Carotenoids Overproduction in Dunaliella Sp.: Transcriptional Changes and New Insights through Lycopene β Cyclase Regulation

Nitrogen Forms Regulate the Response of Microcystis aeruginosa to Nanoplastics at Environmentally Relevant Nitrogen Concentrations

As essential primary producers, cyanobacteria play a major role in global carbon and nitrogen cycles. Though the influence of nanoplastics on the carbon metabolism of cyanobacteria is well-studied, little is known about how nanoplastics affect their nitrogen metabolism, especially under environmentally relevant nitrogen concentrations. Here, we show that nitrogen forms regulated growth inhibition, nitrogen consumption, and the synthesis and release of microcystin (MC) in Microcystis aeruginosa exposed to 10 μg/mL amino-modified polystyrene nanoplastics (PS-NH2) with a particle size of 50 nm under environmentally relevant nitrogen concentrations of nitrate, ammonium, and urea. We demonstrate that PS-NH2 inhibit M. aeruginosa differently in nitrate, urea, and ammonium, with inhibition rates of 51.87, 39.70, and 36.69%, respectively. It is caused through the differences in impairing cell membrane integrity, disrupting redox homeostasis, and varying nitrogen transport pathways under different nitrogen forms. M. aeruginosa respond to exposure of PS-NH2 by utilizing additional nitrogen to boost the production of amino acids, thereby enhancing the synthesis of MC, extracellular polymeric substances, and membrane phospholipids. Our results found that the threat of nanoplastics on primary producers can be regulated by the nitrogen forms in freshwater ecosystems, contributing to a better understanding of nanoplastic risks under environmentally relevant conditions.

Research Progress in Heterologous Crocin Production

Crocin is one of the most valuable components of the Chinese medicinal plant Crocus sativus and is widely used in the food, cosmetics, and pharmaceutical industries. Traditional planting of C. sativus is unable to fulfill the increasing demand for crocin in the global market, however, such that researchers have turned their attention to the heterologous production of crocin in a variety of hosts. At present, there are reports of successful heterologous production of crocin in Escherichia coli, Saccharomyces cerevisiae, microalgae, and plants that do not naturally produce crocin. Of these, the microalga Dunaliella salina, which produces high levels of β-carotene, the substrate for crocin biosynthesis, is worthy of attention. This article describes the biosynthesis of crocin, compares the features of each heterologous host, and clarifies the requirements for efficient production of crocin in microalgae.

Conception of an environmental friendly O/W cosmetic emulsion from microalgae

The development of eco-friendly cosmetic such as those from microalgae for skin regeneration and collagen synthesis has gained a great interest worldwide. Accordingly, the potential of microalgae biomass as source of anti-aging cosmetic cream with high antioxidant activity has been investigated. Stabilities and sensory characteristics of cosmetic creams supplemented with Spirulina, Tetraselmis sp. and Dunaliella sp. at 0.5, 1.5 and 2.5%, respectively, revealed a conservation of physico-chemical and preliminary stability properties of formulations. To analyze physico-chemical and textural parameters, accelerated stability study was evaluated under two thermal conditions (25 and 40 °C) during 90 days. Results showed that pH values of all formulations were within the limits of normal skin pH range under storage time at 25 and 40 °C. During this period, the colored creams showed a significant changes of a* and b* indices, reflecting the instability of microalgae colors. Microalgae modified the textural characteristics of emulsions. The Tetraselmis sp. containing-cream had the lowest (P < 0.05) values of hardness, springiness, and cohesiveness. The 0.5% Spirulina containing-cream had the best stable consistency and adhesiveness under time and temperature variations. It exhibited the best properties to be used for skin care products. Thanks to their high content in bioactive macromolecules, microalgae considerably improved the antioxidant activity of the new formulated skin creams.

Microalgae as feedstock for bioactive polysaccharides

Due to the increase in industrial demand for new biosourced molecules (notably bioactive exopolysaccharides (EPS)), microalgae are gaining popularity because of their nutraceutical potential and benefits health. Such health effects are delivered by specific secondary metabolites, e.g., pigments, exopolysaccharides, polyunsaturated fatty acids, proteins, and glycolipids. These are suitable for the subsequent uses in cosmetic, nutraceutical, pharmaceutical, biofuels, biological waste treatment, animal feed and food fields. In this regard, a special focus has been given in this review to describe the various methods used for extraction and purification of polysaccharides. The second part of the review provides an up-to-date and comprehensive summary of parameters affecting the microalgae growth and insights to maximize the metabolic output by understanding the intricacies of algal development and polysaccharides production. In the ultimate part, the health and nutraceutical claims associated with marine algal bioactive polysaccharides, explaining their noticeable potential for biotechnological applications, are summarized and comprehensively discussed.

In silico evidence of antiviral activity against SARS-CoV-2 main protease of oligosaccharides from Porphyridium sp

The coronavirus pandemic (COVID-19) has created an urgent need to develop effective strategies for prevention and treatment. In this context, therapies against protease M^pro, a conserved viral target, would be essential to contain the spread of the virus and reduce mortality. Using combined techniques of structure modelling, in silico docking and pharmacokinetics prediction, many compounds from algae were tested for their ability to inhibit the SARS-CoV-2 main protease and compared to the recent recognized drug Paxlovid. The screening of 27 algal molecules including 15 oligosaccharides derived from sulfated and non-sulphated polysaccharides, eight pigments and four poly unsaturated fatty acids showed high affinities to interact with the protein active site. Best candidates showing high docking scores in comparison with the reference molecule were sulfated tri-, tetra- and penta-saccharides from Porphyridium sp. exopolysaccharides (SEP). Structural and energetic analyses over 100 ns MD simulation demonstrated high SEP fragments-M^pro complex stability. Pharmacokinetics predictions revealed the prospects of the identified molecules as potential drug candidates.

Biomolecules from Microalgae and Cyanobacteria: Applications and Market Survey

Nowadays, microalgae and cyanobacteria have become a promising and sustainable source of useful products, thanks to their richness in bioactive metabolites of high value (antibiotics, toxins, pharmaceutically active compounds, plant growth regulators, and others). These photoautotroph microorganisms generate biomass using photosynthesis. This review, which distinguishes microalgae and Cyanobacteria, often called blue-green microalgae, aims to present their classification and taxonomic diversity as the ecological niches occupied by them. In addition, the usages of open ponds and photobioreactors to produce various microalgae and Cyanobacteria strains and the high-value bioactive compounds from these microorganisms are summarized. Finally, the numerous commercial applications of these phytoplanktons in different fields, such as food, dietary supplements, feed, cosmetic, and biofuel applications, are reviewed.

Identification, Characterization, and Expression Analysis of Carotenoid Biosynthesis Genes and Carotenoid Accumulation in Watercress (Nasturtium officinale R. Br.)

Watercress (Nasturtium officinale R. Br.) is an important aquatic herb species belonging to the Brassicaceae family. It has various medicinal properties and has been utilized for the treatment of cancer and other diseases; however, currently available genomic information regarding this species is limited. Here, we performed the first comprehensive analysis of the carotenoid biosynthesis pathway (CBP) genes of N. officinale, which were identified from next-generation sequencing data. We identified and characterized 11 putative carotenoid pathway genes; among these, nine full and two partial open reading frames were determined. These genes were closely related to CBP genes of the other higher plants in the phylogenetic tree. Three-dimensional structure analysis and multiple alignments revealed several distinct conserved motifs, including aspartate or glutamate residues, carotene-binding motifs, and dinucleotide-binding motifs. Quantitative reverse transcription-polymerase chain reaction results showed that the CBP was expressed in a tissue-specific manner: expression levels of NoPSY, NoPDS, NoZDS-p, NoCrtISO, NoLCYE, NoCHXE-p, and NoCCD were highest in the flower, whereas NoLCYB, NoCHXB, NoZEP, and NoNCED were highest in the leaves. Stems, roots, and seeds did not show a significant change in the expression compared to the leaves and flowers. High-performance liquid chromatography analysis of the same organs showed the presence of seven distinct carotenoid compounds. The total carotenoid content was highest in the leaves followed by flowers, seeds, stems, and roots. Among the seven individual carotenoids, the levels of six carotenoids (i.e., 13-Z-β-carotene, 9-Z-β-carotene, E-β-carotene, lutein, violaxanthin, and β-cryptoxanthin) were highest in the leaves. The highest content was observed for lutein, followed by E-β-carotene, and 9-Z-β-carotene; these carotenoids were much higher in the leaves compared to the other organs. The results will be useful references for further molecular genetics and functional studies involving this species and other closely related species.

Potential of three local marine microalgae from Tunisian coasts for cadmium, lead and chromium removals

Metal elements are widely used in various industrial activities and are considered as common water source contaminants. Thus, the development of cost-effective, simple design and efficient processes for trace metal elements removal from contaminated water sources is of great interest. The effects of cadmium, lead and chromium on growth, biomolecules accumulation and metabolic responses of Amphora coffaeiformis, Navicula salinicola and Dunaliella salina isolated from Tunisian coasts were tested. The bioremediation capacities of the three microalgae strains and the mechanisms involved in ions metal removal were also investigated. N. salinicola and D. salina seem to be better tolerating to Cr, while A. coffaeiformis and N. salinicola showed high resistance to Pb. The expression profile analyses by qRT-PCR of the antioxidant defense-related genes revealed that Cd, Pb and Cr treatments induce the up-regulation of catalase and superoxide dismutase coding genes for A. coffaeiformis and D. salina. Regarding N. salinicola, the catalase coding gene seems to be overexpressed after Cd, Pb and Cr exposure while only Cd and Cr induce superoxide dismutase gene overexpression. Moreover, the phytochelatin synthase (a metal chelator synthesis-related gene) was up-regulated in N. salinicola, A. coffaeiformis and D. salina after Cr exposure and also in A. coffaeiformis and D. salina after Cd exposure. While Pb treatments induce overexpression of phytochelatin synthase coding gene only for D. salina. Studied strains showed promising metal removal efficiencies for both Pb and Cr ions metals reached 95% for D. salina. Ion metal removal mechanisms study revealed that intracellular bioaccumulation process is used by D. salina for Cr up-taking. However, both intracellular and extracellular removal mechanisms are involved for Pb and Cr removal using A. coffaeiformis, N. salinicola and for Pb removal using D. salina. FTIR analysis demonstrated that several functional groups as carboxyl, hydroxyl, amino, phosphate and sulfate may participate in the bioadsorption process.

Genome-based identification and comparative analysis of enzymes for carotenoid biosynthesis in microalgae

Microalgae are potential feedstocks for the commercial production of carotenoids, however, the metabolic pathways for carotenoid biosynthesis across algal lineage are largely unexplored. This work is the first to provide a comprehensive survey of genes and enzymes associated with the less studied methylerythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate pathway as well as the carotenoid biosynthetic pathway in microalgae through bioinformatics and comparative genomics approach. Candidate genes/enzymes were subsequently analyzed across 22 microalgae species of lineages Chlorophyta, Rhodophyta, Heterokonta, Haptophyta, Cryptophyta, and known Arabidopsis homologs in order to study the evolutional divergence in terms of sequence-structure properties. A total of 403 enzymes playing a vital role in carotene, lutein, zeaxanthin, violaxanthin, canthaxanthin, and astaxanthin were unraveled. Of these, 85 were hypothetical proteins whose biological roles are not yet experimentally characterized. Putative functions to these hypothetical proteins were successfully assigned through a comprehensive investigation of the protein family, motifs, intrinsic physicochemical features, subcellular localization, pathway analysis, etc. Furthermore, these enzymes were categorized into major classes as per the conserved domain and gene ontology. Functional signature sequences were also identified which were observed conserved across microalgal genomes. Additionally, the structural modeling and active site architecture of three vital enzymes, DXR, PSY, and ZDS catalyzing the vital rate-limiting steps in Dunaliella salina were achieved. The enzymes were confirmed to be stereochemically reliable and stable as revealed during molecular dynamics simulation of 100 ns. The detailed functional information about individual vital enzymes will certainly help to design genetically modified algal strains with enhanced carotenoid contents.

Microalgae Xanthophylls: From Biosynthesis Pathway and Production Techniques to Encapsulation Development

In the last 20 years, xanthophylls from microalgae have gained increased scientific and industrial interests. This review highlights the essential issues that concern this class of high value compounds. Firstly, their chemical diversity as the producer microorganisms was detailed. Then, the use of conventional and innovative extraction techniques was discussed. Upgraded knowledge on the biosynthetic pathway of the main xanthophylls produced by photosynthetic microorganisms was reviewed in depth, providing new insightful ideas, clarifying the function of these active biomolecules. In addition, the recent advances in encapsulation techniques of astaxanthin and fucoxanthin, such as spray and freeze drying, gelation, emulsification and coacervation were updated. Providing information about these topics and their applications and advances could be a help to students and young researchers who are interested in chemical and metabolic engineering, chemistry and natural products communities to approach the complex thematic of xanthophylls.

Production and structure prediction of amylases from Chlorella vulgaris

Amylases are enzymes required for starch degradation and are naturally produced by many microorganisms. These enzymes are used in several fields such as food processing, beverage, and medicine as well as in the formulation of enzymatic detergents proving their significance in modern biotechnology. In this study, a three-stage growth mode was applied to enhance starch production and amylase detection from Chlorella vulgaris. Stress conditions applied in the second stage of cultivation led to an accumulation of proteins (75% DW) and starch (21% DW) and a decrease in biomass. Amylase activities were detected and they showed high production levels especially on day 3 (35 U/ml) and day 5 (22.5 U/ml) of the second and third stages, respectively. The bioinformatic tools used to seek amylase protein sequences from TSA database of C. vulgaris revealed 7 putative genes encoding for 4 α-amylases, 2 β-amylases, and 1 isoamylase. An in silico investigation showed that these proteins are different in their lengths as well as in their cellular localizations and oligomeric states though they share common features like CSRs of GH13 family or active site of GH14 family. In brief, this study allowed for the production and in silico characterization of amylases from C. vulgaris.

Zinc biosorption by Dunaliella sp. AL-1: Mechanism and effects on cell metabolism

Phycoremediation is being considered as an eco-friendly and safe technology for toxics eradication from contaminated aquatic systems. The zinc biosorption capacity of Dunaliella sp. AL-1 was demonstrated. Zinc impacted cell growth and photosynthetic pigments accumulation showing exposure time and concentration-dependent effects. The investigation of the antioxidant protective response to zinc exposition proved a stimulation of guaiacol peroxidase (GPX) activity and an increased rate of total phenolics, flavonoids, condensed tannins and glutathione (GSH). The Box-Behnken design was used to optimize zinc removal conditions by Dunaliella sp. AL-1 strain. The maximum experimental zinc uptake was obtained when zinc concentration, algae dose, initial pH, and contact time were set at 25 mg/L, 0.5 g/L, 7.59 and 13 h 43 min, respectively. Under completely optimized conditions, the fraction of zinc removed intracellularly was much lower than the adsorbed on the cell surface. FTIR analysis Dunaliella sp. AL-1 biomass demonstrated that several functional groups as OH, CH₂, CO, PO, COO and CO may participate in the biosorption process. A comparative proteomic analysis through nano-HPLC coupled to LC-MS/MS, was performed from pre- and post-zinc treatments cells. Among 199 identified proteins, 60 were differentially expressed of which 41 proteins were down-regulated against 19 up-regulated ones. Target proteins have been demonstrated to be implicated in different metabolic processes mainly photosynthesis and antioxidant defenses.

Ecological and Biotechnological Aspects of Pigmented Microbes: A Way Forward in Development of Food and Pharmaceutical Grade Pigments

Microbial pigments play multiple roles in the ecosystem construction, survival, and fitness of all kinds of organisms. Considerably, microbial (bacteria, fungi, yeast, and microalgae) pigments offer a wide array of food, drug, colorants, dyes, and imaging applications. In contrast to the natural pigments from microbes, synthetic colorants are widely used due to high production, high intensity, and low cost. Nevertheless, natural pigments are gaining more demand over synthetic pigments as synthetic pigments have demonstrated side effects on human health. Therefore, research on microbial pigments needs to be extended, explored, and exploited to find potential industrial applications. In this review, the evolutionary aspects, the spatial significance of important pigments, biomedical applications, research gaps, and future perspectives are detailed briefly. The pathogenic nature of some pigmented bacteria is also detailed for awareness and safe handling. In addition, pigments from macro-organisms are also discussed in some sections for comparison with microbes.

Quantitative PCR assay for the simultaneous identification and enumeration of multiple Karenia species

Quantitative PCR (qPCR) is the method of choice for specific detection and quantification of harmful algal bloom (HAB) species. Development of qPCR assay for simultaneous enumeration of species that frequently co-exist in HABs is required. A high sensitivity TaqMan qPCR assay, using probe and primers, located at ITS1-5.8S-ITS2 rDNA region, detecting, specifically, Karenia selliformis, K. bidigitata, and K. mikimotoi, was designed. ITS1-5.8S-ITS2 rDNA region copy numbers per Karenia cell genome were estimated to 217.697 ± 67.904, allowing cell quantification. An application of the designed methodology in field samples has been conducted, and it showed high sensitivity (detection of around 10^-1 cell/100 mg of bivalve mollusk tissue, equivalent to about 20 copies of the target sequence). We suggest that the optimized method could contribute to early detection of three closely related Karenia species in seafood cultivating areas to promote control quality, guarantee a fast and effective intervention, and improve public health prevention.

Deciphering the Biological Activities of Dunaliella sp. Aqueous Extract from Stressed Conditions on Breast Cancer: from in Vitro to in Vivo Investigations

In order to harness local resources to improve well-being and human health, we aim in this study to investigate if the microalgae Dunaliella sp. isolated from the Tunisian coastal zone possesses any anticancer activity. Dunaliella sp. was cultured under normal (DSC) or stressed (DSS) conditions and extracted using different procedures. The biological activity assessment was performed on the Triple Negative Breast Cancer (TNBC) using 4T1 murine cells as a model. Results indicate that: (i) aqueous extract was the most cytotoxic compared to ethanolic and hydroalcoholic extracts; (ii) DSS activity was superior to that of DSC. DSS extracts induced apoptosis rather than necrosis, as evidenced by DNA fragmentation, PARP-1 cleavage and caspase-3 activation. Evaluation in an orthotopic TNBC model validated the anticancer activity in vivo. Intratumoral injection of DSS extract resulted in reduced tumor growth and an enhanced immune system activation. On the transcriptional side, the expression level of the immunosuppressive enzyme Arg-1 was decreased, as well as those of NOS-2 and COX-2 genes. These results suggest a potential anticancer activity of Tunisian Dunaliella sp. deserving further attention.