatty acid methyl ester (FAME) productivity was greater in the SWW-based medium (0.067 versus 0.058 g L day). This enhanced productivity resulted in more than 95 % removal of both nitrogen and phosphorous. All these show that C. vulgaris cultivation is indeed possible in a nutrient-rich wastewater with appropriate dilution, and in so doing, the wastewater can effectively be treated. [ABSTRACT FROM AUTHOR]

The use of microalgae in biological wastewater treatment has been widely studied. However, there is a dearth of information about estimating the microalgae and bacteria concentrations. In order to maintain a stable algal-bacterial system, it is necessary to quantify both the algal and bacterial biomasses. Typically, microalgae and bacteria from flocs in activated sludge contribute to better biomass settleability. However, flocs cause problems when it comes to estimating the individual biomass concentrations of microalgae and bacteria in a symbiotic algae-bacteria aggregate. This study aimed to find the best disintegration treatment with low influence on the viability of the microalgal cell determined by its photosynthetic activity. In the present work, biological (enzyme solution), chemical (formaldehyde), mechanical (glass bead-beating), and physical (sonication) treatments were performed on microalgae-bacteria flocs (ALBA flocs) to disintegrate the community as a pre-treatment step in order to develop a method for estimating the algal and bacterial concentration and to quantify the degree of disintegration. The effectiveness of the methods to disintegrate ALBA flocs in descending order are the following: sonication, bead-beating, formaldehyde and enzyme application. Sonication treatment (40 W, 6 min) showed the best disintegration performance of the microalgal-bacterial flocs, up to 90 % with 17 % loss of the algal photosynthetic activity. Bead-beating (3 mm diameter, 80 s) achieved 80 % of disintegration with only 6 % loss of its photosynthetic activity. These results demonstrate the possibility of mild disintegration of compact ALBA flocs without having any adverse impact on the microalgae cell. After these treatments, it becomes possible to estimate the individual biomass concentrations of algae and bacteria manually such as with a cell-counting chamber. [ABSTRACT FROM AUTHOR]