Optimal growth conditions to enhance Chlorella vulgaris biomass production in indoor phyto tank and quality assessment of feed and culture stock.

Commercial microalgae cultivation is a dynamic field with ongoing efforts to improve efficiency, reduce costs, and explore new applications. We conducted a study to examine how different light exposure periods affect Chlorella vulgaris's growth. We employed a Phyto tank batch system of approximately 3.5 L with LED light control, controlled airflow, and sterilized bags, maintained at 22.0 ± 2.0 °C indoors. Various methods, including spectrophotometry, and cell counter were employed to monitor Chlorella vulgaris growth under different light exposure cycles. Additionally, quality analysis as feed source was employed by proximate, amino acid, beta-glucan, and microbial content analysis. The results revealed significant variations in C. vulgaris biomass production based on light exposure duration. Notably, the 16:8-h light-dark photoperiod exhibited the highest biomass concentration, reaching 6.48 × 107 ± 0.50 cells/mL with an optical density (OD) of 1.165 absorbance at 682 nm. The 12:12-h light-dark photoperiod produced the second-highest biomass concentration, with 2.305 × 106 ± 0.60 cells/mL at an OD of 0.489. Proximate analysis of dry algae powder revealed low lipid content (0.48 %), high protein content (37.61 %), variable ash concentration (average 10.75 %), and a significant carbohydrate fraction (51.16 %) during extended daylight and shorter dark periods. Amino acid analysis identified nine essential amino acids, with glutamic acid being the most abundant (17.7 %) and methionine the least (0.4 %). Furthermore, quality analysis and microbiological assays demonstrated that the C. vulgaris biomass is well-suited for fish and livestock use as a feed source and possibility as human nutraceuticals. These findings can be considered more environmentally friendly and ethically sound due to the absence of genetic modification.

Analyzing the Impact of Physicochemical Factors on Chlorella vulgaris Growth Through Design of Experiment (DoE) for Carbon Capture System.

The CO2 emission is increasing every year and threatening both humans and the ecosystem. Carbon capture technological innovations have emerged as a potential solution to mitigate this emissions. Due to its high capacity of photosynthetic activity, CO2 sequestration by microalgae, such as Chlorella vulgaris has attracted much attention as a carbon capture system. The growth of this microalgae is influenced by various physicochemical factors. By designing the Design of Experiment (DoE) with Response Surface Methodology (RSM), the effect of several independent factor can be evaluated to optimize Chlorella vulgaris growth condition and CO2 conversion. This study aims to identify the most impact factors affecting C. vulgaris growth through investigating the variations in physicochemical factors of aeration, initial pH, dark light regime, saline, and substrates concentration using DoE. In this study, C. vulgaris was cultivated in batch culture for 10 days with 8 experiments that were designed under various conditions as per experimental run. Biomass growth was observed using optical density and analyzed by first order regression. The result shows that aeration parameters was statistically significant affect microalgae growth, evidence by p-value below 0.05 at all observation points. Runs with aeration treatment showed a prolonged exponential growth phase and delayed onset of the deceleration phase. Additionally, this study also found that the initial pH level also significantly affects growth at the last day of cultivation. Cultures with a higher initial pH reached the stationary phase earlier than those with a lower pH. Thus, the growth of C. vulgaris can be optimized by adding aeration treatment into culture media and regulating initial pH around 8 to enhancing carbon fixation and biomass yield.

Exploiting Potential Probiotic Lactic Acid Bacteria Isolated from Chlorella vulgaris Photobioreactors as Promising Vitamin B12 Producers.

Lactic acid bacteria (LAB) have been documented as potential vitamin B12 producers and may constitute an exogenous source of cobalamin for the microalga Chlorella vulgaris, which has been described as being able to perform vitamin uptake. Hence, there is an interest in discovering novel B12-producing probiotic LAB. Therefore, the purpose of the current work was to perform a phenotype-genotype analysis of the vitamin B12 biosynthesis capacity of LAB isolated from C. vulgaris bioreactors, and investigate their probiotic potential. Among the selected strains, Lactococcus lactis E32, Levilactobacillus brevis G31, and Pediococcus pentosaceus L51 demonstrated vitamin B12 biosynthesis capacity, with the latter producing the highest (28.19 ± 2.27 pg mL-1). The genomic analysis confirmed the presence of pivotal genes involved in different steps of the biosynthetic pathway (hemL, cbiT, cobC, and cobD). Notably, P. pentosaceus L51 was the only strain harboring cobA, pduU, and pduV genes, which may provide evidence for the presence of the cobalamin operon. All strains demonstrated the capability to withstand harsh gastrointestinal conditions, although P. pentosaceus L51 was more resilient. The potential for de novo cobalamin biosynthesis and remarkable probiotic features highlighted that P. pentosaceus L51 may be considered the most promising candidate strain for developing high-content vitamin B12 formulations.

Dietary Supplementation of Chlorella vulgaris Effectively Enhanced the Intestinal Antioxidant Capacity and Immune Status of Micropterus salmoides.

An M. salmoides fish meal diet was supplemented with 0 (CHL0, Control), 38 (CHL38), 76 (CHL76), 114 (CHL114), and 152 (CHL152) mg/kg C. vulgaris for 60 days, and their serum and intestinal samples were analyzed. The results showed that the albumin (ALB) and total protein (TP) contents were observably enhanced in the CHL76 group compared with the Control group. The intestinal glutathione (GSH) and glutathione peroxidase (GSH-Px) contents were enhanced significantly in the CHL76 group, while the total antioxidant capacity (T-AOC) was enhanced in the CHL38 group, compared with the Control group. However, supplementation of >76 g/kg C. vulgaris significantly inhibited the superoxide dismutase (SOD) activity in the intestines of M. salmoides. Moreover, the malondialdehyde (MDA) content was observably dropped in the CHL-supplemented groups compared with the Control group. Transcriptome analysis of the CHL76 and Control groups displayed a total of 1384 differentially expressed genes (DEGs). KEGG analysis revealed that these DEGs were enriched in apoptosis, cytokine-cytokine receptor interaction, tight junction (TJ), and phagosome signaling pathways, which were associated with improved intestinal immunity in the CHL76 group. Additionally, the DEGs enriched in the above pathways were also correlated with the antioxidant parameters, such as catalase (CAT), GSH, GSH-Px, SOD, T-AOC, and MDA. Therefore, our study found that dietary supplementation of C. vulgaris effectively enhanced the intestinal antioxidant capacity of M. salmoides by increasing antioxidant enzyme activity and decreasing MDA content. Additionally, dietary supplementation of C. vulgaris improved the intestinal immune status of M. salmoides by reducing proapoptotic and proinflammatory factors, increasing intestinal TJs- and phagosome-related genes expressions, and increasing the serum ALB and TP contents. Lastly, quadratic regression analysis of the serum biochemical indices (ALB and TP) and intestinal antioxidant parameters (GSH-Px and GSH) revealed that the optimal supplemental level of C. vulgaris in the M. salmoides diet was 58.25-77.7 g/kg.

Not so dangerous? PET microplastics toxicity on freshwater microalgae and cyanobacteria.

Microalgae and cyanobacteria are among the most important primary producers and are responsible for the production of 50-80% of the oxygen on Earth. They can be significantly affected by plastic pollution, as the vast majority of plastic waste ends up in rivers and then the oceans. This research focuses on green microalgae Chlorella vulgaris (C. vulgaris), Chlamydomonas reinhardtii (C. reinhardtii), filamentous cyanobacterium Limnospira (Arthrospira) maxima (L.(A.) maxima) and how they are affected by environmentally relevant PET-MPs (polyethylene-terephtalate microplastics). Manufactured PET-MPs have asymmetric shape, size between 3 and 7 µm and were used in concentrations ranging from 5 mg/L to 80 mg/L. The highest inhibitory rate of growth was found in C. reinhardtii (-24%). Concentration-dependent changes in chlorophyll a composition were found in C. vulgaris and C. reinhardtii, not in L. (A.) maxima. Furthermore, cell damage was detected in all three organisms by CRYO-SEM (shriveling, cell wall disruption), but the cyanobacterium was the least damaged. A PET-fingerprint was detected on the surface of all tested organisms using FTIR, indicating the adherence of PET-MPs. The highest rate of PET-MPs adsorption was detected in L. (A.) maxima. Specifically, characteristic spectra were observed at ∼721, 850, 1100, 1275, 1342, and 1715 cm-1 which are specific for functional groups of PET-MPs. Nitrogen and carbon content significantly increased in L. (A.) maxima under exposure to 80 mg/L due to the PET-MPs adherence and mechanical stress. In all three tested organisms, weak exposure-related ROS generation was detected. In general, cyanobacteria seem to be more resistant to the effects of MPs. However, organisms in the aquatic environment are exposed to MPs over a longer time scale, so it is important to use the present findings for further longer-term experiments on environmentally relevant organisms.

Extraction of Bioactive Compounds from C. vulgaris Biomass Using Deep Eutectic Solvents.

C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio were used for that purpose. The extracts' total carotenoid (TCC) and phenolic contents (TPC), as well as their antioxidant activity (IC50), were determined within the process of identification of the most efficient solvent. This screening procedure revealed ChCl:1,2 butanediol (1:4)/H2O 70/30 w/w as the most compelling solvent; thus, it was employed thereafter for the extraction process optimization. Three extraction parameters, i.e., solvent-to-biomass ratio, temperature, and time were studied regarding their impact on the extract's TCC, TPC, and IC50. For the experimental design and process optimization, the statistical tool Response Surface Methodology was used. The resulting models' predictive capacity was confirmed experimentally by carrying out two additional extractions under conditions different from the experimental design.

Assessing OBT formation and enrichment: ROS signaling is involved in the radiation hormesis induced by tritium exposure in algae.

Tritium is the main component of radioactive wastewater from nuclear power plants and can be migrated into organisms to form organically bound tritium (OBT), which may pose a potential risk to aquatic ecosystem. Hence, it is essential to monitor OBT conversion in the presence of tritium exposure. In this study, the effects of pretreatment methods such as digestion on the recovery of tritium were discussed. It was found that microwave digestion pretreatment could improve the recovery of tritium by up to 90 % and allow OBT measurement with a small sample size equivalent to about 60 mg (dry weight). In addition, the efficiency of OBT transformation was different among biological samples, and the radiation hormesis phenomenon was induced by tritium exposure (3.7 × 106 Bq/L) in microalgae Chlorella vulgaris（C. vulgaris）. The tritium exposure may induce radiation hormesis through the reactive oxygen species (ROS) signaling pathway, thus improving the photosynthetic capacity and metabolism level of C. vulgaris. Furthermore, enhancement of photorespiration metabolism and the antioxidation system may be important means for C. vulgaris to balance damage by tritium radiation. This study provides insights for further investigating OBT behavior, and will contribute to understanding the equilibrium damage mechanism of algae exposed to tritium.

Determining biota succession in a domestic wastewater pond system after treatment with a specific consortium microalgae.

Wastewater stabilization ponds (WSPs) rely on the metabolic activities of the inhabiting microbiota to treat wastewater. A selected consortium of Chlorella vulgaris and Chlorella protothecoides were used to manipulate the natural resident microalgae assemblage to improve the treatment performance of a domestic wastewater pond treatment system in a coastal region. Since information is lacking about the resulting influence on the composition or succession of the phytoplankton or associated microbiota assemblage, the current study aimed to determine how dosing with the microalgae C. vulgaris and C. protothecoides change the efficiency of wastewater effluent treatment, as well as the composition and succession of the natural occurring phytoplankton and microbial assemblage throughout WSP system. After a year of specific microalgae inoculations, the effluent in part complied with the standards set by the Department of Water Affairs and Forestry (DWAF) and the USA, Environmental Protection Agency (EPA). The cyanobacteria Microcystis aeruginosa dominated the sixth (75%) and seventh pond (97%) before the inoculation with C. vulgaris and C. protothecoide commenced. After 12 inoculation events C. vulgaris and C. protothecoides were dominant in ponds three to seven while the dominant microbial groups were Bacteroidetes, Cyanobacteria, Firmicutes, Planctomycetes, Proteobacteria, Spirochaetes, Synergistetes and Verrucomicrobia. After the microalgae treatment, the WSP effluent were more compliant regarding to the set guidelines for effluent than prior to microalgae treatment. Based on the ability of the C. vulgaris and C. protothecoides to improve the effluent water quality, it was evident that the consortium of microalgae can be use improve domestic wastewater effluent in rural nutrient sensitive catchments. Supplementary Information: The online version contains supplementary material available at 10.1007/s40201-022-00840-z.

Direct toxicity of the herbicide florasulam against Chlorella vulgaris: An integrated physiological and metabolomic analysis.

Herbicides are the agents of choice for use in weed control; however, they can enter the aquatic environment, with potentially serious consequences for non-target organisms. Despite the possible deleterious effects, little information is available regarding the ecotoxicity of the herbicide florasulam toward aquatic organisms. Accordingly, in this study, we investigated the toxic effect of florasulam on the freshwater microalga Chlorella vulgaris and sought to identify the underlying mechanisms. For this, we employed a growth inhibition toxicity test, and then assessed the changes in physiological and metabolomic parameters, including photosynthetic pigment content, antioxidant system, intracellular structure and complexity, and metabolite levels. The results showed that treatment with florasulam for 96 h at the concentration of 2 mg/L, 2.84 mg/L, and 6 mg/L in medium significantly inhibited algal growth and photosynthetic pigment content. Moreover, the levels of reactive oxygen species were also increased, resulting in oxidative damage and the upregulation of the activities of several antioxidant enzymes. Transmission electron microscopic and flow cytometric analysis further demonstrated that exposure to florasulam (6 mg/L) for 96 h disrupted the cell structure of C. vulgaris, characterized by the loss of cell membrane integrity and alterations in cell morphology. Changes in amino acid metabolism, carbohydrate metabolism, and the antioxidant system were also observed and contributed to the suppressive effect of florasulam on the growth of this microalga. Our findings regarding the potential risks of florasulam in aquatic ecosystems provide a reference for the safe application of this herbicide in the environment.

Antifungal potential, chemical composition of Chlorella vulgaris and SEM analysis of morphological changes in Fusarium oxysporum.

In pursuit of an environmentally benign fungicide alternative, the current study explored the antifungal activity of Chlorella vulgaris extracts against six plant pathogenic fungi (in vitro). The well diffusion agar method was used to investigate the growth inhibition of Fusarium oxysporum, Fusarium sp., Fusarium solani, A. flavus, A. niger, and A. alternata using the three C. vulgaris extracts viz. methanol (CvME), acetone (CvAE), and diethyl ether (CvDE). Different concentrations of CvDE were also investigated against F. oxysporum. The morphological modifications in F. oxysporum treated with CvDE (5 mg/kg) were studied using SEM and the chemical composition of CvDE was also determined by GC-MS analysis. All extracts, with the exception of A. alternata, were found to be effective in inhibiting the growth of plant pathogenic fungi. The CvDE extract, followed by CvME and CvAE, was found to be efficient against tested fungi. The CvDE was most effective against F. oxysporum with a 73.3% growth inhibition. The effects of various CvDE concentrations on F. oxysporum were found to be dosage dependent. The SEM micrograph revealed that CvDE-treated F. oxysporum had substantially less conidia than the control. The CvDE treatment damaged the mycelial structure as well. Major chemical components detected in CvDE were Heptaldehyde (15.7%), Octadecenoic acid, methyl ester (12.6%), Hexadecanoic acid (12%), 3-Decyn-2-Ol (10.98%), (E)-3,7,11,15-tetramethylhexadec-2-ene (9.76%), heptadecane-1,2,3,4,5-pentol (8.7%), Docosane, 4-methyl (7.28%).

Phycoremediation of milk processing wastewater and lipid-rich biomass production using Chlorella vulgaris under continuous batch system.

This study compiles the results of phycoremediation of milk processing wastewater (MPWW) and production of lipid-rich Chlorella vulgaris biomass using a continuous batch system operated for 12-wks. After a 4-wks interval, a new MPWW was loaded photobioreactor to provide appropriate nutrient supply to algae. Results indicated that MPWW supported the algal growth efficiently and the maximum algal growth was recorded in the ranges of 400.36 to 421.58 mg L-1 during 4-wk's of the cultivation cycle. Average reduction in total nitrogen, TN (45.82-69.18%); nitrate, NO3 (93.32-94.54%); total ammonium nitrogen, TAN (92.94-94.54%); sulphate, SO4-2 (85.13-87.34%); total phosphorus (75.09-78.78%); and biochemical oxygen demands, BOD (89.53-92.40%) was recorded during 12-wks phycoremediation of MPWW. Harvested algal biomass (dry weight basis, DW) exhibited a significant content of total sugar (45.5%) and total lipid (39.7%). The lipid profiling results indicated the presence of palmitic acid (39.9%), oleic acid (21.08%), linoleic acid (13.13%), and other C18 compounds in algal biomass, suggesting the suitability of MPWW for Chlorella vulgaris cultivations. Algal biomass exhibited a high heating value (MJ/Kg of DW) in the range of 17.3 to 25.1, comparable to other lignocellulose biomass to be used for bioenergy purposes. Results of this study indicate that MPWW could be utilized as a valuable medium for Chlorella vulgaris cultivation under a circular economy approach: wastewater treatment and bioenergy feedstock production. The effect of controlled environmental conditions on algal growth behavior and lipid composition in biomass, while using MPWW as a medium, could be investigated in future studies.

Simultaneous nutrient recovery and algal biomass production from anaerobically digested sludge centrate using a membrane photobioreactor.

This study aims to evaluate the performance of C. vulgaris microalgae to simultaneously recover nutrients from sludge centrate and produce biomass in a membrane photobioreactor (MPR). Microalgae growth and nutrient removal were evaluated at two different nutrient loading rates (sludge centrate). The results show that C. vulgaris microalgae could thrive in sludge centrate. Nutrient loading has an indiscernible impact on biomass growth and a notable impact on nutrient removal efficiency. Nutrient removal increased as the nutrient loading rate decreased and hydraulic retention time increased. There was no membrane fouling observed in the MPR and the membrane water flux was fully restored by backwashing using only water. However, the membrane permeability varies with the hydraulic retention time (HRT) and biomass concentration in the reactor. Longer HRT offers higher permeability. Therefore, it is recommended to operate the MPR system in lower HRT to improve the membrane resistance and energy consumption.

Chlorella vulgaris meets TiO2 NPs: Effective sorbent/photocatalytic hybrid materials for water treatment application.

A new class of bio-nano hybrid catalyst useable in downstream wastewater treatment was developed. We combined the sorption potentialities of Chlorella vulgaris microalgae with the photocatalytic properties of TiO2 NPs in order to investigate unexplored synergistic effects that could push the algal remediation technology toward a more promising cost-effective balance. We exploited non-living C. vulgaris, which keeps the biosorption properties of the living microalgae, but greatly enhancing the overall processability. C. vulgaris biomass was coupled with TiO2 NPs and the nanosols were then dried by means of a spray freeze drying (SFD) process able to produce highly reactive granules. A widespread physicochemical characterization supported the preparation and the performance evaluation, so highlighting the key-role of C. vulgaris/TiO2 interaction at the colloidal state. Heavy metal adsorption, tested for copper ions, and photocatalytic activity, assessed for Rhodamine B (RhB) photodegradation, were evaluated as key performances. The results pointed out a positive synergistic effect for hybrid samples consistent with the enhancement of metal biosorption which ranges from 103 mg g-1, for pristine C. vulgaris, to about 4000 mg g-1, when the biomass was coupled with the inorganic nanophase. The photocatalytic activity was well preserved with a complete RhB conversion after 1 h and even advanced in presence of SiO2NPs into the inorganic counterpart, so increasing the kinetic constant from 8.70 to 10.7 10-2 min-1. The results pave the way for the integration of these sorbent/photocatalytic hybrid materials into water remediation systems in an innovative sustainable design perspective.

Revealing dual roles of g-C3N4 in Chlorella vulgaris cultivation.

Booming graphitic carbon nitride (g-C3N4) photocatalyzed water splitting increases crisis of aquatic contamination. However, a controversial understanding regarding effect of g-C3N4 on growth of microalgae still exists. Accordingly, Chlorella vulgaris were cultured in 0-250 mg/L of g-C3N4 with biomass named as C-0, C-50, C-100, C-150, C-200, and C-250, respectively. g-C3N4 below 200 mg/L was beneficial to short-term cultivation of microalgae, while it was harmful to long-time cultivation. Protein factions of C-0, C-100, and C-250 were 41.4, 42.3, and 36.4 wt%, while their lipid factions varied from 21.5, 16.9, to 17.8 wt%, respectively. In short-term cultivation, superoxide dismutase's activity of C-0, C-150, and C-250 increased dramatically, while accumulated H2O2 led to increased activity of catalase. However, it started to decrease once antioxidant enzymes were per-oxidized, leading to increase of malondialdehyde content. In long-term cultivation, activities of superoxide dismutase, catalase and malondialdehyde content decreased dramatically owning to peroxidation of algae. Scavenger tests with tertiary butanol and triethanolamine implied that·OH was dominate parameter affecting growth of microalgae. This work indicates that g-C3N4 below 200 mg/L is propitious to short-term cultivation of microalgae, while it is bad to long-time cultivation of microalgae, revealing dual rules of g-C3N4 in Chlorella vulgaris cultivation.

Preparation of the Enzymatic Hydrolysates from Chlorella vulgaris Protein and Assessment of Their Antioxidant Potential Using Caenorhabditis elegans.

This study aimed to assess the antioxidant potential of Chlorella vulgaris protein-derived enzymatic hydrolysate using Caenorhabditis elegans. Protein extraction was performed using an alkali solution after complete C. vulgaris swelling and hydrolysis using four commercial proteases (alcalase, neutrase, protamex, and flavourzyme). The results showed that the flavourzyme hydrolysates exhibited the strongest antioxidant activity both in vitro and in vivo. Under the optimum conditions of the enzymatic hydrolysis, the half-maximal effective concentration of the hydrolysates for superoxide and hydroxyl radicals was 0.323 mg/mL and 0.139 mg/mL, respectively. The hydrolysates could significantly extend the lifespan, improve the resistance to methyl viologen-induced oxidative stress, reduce the levels of reactive oxygen species, and enhance the activity of catalase and superoxide dismutase in C. elegans.

Toxic effect of fluorene-9-bisphenol to green algae Chlorella vulgaris and its metabolic fate.

Fluorene-9-bisphenol (BHPF), a bisphenol A (BPA) alternative, has recently attracted attention due to its wide use and potential toxicity. However, the toxic effects and fate of BHPF in freshwater algae remains to be elucidated. In this study, the impact of BHPF on Chlorella vulgaris was explored and the removal and bioaccumulation of BHPF by Chlorella vulgaris were investigated. Results showed that C. vulgaris was sensitive to BHPF at the concentration of >1 mg L-1, and lipid peroxidation was significantly increased under the exposure of >0.1 mg BHPF L-1. An oxidative stress was caused by BHPF, as the activities of superoxide dismutase (SOD) were significantly decreased in algal cells by >0.5 mg BHPF L-1. The removal rate of BHPF was significantly enhanced by the addition of algae. In addition, the increasing accumulation of BHPF in algae at concentrations ranging from 0.5 to 5 mg L-1 was observed and may contribute for the increased toxicity of BHPF to C. vulgaris. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) results demonstrated that three metabolites of BHPF were identified in algal cells, which may pose an unexpected effect in aquatic environment.

Chlorella vulgaris or Spirulina platensis mitigate lead acetate-induced testicular oxidative stress and apoptosis with regard to androgen receptor expression in rats.

The current research was constructed to throw the light on the protective possibility of Chlorella vulgaris (C. vulgaris) and Spirulina platensis (S. platensis) against lead acetate-promoted testicular dysfunction in male rats. Forty rats were classified into four groups: (i) control, (ii) rats received lead acetate (30 mg/kg bw), (iii) rats concomitantly received lead acetate and C. vulgaris (300 mg/kg bw), (vi) rats were simultaneously treated with lead acetate and S. platensis (300 mg/kg bw) via oral gavage for 8 weeks. Lead acetate promoted testicular injury as expressed with fall in reproductive organ weights and gonadosomatic index (GSI). Lead acetate disrupted spermatogenesis as indicated by sperm cell count reduction and increased sperm malformation percentage. Lead acetate-deteriorated steroidogenesis is evoked by minimized serum testosterone along with maximized follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels. Testicular oxidative, inflammatory, and apoptotic cascades are revealed by elevated acid phosphatase (ACP) and sorbitol dehydrogenase (SDH) serum leakage, declined testicular total antioxidative capacity (TAC) with elevated total oxidative capacity (TOC), tumor necrosis factor alpha (TNF-α), caspase-3 levels, lessened androgen receptor (AR) expression, and histopathological lesions against control. Our research highlights that C. vulgaris or S. platensis therapy can modulate lead acetate-promoted testicular dysfunction via their antioxidant activity as expressed by elevated TAC and reduced TOC, immunomodulatory effect as indicated by lessened TNF-α level, and anti-apoptotic potential that was revealed by minimized caspase-3 levels. As well as restoration of testicular histoarchitecture, androgen receptor, steroidogenesis, and spermatogenesis were detected with better impacts to S. platensis comparing with C. vulgaris. Therefore, further clinical trials are needed to test S. platensis and C. vulgaris as a promising candidate in treating male infertility.

Performance of a microalgal-bacterial consortium system for the treatment of dairy-derived liquid digestate and biomass production.

To enhance the treatment performance of dairy-derived liquid digestate (DLD) using microalgal-bacterial consortium system composed of Chlorella vulgaris and indigenous bacteria (CV), activated sludge was introduced to form a new microalgal-bacterial consortium system (Co-culture). The activated sludge shortened the lag phase and increased the specific growth rate of C. vulgaris (0.56 d-1). The biomass yield in the Co-culture was 2.72 g L-1, which was lower than that in the CV (3.24 g L-1), but the Co-culture had an improved COD (chemical oxygen demand) removal (25.26%) compared to the CV (13.59%). Quantitative PCR and metagenomic analyses demonstrated that microalgae also promoted bacterial growth, but influenced differently on the bacterial communities of indigenous bacteria and activated sludge. Compared with indigenous bacteria, activated sludge was more prone to forming a favorable symbiosis with C. vulgaris. These findings contribute to the construction of efficient microalgal-bacterial consortium system in wastewater treatment.

Chlorella vulgaris cultivation in airlift photobioreactor with transparent draft tube: effect of hydrodynamics, light and carbon dioxide on biochemical profile particularly ω-6/ω-3 fatty acid ratio.

Chlorella vulgaris is used for food and feed applications due to its nutraceutical, antioxidant and anticancer properties. An airlift photobioreactor comprising transparent draft tube was used for C. vulgaris cultivation. The effect of reactor parameters like hydrodynamics (0.3-1.5 vvm), light intensity (85-400 µmol m-2 s-1), photoperiod (12-24 h) and gas-phase carbon dioxide (CO2) concentration (5-15% v/v) were evaluated on microalgae and associated bacterial growth, biochemical profile; with special emphasis on ω-3, ω-6 fatty acids, and vitamin B12. The optimal growth of C. vulgaris without CO2 supplementation was observed at 1.2 vvm, which was associated with higher algal productivity, chlorophyll, vitamin B12 content, and bacterial load along with 72% of nitrate removal. The higher light intensity (400 µmol m-2 s-1) and photoperiod (24:0) increased biomass productivity and ω-3 fatty acid content (in lipid) up to 2-3 fold. The elevated levels of gas-phase CO2 concentration (15% v/v) enhanced EPA content up to 7% and biomass productivity up to 171 mg L-1 day-1. However, the increase in CO2 concentration lowered vitamin B12 content (up to 30%) and bacterial load (2-3 log). Also, all the cultivation conditions favoured desirable ω-6/ω-3 ratio(in the range of 1-2).

Removal of metronidazole from aqueous media by C. vulgaris.

This current study investigated the removal of metronidazole from aqueous media by C. vulgaris. Two different initial sizes of inoculum (0.05 and 0.5 g L-1) were tested for a wide concentration range of metronidazole (1-50 µM). The effect of metronidazole concentrations on biomass production was studied for 20 days. The exopolymeric substances (EPS) were quantified and correlated with the removal of antibiotics from aqueous media. Specifically, MDZ stimulated the production of EPS in C. vulgaris, which played the major role in the adsorption of this antibiotic. Also, metronidazole significantly influenced the zeta potential of C. vulgaris in the test cultures, indicating a change in surface characteristics. This decrease in surface negative charge caused auto-flocculation phenomena at a stationary phase. Chronic and acute toxicity experiments showed that metronidazole was harmful to C. vulgaris at stationary phase. Results from this study would advance our knowledge on the treatment of metronidazole-contaminated waters with C. vulgaris as a green technology-oriented process.