Extraction and characterization of microalgae-derived phenolics for pharmaceutical applications: A systematic review

Effects of Chlorella sp. and Schizochytrium sp. extracts on growth indices, body composition, and gene expression profiles in rainbow trout (Oncorhynchus mykiss)

This study assessed the impact of dietary Chlorella sp. and Schizochytrium sp. extracts on growth performance, feed utilization, body composition, and gene expression related to growth, digestion, antioxidant defense, and immune response in rainbow trout (Oncorhynchus mykiss). A total of 180 fish (average weight 8.92 ± 0.04 g) were randomly distributed into 12 fiberglass tanks (400 L, 15 fish per tank, three replicates per treatment). Fish were divided into four dietary groups for 60 days: 0 % (Control), 0.5 % Chlorella sp. extract (CH), 0.5 % Schizochytrium sp. extract (SC), and a combined 0.25 % Chlorella sp. and 0.25 % Schizochytrium sp. (CH + SC). At trial end, fish in the CH + SC group had a final weight (FW) of 27.06 ± 0.28 g, significantly higher than other groups (P < 0.05), with improved growth parameters (P < 0.05). While body composition showed no differences in moisture, lipid, or ash content, crude protein was significantly higher in CH + SC (P < 0.05). Gene expression analysis showed upregulation of the growth hormone GH-I gene in the CH + SC group (P < 0.05). Genes related to digestive enzymes (trypsin, lipase, amylase) were also upregulated in all microalgae groups, with the highest levels in CH + SC (P < 0.05). Additionally, antioxidant genes (SOD, CAT, GPx) and immune-related genes (LYZII, TNF-α, IL-1β) showed elevated expression in CH + SC (P < 0.05). This study demonstrated that a diet containing Chlorella sp. and Schizochytrium sp. extracts supports growth, enhances nutrient utilization, and upregulates genes related to antioxidant and immune function in rainbow trout. Further research is recommended to assess functional immune responses and enzyme activities to confirm these physiological effects.

Mitigation of Salt Stress in Lactuca sativa L. var. Gentile Rossa Using Microalgae as Priming Agents

Using renewable biomass in agriculture, particularly microalgae as a biostimulant, offers economic and environmental sustainability benefits by reducing costs, improving nutrient cycling, and enhancing water use efficiency. Microalgae contain bioactive compounds that boost crop tolerance to environmental stresses, including salinity. Saline soils, characterized by elevated sodium chloride (NaCl) levels, negatively impact many crops, resulting in low productivity and high remediation costs. Therefore, this study evaluates the biostimulant properties of a microalgae-based commercial preparation (MR) on lettuce (Lactuca sativa L.) plants grown hydroponically and exposed to saline stress. The extract was chemically characterized through elemental analysis, lipid composition (gas chromatography with flame ionization detector-GC-FID), the determination of functional groups (Fourier Transformed Infrared-FT-IR), structure (1H,13C Nuclear Magnetic Resonance-NMR), with their hormone-like activity also assessed. Lettuce plants were treated with or without the microalgae blend, in combination with 0, 50 mM, or 100 mM NaCl. The contents of nutrients, soluble proteins, chlorophylls, and phenols, as well as the lipid peroxidation, antioxidants and root traits of lettuce plants, were estimated. The microalgae applied to salt-stressed plants resulted in a significant increase in biomass, protein, and chlorophyll contents. Additionally, significant effects on the secondary metabolism and mitigation of salinity stress were observed in terms of increased phenol content and the activity of antioxidant enzymes, as well as decreased lipid peroxidation. The potassium (K+) content was increased significantly in plants treated with 100 mM NaCl after addition of microalgae, while the content of sodium (Na+) was concurrently reduced. In conclusion, our results demonstrate that using microalgae can be a potent approach for improving the cultivation of Lactuca sativa L. under saline stress conditions.

Algae Incorporation and Nutritional Improvement: The Case of a Whole-Wheat Pasta

Algae contain high-quality proteins, dietary fiber, minerals, and phenolic compounds, making them promising alternative ingredients. Since pasta is consumed worldwide, it can be an effective vehicle for incorporating algae. This study compares the nutritional and antioxidant composition of whole-wheat pasta without and with enrichment of an algae mixture (containing Himanthalia elongata and Spirulina) and ascertains the influence of the cooking procedure on their features. Spirulina and H. elongata were also analyzed in parallel for comparison purposes. Macronutrients, chlorides and salt, total and free amino acid profiles, and antioxidant properties (total phenolic content and ferric reducing antioxidant power) were analyzed using AOAC, Mohr's, high performance liquid chromatography with fluorescence detection, and spectrophotometric methods, respectively. The results show a significant increase in fat (70.4%), protein (29.7%), ash (26.5%), and total amino acid (except for serine, tryptophan, isoleucine, and threonine) contents in the raw algae-enriched pasta. The antioxidant activity was also higher (4.15 versus 3.68 g ferrous sulfate eq./g dw, respectively). After cooking, protein, dietary fiber, total amino acids (except threonine) and antioxidant activity were stable in the algae-enriched pasta. Thus, algae can be an excellent ingredient for food applications with health benefits.

Rapid Screening of Microalgae as Potential Sources of Natural Antioxidants

In order to rapidly screen microalgae species as feedstocks for antioxidants, extracts were obtained from 16 microalgae strains (under 11 genera, 7 classes) using two methods: a one-step extraction with ethanol/water and a three-step fractionating procedure using hexane, ethylacetate, and water successively. Measuring the total phenol content (TPC), total carotenoid content (TCC), and antioxidant activity of the extracts, indicating TPC and TCC, played an important role in determining the antioxidant activity of the microalgae. A weighted scoring system was used to evaluate the antioxidant activity, and the scores of microalgal samples from two extraction methods were calculated using the same system. Among the investigated microalgae, Euglena gracilis SCSIO-46781 had the highest antioxidant score, contributing to high TPC and TCC, followed by Arthrospira platensis SCSIO-44012, Nannochloropsis sp. SCSIO-45224, Phaeodactylum tricornutum SCSIO-45120, and Nannochloropsis sp. SCSIO-45006, respectively. Additionally, the above-mentioned five strains are currently being applied in commercial production, indicating this system could be effective not only for screening microalgal antioxidants, but also for screening microalgal species/strains with strong adaptation to environmental stress, which is a critical trait for their commercial cultivation.

Biological and metabolic effects of the association between the microalga Galdieria sulphuraria and the fungus Penicillium citrinum

Contamination of microalgae cultures can reduce their productivity and affect the quality of biomass and valuable bioproducts. In this article, after having isolated and identified for the first time the filamentous fungus Penicillium citrinum from heterotrophic cultures of the red polyextremophilic microalga Galdieria sulphuraria, we investigated the biological and metabolic significance of this alga-fungus association. In the same medium, both organisms grow better in each other's presence than separately. Both cell density and cell size of G. sulphuraria increase in co-cultures compared to pure alga cultures. In co-cultures, despite very severe growth conditions, the load of P. citrinum increases compared to pure fungus cultures. Optical microscope images have shown physical contact between cells of P. citrinum hyphae and G. sulphuraria which, however, retain their morphology and cell wall intact. GC-MS-based metabolomics analysis of metabolites excreted in the culture medium shows that pure cultures of the fungus and alga and co-cultures of alga plus fungus can be easily differentiated based on their metabolic products. Indeed, a richer assortment of extracellular metabolites (comprising both products of primary and secondary metabolism) is a distinct feature of co-cultures compared to both pure alga and pure fungus cultures.

Bioaccessibility and bioactivities of phenolic compounds from microalgae during in vitro digestion and colonic fermentation

Microalgae are a developing novel source of carbohydrates, phenolic compounds, carotenoids and proteins. In this study, in vitro digestion and colonic fermentation were conducted to examine the total phenolic content and potential antioxidant activity of four microalgal species (Chlorella sp., Spirulina sp., Dunaliella sp., and Isochrysis sp.). The bioaccessibility of targeted phenolic compounds and the short-chain fatty acid (SCFA) production were also estimated. Particularly, Spirulina sp. exhibited the highest total phenolic content (TPC) and free radical scavenging (2,2'-diphenyl-1-picrylhydrazyl, DPPH) capacity after gastrointestinal digestion of 7.93 mg gallic acid equivalents (GAE) per g and 2.35 mg Trolox equivalents (TE) per g. Meanwhile, it had the highest total flavonoid content (TFC) of 1.07 quercetin equivalents (QE) per g after 8 h of colonic fermentation. Dunaliella sp. and Isochrysis sp. showed comparable ferric reducing antioxidant power (FRAP) of 4.96 and 4.45 mg QE per g after 4 h of faecal reaction, respectively. p-hydroxybenzoic and caffeic acid almost completely decomposed after the intestine and fermented in the colon with the gut microflora. In Dunaliella sp. and Isochrysis sp., these phenolic acids were found in the colonic fermented residual, probably due to the presence of dietary fibre and the interactions with other components. All four species reached the highest values of SCFA production after 16 h, except Spirulina sp., which displayed the most increased total SCFA production after 8 h of fermentation. It is proposed that Spirulina sp. could be more beneficial to gut health.

Sustainable Microalgae and Cyanobacteria Biotechnology

Marine organisms are a valuable source of new compounds, many of which have remarkable biotechnological properties, such as microalgae and cyanobacteria, which have attracted special attention to develop new industrial production routes. These organisms are a source of many biologically active molecules in nature, including antioxidants, immunostimulants, antivirals, antibiotics, hemagglutinates, polyunsaturated fatty acids, peptides, proteins, biofuels, and pigments. The use of several technologies to improve biomass production, in the first step, industrial processes schemes have been addressed with different accomplishments. It is critical to consider all steps involved in producing a bioactive valuable compound, such as species and strain selection, nutrient supply required to support productivity, type of photobioreactor, downstream processes, namely extraction, recovery, and purification. In general, two product production schemes can be mentioned; one for large amounts of product, such as biodiesel or any other biofuel and the biomass for feeding purposes; the other for when the product will be used in the human health domain, such as antivirals, antibiotics, antioxidants, etc. Several applications for microalgae have been documented. In general, the usefulness of an application for each species of microalgae is determined by growth and product production. Furthermore, the use of OMICS technologies enabled the development of a new design for human therapeutic recombinant proteins, including strain selection based on previous proteomic profiles, gene cloning, and the development of expression networks. Microalgal expression systems have an advantage over traditional microbial, plant, and mammalian expression systems for new and sustainable microalga applications, for responsible production and consumption.