Nutrients recovery from dairy wastewater by Chlorella vulgaris and comparison of the lipid's composition with various chlorella strains for biodiesel production.

Microalgae biomass is regarded as a promising feedstock for biodiesel production. The biomass lipid content and fatty acids composition are among the main selective criteria when screening microalgae strains for biodiesel production. In this study, three strains of Chlorella microalgae (C. kessleri, C. sorokiniana, C. vulgaris) were cultivated nutrient media with different nitrogen contents, and on a medium with the addition of dairy wastewater. Moreover, microalgae grown on dairy wastewater allowed the removal of azote and phosphorous. The removal efficiency of 90%, 53% and 95% of ammonium nitrogen, total nitrogen and phosphate ions, respectively, were reached. The efficiency of wastewater treatment from inorganic carbon was 55%, while the maximum growth of biomass was achieved. All four samples of microalgae had a similar fatty acid profile. Palmitic acid (C16:0) was the most abundant saturated fatty acid (SFA), and is suitable for the production of biodiesel. The main unsaturated fatty acids (UFA) present in the samples were oleic acid (C18:1 n9); linoleic acid (C18:2 n6) and alpha-linolenic acid (C18:3 n3), which belong to omega-9, omega-6, omega-3, respectively.

Predicting the Structure of Enzymes with Metal Cofactors: The Example of [FeFe] Hydrogenases.

The advent of deep learning algorithms for protein folding opened a new era in the ability of predicting and optimizing the function of proteins once the sequence is known. The task is more intricate when cofactors like metal ions or small ligands are essential to functioning. In this case, the combined use of traditional simulation methods based on interatomic force fields and deep learning predictions is mandatory. We use the example of [FeFe] hydrogenases, enzymes of unicellular algae promising for biotechnology applications to illustrate this situation. [FeFe] hydrogenase is an iron-sulfur protein that catalyzes the chemical reduction of protons dissolved in liquid water into molecular hydrogen as a gas. Hydrogen production efficiency and cell sensitivity to dioxygen are important parameters to optimize the industrial applications of biological hydrogen production. Both parameters are related to the organization of iron-sulfur clusters within protein domains. In this work, we propose possible three-dimensional structures of Chlorella vulgaris 211/11P [FeFe] hydrogenase, the sequence of which was extracted from the recently published genome of the given strain. Initial structural models are built using: (i) the deep learning algorithm AlphaFold; (ii) the homology modeling server SwissModel; (iii) a manual construction based on the best known bacterial crystal structure. Missing iron-sulfur clusters are included and microsecond-long molecular dynamics of initial structures embedded into the water solution environment were performed. Multiple-walkers metadynamics was also used to enhance the sampling of structures encompassing both functional and non-functional organizations of iron-sulfur clusters. The resulting structural model provided by deep learning is consistent with functional [FeFe] hydrogenase characterized by peculiar interactions between cofactors and the protein matrix.

Impact of organic matter molecular weight on hexavalent chromium enrichment in green microalgae.

In lightly polluted water containing heavy metals, organic matter, and green microalgae, the molecular weight of organic matter may influence both the growth of green microalgae and the concentration of heavy metals. This study elucidates the effects and mechanisms by which different molecular weight fractions of fulvic acid (FA), a model dissolved organic matter component, facilitate the bioaccumulation of hexavalent chromium (Cr(VI)) in a typical green alga, Chlorella vulgaris. Findings show that the addition of FA fractions with molecular weights greater than 10 kDa significantly enhances the enrichment of total chromium and Cr(VI) in algal cells, reaching 21.58%-31.09 % and 16.17 %-22.63 %, respectively. Conversely, the efficiency of chromium enrichment in algal cells was found to decrease with decreasing molecular weight of FA. FA molecular weight within the range of 0.22 µm-30 kDa facilitated chromium enrichment primarily through the algal organic matter (AOM) pathway, with minor contributions from the algal cell proliferation and extracellular polymeric substances (EPS) pathways. However, with decreasing FA molecular weight, the AOM and EPS pathways become less prominent, whereas the algal cell proliferation pathway becomes dominant. These findings provide new insights into the mechanism of chromium enrichment in green algae enhanced by medium molecular weight FA.

Photoheterotroph improved the growth and nutrient levels of Chlorella vulgaris and the related molecular mechanism.

Microalgae are rich in fatty acids, proteins, and other nutrients, which have gained the general attention of researchers all over the world. For the development of Chlorella vulgaris in food and feed industry, this study was conducted to investigate the differences in C. vulgaris' growth and nutritional components under different culture conditions (autotrophic, heterotrophic, photoheterotrophic) and the internal factors through cell counting in combination with transcriptome and nutrient analyses. The results showed that, under the photoheterotrophic condition, Chlorella's growth and the contents of lipid and protein were significantly higher than that under the heterotrophic condition, and the moisture content was lower than that under the heterotrophic condition. The saturated fatty acid content under the photoheterotrophic condition was the lowest, while the polyunsaturated fatty acid content was significantly higher than those under the other two conditions. There were 46,583 differentially expressed genes (DEGs), including 33,039 up-regulated DEGs (70.93%) and 13,544 down-regulated DEGs (29.07%), under the photoheterotrophic condition in comparison with the autotrophic condition. The fold change between the two conditions of samples of up-regulated genes was higher than that of the down-regulated genes. The KEGG enrichment showed that the up-regulated DEGs in the photoheterotrophic condition were significantly enriched in 5 pathways, including protein processing in endoplasmic reticulum pathway, photosynthesis pathway, photosynthesis-antenna protein pathway, endocytosis pathway, and phosphonate and phosphinate metabolism pathway. DEGs related to fatty acid metabolic pathways were significantly enriched in the fatty acid biosynthesis pathway and the biosynthesis of unsaturated fatty acid pathway. The qPCR analysis showed that the expression pattern of the selected genes was consistent with that of transcriptome analysis. The results of this study lay a theoretical foundation for the large-scale production of Chlorella and its application in food, feed, and biodiesel. KEY POINTS: • Nutrient levels under photoheterotrophic condition were higher than other conditions. • Six important pathways were discovered that affect changes in nutritional composition. • Explored genes encode important enzymes in the differential metabolic pathways.

Emulgel based on fish skin collagen-microalgae-silver increased neovascularization and re-epithelialization of full thickness burn in rats.

Deep skin burn represents a global morbidity and mortality problem, and the limitation of topical treatment agents has motivated research to development new formulations capable of preventing infections and accelerating healing. The aim of this work was to develop and characterize an emulgel based on collagen (COL) and gelatin (GEL) extracted from fish skin associated with Chlorella vulgaris extract (CE) and silver nitrate (AgNO3). COL and GEL were characterized by physicochemical and thermal analyses; and CE by electrophoresis and its antioxidant capacity. Three emulgels formulations were developed: COL (0.5%) + GEL (2.5%) (E1), COL+GEL+CE (1%) (E2), and COL+GEL+CE + AgNO3 (0.1%) (E3). All formulations were characterized by physicochemical, rheology assays, and preclinical analyses: cytotoxicity (in vitro) and healing potential using a burn model in rats. COL and GEL showed typical physicochemical characteristics, and CE presented 1.3 mg/mL of proteins and antioxidant activity of 76%. Emulgels presented a coherent physicochemical profile and pseudoplastic behavior. Preclinical analysis showed concentration-dependent cytotoxicity against fibroblast and keratinocytes. In addition, all emulgels induced similar percentages of wound contraction and complete wound closure in 28 days. The histopathological analysis showed higher scores for polymorphonuclear cells to E1 and greater neovascularization and re-epithelialization to E3. Then, E3 formulation has potential to improve burn healing, although its use in a clinical setting requires further studies.

Interactions of monolayer molybdenum disulfide sheets with metalloid antimony in aquatic environment: Adsorption, transformation, and joint toxicity.

The tremendous application potentiality of transitional metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2) nanosheets, will unavoidably lead to increasing release into the environment, which could influence the fate and toxicity of co-existed contaminants. The present study discovered that 59.8 % of trivalent antimony [Sb(III)] was transformed by MoS2 to pentavalent Sb [Sb(V)] in aqueous solutions under light illumination, which was due to hole oxidation on the nanosheet surfaces. A synergistic toxicity between MoS2 and Sb(III, V) to algae (Chlorella vulgaris) was observed, as demonstrated by the lower median-effect concentrations of MoS2 + Sb(III)/Sb(V) (13.1 and 20.9 mg/L, respectively) than Sb(III)/Sb(V) (38.8 and 92.5 mg/L, respectively) alone. Particularly, MoS2 at noncytotoxic doses notably increased the bioaccumulation of Sb(III, V) in algae, causing aggravated oxidative damage, photosynthetic inhibition, and structural alterations. Metabolomics indicated that oxidative stress and membrane permeabilization were primarily associated with down-regulated amino acids involved in glutathione biosynthesis and unsaturated fatty acids. MoS2 co-exposure remarkably decreased the levels of thiol antidotes (glutathione and phytochelatins) and aggravated the inhibition on energy metabolism and ATP synthesis, compromising the Sb(III, V) detoxification and efflux. Additionally, extracellular P was captured by the nanosheets, also contributing to the uptake of Sb(V). Our findings emphasized the nonignorability of TMDs even at environmental levels in affecting the ecological hazard of metalloids, providing insight into comprehensive safety assessment of TMDs.

Hydrothermal co-liquefaction of microalgae, sugarcane bagasse, brewer's spent grain, and sludge from a paper recycling mill: Modeling and evaluation of biocrude and biochar yield.

Biomass can be used as an energy source to thermochemical conversion processes to biocrude production. However, the supply and dependence on only one biomass for biocrude production can be an obstacle due to its seasonality, availability, and logistics costs. In this way, biomass waste and agroindustrial residues can be mixture and used as feedstock to the hydrothermal co-liquefaction (co-HTL) process as an alternative to obtaining biocrude. In this sense, the present paper analyzed the biocrude yield influence of the co-HTL from a quaternary unprecedented blend of different biomasses, such as sugarcane bagasse, brewer's spent grain (BSG), sludge from a paper recycling mill (PRM), and microalgae (Chlorella vulgaris). In this way, a simplex lattice design was employed and co-HTL experiments were carried out in a 2000 mL high-pressure stirred autoclave reactor under 275 °C for 60 min, considering 15% of feedstock/water ratio. Significant effects in each feedstock and their blends were analyzed aiming to increase biocrude and biochar yield. It was found that the addition of microalgae is only significant when considered more than 50% into the blend with BSG and PRM sludge to increase biocrude yield.

The fate of antibiotic resistance genes in wastewater containing microalgae treated by chlorination, ultra-violet, and Fenton reaction.

Antibiotic resistance genes (ARGs) and bacteria (ARBs) in the effluent of wastewater treatment plants (WWTPs) are of utmost importance for the dissemination of ARGs in natural aquatic environments. Therefore, there is an urgent need for effective technologies to eliminate WWTP ARGs/ARBs and mitigate the associated risks posed by the discharged ARG in aquatic environments. To test the effective technology for eliminating ARGs/ARBs, we compared the removal of ARGs and ARBs by three different tertiary treatments, namely ultra-violet (UV) disinfection, chlorination disinfection, and Fenton oxidation. Then, the treated wastewater was co-cultured with Chlorella vulgaris (representative of aquatic biota) to investigate the fate of discharged ARGs into the aquatic environment. The results demonstrated that chlorination (at a chlorine concentration of 15 mg/L) and Fenton (at pH 2.73, with 0.005 mol/L Fe2+ and 0.0025 mol/L H2O2) treatment showed higher efficacy in ARG removal (1.8 - 4.17 logs) than UV treatment (15 min) (1.29 - 3.87 logs). Moreover, chlorine at 15 mg/L and Fenton treatment effectively suppressed ARB regeneration while UV treatment for 15 min could not. Regardless of treatments tested in this study, the input of treated wastewater to the Chlorella system increased the number of ARGs and mobile genetic elements (MGEs), indicating the potential risk of ARG dissemination associated with WWTP discharge. Among the wastewater-Chlorella co-culture systems, chlorination resulted in less of an increase in the number of ARGs and MGEs compared to Fenton and UV treatment. When comparing the wastewater systems to the co-culture systems, it was observed that Chlorella vulgaris reduced the number of ARGs and MGEs in chlorination and UV-treated wastewater; however, Chlorella vulgaris promoted ARG survival in Fenton-treated water, suggesting that aquatic microalgae might act as a barrier to ARG dissemination. Overall, chlorination treatment not only effectively removes ARGs and inhibits ARB regeneration but also shows a lower risk of ARG dissemination. Therefore, chlorination is recommended for practical application in controlling the spread of discharged ARGs from WWTP effluent in natural aquatic environments.

Nanoplastics increase algal absorption and toxicity of Cd through alterations in cell wall structure and composition.

Nanoplastics (NPs) may act as carriers of heavy metals and cause complex toxicity to aquatic organisms, while the exact role of NPs in the joint toxicity remains unclear. Here, we investigated the joint toxicity of polystyrene NPs (PS-NPs) and Cd to freshwater algae (Chlorella vulgaris). It was found that PS-NPs (1 mg L-1) could hardly enter algal cells and slightly inhibit algal growth (p < 0.01). The effect of PS-NPs as carriers on the joint toxicity of PS-NPs and heavy metals could be neglected because of the limited adsorption of Cd by PS-NPs, while the PS-NPs altered the cell wall structure and composition, which resulted in the increased algal absorption and toxicity of Cd. Compared to the low dose Cd (0.4 mg L-1) treatment alone, the extracellular and intracellular Cd contents in the cotreatment were significantly increased by 27.3 % and 18.0 %, respectively, due to the increased contents of cell wall polysaccharides (pectin and hemicellulose in particular) by the PS-NPs. Furthermore, after the high dose Cd (2 mg L-1) exposure, the inhibited polysaccharide biosynthesis and the loosen cell wall structure weakened the tolerance of cell wall to abiotic stress, facilitating the entry of PS-NPs into the algal cells and inducing the higher toxicity. These results elucidate the mechanism by which NPs enhance heavy metal toxicity to algae, providing a novel insight into environmental risks of NPs.

Innovative vs classical methods for drying heterotrophic Chlorella vulgaris: Impact on protein quality and sensory properties.

Drying is a necessary step in the microalgae production chain to reduce microbial load and oxidative degradation of the end product. Depending on the differences in applied temperature and treatment time, the process of drying can have a substantial impact on protein quality and aroma, important characteristics determining the incorporation potential in food products. In this study, we compared the drying of heterotrophic Chorella vulgaris with both innovative (agitated thin film drying (ATFD), pulse combustion drying (PCD) and solar drying (SolD)) and commonly used drying techniques (spray drying (SprD) and freeze drying (FD)). To evaluate the impact on protein quality, we evaluated techno-functional properties, in vitro digestibility (INFOGEST) as well as protein denaturation using differential scanning calorimetry (DSC). A sensory analysis was performed by a trained expert panel, combined with headspace solid-phase microextraction (HS-SPME) - gas chromatography-mass spectrometry (GC-MS) to determine volatile organic compounds (VOCs). ATFD was found to increase techno-functional properties such as gelling, water holding and solubility as well as in vitro protein digestibility. These observations could be related to induced cell disruption and protein denaturation by ATFD. Sensory analysis indicated an increased earthy off-flavor after ATFD. Interestingly, the high-temperature PCD led to an increase in cacao odor while low-temperature FD resulted in lower flavor, odors and VOCs. These results demonstrate that protein quality and sensorial properties of C. vulgaris can be steered through the type of drying, which could help in the selection of application-specific drying methods. Overall, this work could promote the incorporation of microalgal single cell proteins in different innovative food products.

Pulsed electric field treatment for preservation of Chlorella suspensions and retention of gelling capacity.

Pulsed electric field (PEF) processing has emerged as an alternative to thermal pasteurization for the shelf-life extension of heat-sensitive liquids at industrial scale. It offers the advantage of minimal alteration in physicochemical characteristics and functional properties. In this study, a pilot-scale continuous PEF processing (Toutlet < 55 °C) was applied to microalgae Chlorella vulgaris (Cv) suspensions (pH = 6.5), which was proposed as a functional ingredient for plant-based foods. Cv suspensions were inoculated with three distinct food spoilage microorganisms (Pseudomonas guariconensis, Enterobacter soli and Lactococcus lactis), isolated from the Cv biomass. PEF treatments were applied with varying electric field strength Eel of 16 to 28 kV/cm, pulse repetition rate f of 100 to 140 Hz, with a pulse width τ of 20 µs and an inlet product temperature Tin of 30 °C. The aim was to evaluate the PEF-induced microbial reduction and monitor the microbial outgrowth during a 10-day cold storage period (10 °C). Maximum inactivation of 4.1, 3.7 and 3.6 logs was achieved (28 kV/cm and 120 Hz) for the investigated isolates, respectively. Under these conditions, the critical electric field strengths Ecrit, above which inactivation was observed, ranged from 22.6 to 24.6 kV/cm. Moreover, repeated PEF treatment resulted in similar inactivation efficiency, indicating its potential to enhance shelf-life further.

Enhancing microalgae biomass production: Exploring improved scraping frequency in a hybrid cultivation system.

Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m-2 d-1). The species' behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and ∼100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production.

Taguchi approach for assessing supercritical CO2 (sCO2) fluid extraction of polyhydroxyalkanoate (PHA) from Chlorella Vulgaris sp. microalgae.

This research explicitly investigates the utilization of Chlorella Vulgaris sp. microalgae as a renewable source for lipid production, focusing on its application in bioplastic manufacturing. This study employed the supercritical fluid extraction technique employing supercritical CO2 (sCO2) as a green technology to selectively extract and produce PHA's precursor utilizing CO2 solvent as a cleaner solvent compared to conventional extraction method. The study assessed the effects of three extraction parameters, namely temperature (40-60 °C), pressure (15-35 MPa), and solvent flow rate (4-8 ml/min). The pressure, flowrate, and temperature were found to be the most significant parameters affecting the sCO2 extraction. Through Taguchi optimization, the optimal parameters were determined as 60 °C, 35 MPa, and 4 ml/min with the highest lipid yield of 46.74 wt%; above-average findings were reported. Furthermore, the pretreatment process involved significant effects such as crumpled and exhaustive structure, facilitating the efficient extraction of total lipids from the microalgae matrix. This study investigated the microstructure of microalgae biomatrix before and after extraction using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Fourier-transform infrared spectroscopy (FTIR) was utilized to assess the potential of the extracted material as a precursor for biodegradable plastic production, with a focus on reduced heavy metal content through inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The lipid extracted from Chlorella Vulgaris sp. microalgae was analysed using gas chromatography-mass spectrometry (GC-MS), identifying key constituents, including oleic acid (C18H34O2), n-Hexadecanoic acid (C16H32O2), and octadecanoic acid (C18H36O2), essential for polyhydroxyalkanoate (PHA) formation.

Chlorella alleviates the intestinal damage of tilapia caused by microplastics.

Polyethylene microplastics (MPs) of the different sizes may result in different response in fish. Studies showed microorganisms adhered to the surface of MPs have toxicological effect. Juveniles tilapia (Oreochromis niloticus, n = 600, 26.5 ± 0.6 g) were dispersed into six groups: the control group (A), 75 nm MP exposed group (B), 7.5 µm group (C) and 750 (D) µm group, 75 nm + 7.5 µm+750 µm group (E) and 75 nm + Chlorella vulgaris group (F), and exposed for 10 and 14 days. The intestinal histopathological change, enzymic activities, and the integrated "omics" workflows containing transcriptomics, proteomics, microbiota and metabolomes, have been performed in tilapia. Results showed that MPs were distributed on the surface of goblet cells, Chlorella group had severe villi fusion without something like intestinal damage, as in other MPs groups. The intestinal Total Cholesterol (TC, together with group E) and Tumor Necrosis Factor α (TNFα, except for group B) contents in group F were significantly increased, cytochrome p450 1a1 (EROD, group B and E) significantly increased, adenosine triphosphate (ATP), lipoprotein lipase (LPL) and caspase 3 (except group B) also significantly increased at 14 d. At 14 days, group E saw considerably higher regulation of the actin cytoskeleton, focal adhesion, insulin signaling pathway, and AGE-RAGE signaling pathway in diabetes complications. Whereas, chlorella enhanced the focal adhesion, cytokine-cytokine receptor interaction, and MAPK signaling pathways. PPAR signaling pathway has been extremely significantly enriched via the proteomics method. Candidatus latescibacteria, C. uhrbacteria, C. abyssubacteria, C. cryosericota significantly decreased caused by MPs of different particle sizes. Carboxylic acids and derivatives, indoles and derivatives, organooxygen compounds, fatty acyls and organooxygen compounds significantly increased with long-term duration, especially PPAR signaling pathway. MPs had a size-dependent long-term effect on histopathological change, gene and protein expression, and gut microbial metabolites, while chlorella alleviates the intestinal histopathological damage via the integrated "omics" workflows.

Microalgal-bacterial immobilized co-culture as living biofilters for nutrient recovery from synthetic wastewater and their potential as biofertilizers.

This study investigates nutrient recovery from synthetic municipal wastewater using co-immobilized cultures of Chlorella vulgaris TISTR 8580 (CV) and plant growth-promoting bacteria, Bacillus subtilis TISTR 1415 (BS) as living biofilters for a subsequent biofertilizer activity. The optimal condition for nutrient recovery was at the 1:1 ratio of CV/BS using mixed guar gum/carrageenan (GG/CG) binders. After 7-day wastewater treatment, the living biofilters removed 86.7 ± 0.5% of ammonium and 99.3 ± 0.3% of phosphates and were tested subsequently as biofertilizers for 20 days to grow selected plants. The highest optimal biomass and chlorophyll a content was 2 ± 0.3 g (CV/BS 3:1) and 12.4 ± 0.7 µg/g (CV/BS 1:1) from cucumber respectively, however, the close-to-neutral pH (8.0 ± 0.3) was observed from sunflower using CV/BS 1:1 living biofilters. Conclusively, the designed living biofilters exhibit the potential to recover nutrients from wastewater and be used as biofertilizers for circular agriculture.

Understanding microplastic aging driven by photosensitization of algal extracellular polymeric substances.

The aging of microplastics (MPs) is extremely influenced by photochemically-produced reactive intermediates (PPRIs), which are mediated by natural photosensitive substances. Algal extracellular polymeric substances (EPS) can produce PPRIs when exposed to sunlight. Nonetheless, the specific role of EPS in the aging process of MPs remains unclear. This work systematically explored the aging process of polystyrene (PS) MPs in the EPS secreted by Chlorella vulgaris under simulated sunlight irradiation. The results revealed that the existence of EPS accelerated the degradation of PS MPs into particles with sizes less than 1 µm, while also facilitating the formation of hydroxy groups on the surface. The release rate of dissolved organic matter (DOM) from PS MPs was elevated from 0.120 mg·L-1·day-1 to 0.577 mg·L-1·day-1. The primary factor contributing to the elevated levels of DOM was humic acid-like compounds generated through the breakdown of PS. EPS accelerated the aging process of PS MPs by primarily mediating the formation of triplet excited states (3EPS*), singlet oxygen (1O2), and superoxide radicals (O2∙-), resulting in indirect degradation. 3EPS* was found to have the most substantial impact. This study makes a significant contribution to advance understanding of the environmental fate of MPs in aquatic environments impacted by algal blooms.

Development of a new sterilization method for microalgae media using calcium hypochlorite as the sterilant.

Calcium hypochlorite (Ca(ClO)2), which can be stably stored in powder form for a long period, is widely used as a disinfectant in various fields. A new sterilization process was developed in the present study, where a microalgal medium was sterilized using 0.02% Ca(ClO)2, followed by complete neutralization of the Ca(ClO)2 within 8 h through catalytic reaction of an MnCl2-Na2EDTA complex and a synergistic effect of glucose. When comparing the growth of Chlorella vulgaris in the autoclaved medium, a 2.65 times greater maximum cell growth was observed in cells grown in the medium prepared by treatment of Ca(ClO)2. This result indicates that denaturation of the medium by heat can hinder the growth of some microorganisms. In the case of cultivation of Euglena gracilis, successful culture growth was achieved without growth inhibition or contamination on a medium prepared in the same manner.

Acrylamide exposure induces growth retardation, neurotoxicity, stress, and immune/antioxidant disruption in Nile tilapia (Oreochromis niloticus): The alleviative effects of Chlorella vulgaris diets.

This study looked at the toxic impacts of water-born acrylamide (ACR) on Nile tilapia (Oreochromis niloticus) in terms of behaviors, growth, immune/antioxidant parameters and their regulating genes, biochemical indices, tissue architecture, and resistance to Aeromonas hydrophila. As well as the probable ameliorative effect of Chlorella vulgaris (CV) microalgae as a feed additive against ACR exposure was studied. The 96-h lethal concentration 50 of ACR was investigated and found to be 34.67 mg/L for O. niloticus. For the chronic exposure study, a total of 180 healthy O. niloticus (24.33 ± 0.03 g) were allocated into four groups in tri-replicates (15 fish/replicate), C (control) and ACR groups were fed a basal diet and exposed to 0 and 1/10 of 96-h LC50 of ACR (3.46 mg/L), respectively. ACR+ CV5 and ACR+ CV10 groups were fed basal diets with 5 % and 10 % CV supplements, respectively and exposed to 1/10 of 96-h LC50 of ACR for 60 days. After the exposure trial (60 days) the experimental groups were challenged with A. hydrophila. The findings demonstrated that ACR exposure induced growth retardation (P˂0.01) (lower final body weight, body weight gain, specific growth rate, feed intake, protein efficiency ratio, final body length, and condition factor as well as higher feed conversion ratio). A substantial decrease in the immune/antioxidant parameters (P˂0.05) (lysozyme, serum bactericidal activity %, superoxide dismutase, and reduced glutathione) and neurotransmitter (acetylcholine esterase) (P˂0.01) was noticed with ACR exposure. A substantial increase (P˂0.01) in the serum levels of hepato-renal indicators, lipid peroxidation biomarker, and cortisol was noticed as a result of ACR exposure. ACR exposure resulted in up-regulation (P˂0.05) of the pro-inflammatory cytokines and down-regulation (P˂0.05) of the antioxidant-related gene expression. Furthermore, the hepatic, renal, brain, and splenic tissues were badly affected by ACR exposure. ACR-exposed fish were more sensitive to A. hydrophila infection and recorded the lowest survival rate (P˂0.01). Feeding the ACR-exposed fish with CV diets significantly improved the growth and immune/antioxidant status, as well as modulating the hepatorenal functions, stress, and neurotransmitter level compared to the exposed-non fed fish. In addition, modulation of the pro-inflammatory and antioxidant-related gene expression was noticed by CV supplementation. Dietary CV improved the tissue architecture and increased the resistance to A. hydrophila challenge in the ACR-exposed fish. Noteworthy, the inclusion of 10 % CV produced better results than 5 %. Overall, CV diets could be added as a feed supplement in the O. niloticus diet to boost the fish's health, productivity, and resistance to A. hydrophila challenge during ACR exposure.

New insights into Chlorella vulgaris applications.

Environmental pollution is a big challenge that has been faced by humans in contemporary life. In this context, fossil fuel, cement production, and plastic waste pose a direct threat to the environment and biodiversity. One of the prominent solutions is the use of renewable sources, and different organisms to valorize wastes into green energy and bioplastics such as polylactic acid. Chlorella vulgaris, a microalgae, is a promising candidate to resolve these issues due to its ease of cultivation, fast growth, carbon dioxide uptake, and oxygen production during its growth on wastewater along with biofuels, and other productions. Thus, in this article, we focused on the potential of Chlorella vulgaris to be used in wastewater treatment, biohydrogen, biocement, biopolymer, food additives, and preservation, biodiesel which is seen to be the most promising for industrial scale, and related biorefineries with the most recent applications with a brief review of Chlorella and polylactic acid market size to realize the technical/nontechnical reasons behind the cost and obstacles that hinder the industrial production for the mentioned applications. We believe that our findings are important for those who are interested in scientific/financial research about microalgae.

Bioadsorption, bioaccumulation and biodegradation of antibiotics by algae and their association with algal physiological state and antibiotic physicochemical properties.

Bioadsorption, bioaccumulation and biodegradation processes in algae, play an important role in the biomagnification of antibiotics, or other organic pollutants, in aquatic food chains. In this study, the bioadsorption, bioaccumulation and biodegradation of norfloxacin [NFX], sulfamethazine [SMZ] and roxithromycin [RTM]) is investigated using a series of culture experiments. Chlorella vulgaris was exposed to these antibiotics with incubation periods of 24, 72, 120 and 168 h. Results show the bioadsorption concentration of antibiotics in extracellular matter increases with increasing alkaline phosphatase activity (AKP/ALP). The bioaccumulation concentrations of NFX, SMZ and RTM within cells significantly increase after early exposure, and subsequently decrease. There is a significant positive antibiotics correlation to superoxide dismutase (SOD), the photosynthetic electron transport rate (ETR) and maximum fluorescence after dark adaptation (Fv/Fm), while showing a negative correlation to malondialdehyde (MDA). The biodegradation percentages (Pb) of NFX, SMZ and RTM range from 39.3 - 97.2, 41.3 - 90.5, and 9.3 - 99.9, respectively, and significantly increase with increasing Fv/Fm, density and chlorophyll-a. The accumulation of antibiotics in extracellular and intracellular substances of C. vulgaris is affected by antibiotic biodegradation processes associated with cell physiological state. The results succinctly explain relationships between algal growth during antibiotics exposure and the bioadsorption and bioaccumulation of these antibiotics in cell walls and cell matter. The findings draw an insightful understanding of the accumulation of antibiotics in algae and provide a scientific basis for the better utilization of algae treatment technology in antibiotic contaminated wastewaters. Under low dose exposures, the biomagnification of antibiotics in algae is affected by bioadsorption, bioaccumulation and biodegradation.