no chemicals required
Microalgae can produce various types of lipids: triacylglycerols, phospholipids, glycolipids or phytosterols, which contain fatty acids ranging from C12 to C24, often with mono- and poly-unsaturated fatty acids C16 and C18. The lipid content in microalgae varies from 20% to 50% of dry weight. These lipids can be used for energy storage, as energy substrates, as structural components of the cell membrane and for metabolic processes (signal transduction, transcriptional and translational control, intercellular interactions, secretion and transfer of vesicles) [ 60 ]. The number of lipids and the presence or position of double bonds in the carbon chain may vary depending on the type of microalgae and cultivation conditions. Optimal conditions can facilitate the conversion of fatty acids to glycerol-based membrane lipids, while adverse conditions can increase the synthesis of neutral lipids, such as triacylglycerols. Typically, many microalgae contain polyunsaturated fatty acids (PUFAs) such as arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. The main saturated fatty acid is palmitic [ 5 ]. The importance of lipids derived from algae lies in their commercial value as an alternative source for obtaining functional food products from their PUFAs, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as their precursor α-linolenic acid [ 60 ]. Most microalgae with high omega-3 content are marine species, for example, Schizochytrium sp. and Nannochloropsis sp. However, freshwater species, for example, Desmodesmus sp., have also been investigated as a source of omega-3 long-chain PUFA, EPA and DHA acids [ 61 , 62 ]. It was found that freshwater microalgae species produce biomass with a lower amount of PUFA.
Since the human body is not able to produce some essential fatty acids, they must be obtained from food or using various food additives, often obtained from fish and fish oil. However, due to the increased interest in the modern world for vegetarian and vegan diets, microalgae can become an alternative source of these nutritional supplements. In addition, many types of fatty fish contain traces of heavy metals that can adversely affect health and cause neurotoxic effects. Depending on the cultivation conditions and the composition of the nutrient medium, the profile of fatty acids may vary for the same types of microalgae. For example, Scharff et al. [ 63 ] evaluated the effect of the photoperiod on the biochemical profile of microalgae Chlorella vulgaris and Scendesmus obliquus and found that longer photoperiods (24:0, 22:2, 20:4) can reduce the synthesis of α-linolenic acid and cause the synthesis of linoleic acid, which is more distinctly observed for C. vulgaris than S. obliquus . On the other hand, Chandra et al. [ 64 ] established that the content of both linoleic and α-linolenic acids increases together with an increase in light intensity, which is a continuous lighting condition for an optimal photoperiod. Choi et al. [ 65 ] studied the dependence of biomass productivity and total fatty acid content in microalgae on various lighting conditions (continuous light, light-dark cycle, continuous darkness and continuous darkness with additional flashing light). The analysis found that the use of flashing light significantly increased the growth rate of Chlorella vulgaris and the concentration of fatty acids in the biomass. Carpio et al. [ 66 ] estimated the lipid content and profile in the biomass of the microalgae Chlorella vulgaris Beij at various concentrations of Fe and CO 2 . It was found that the most intensive growth of biomass (460.0 ± 10 mg/L of dry biomass) was observed at a concentration of Fe (4.8 × 10 −5 mol Fe/L) with 2% CO 2 . While the total lipid content (27.0 ± 0.8%) was maximum at a concentration of Fe (2.4 × 10 −5 mol Fe/L) and 2% CO 2 . Thus, we can conclude that the concentration of iron and other elements also affects the total lipid content, which can significantly affect the profile of fatty acids [ 67 ]. Abd El Baky et al. [ 68 ] studied production, lipid accumulation, and the profile of fatty acids in the microalgae Dunaliella salina . By varying the CO 2 aeration from 0.01% to 12.0%, a 20-fold increase in the lipid content in Dunaliella salina was obtained. Ramirez-Lopez et al. [ 69 ] suggested a new culture medium stimulating the growth of biomass and lipid accumulation for the microalga Chlorella vulgaris . In the process of optimizing the component composition of the medium, the contents of sodium nitrate, ammonium bicarbonate, heptahydrate of magnesium sulfate, potassium dihydrogen phosphate, dipotassium phosphate and diammonium phosphate were varied. Using a new culture medium, it was possible to increase biomass productivity by 40% and an 85% lipid concentration. The concentration of some components of the nutrient media was reduced to 50%. Josephine et al. [ 70 ] studied the influence of growth factors and the optimization of the collection time of Chlorella vulgaris to increase lipid production. An exogenous supplement called the chlorella growth factor (CGF) significantly increased biomass and lipid levels, which determined its potential as a biomass growth promoter in large-scale production. It was found that nitrogen starvation favored the synthesis of more unsaturated fatty acids than saturated ones.
Cultivation of Chlorella vulgaris in the presence of sodium selenite and chromium (III) chloride yielded a biologically active lipid complex, including selenium and chromium [ 71 ]. The authors evaluated the effect of the obtained complex on the energy metabolism of rats subjected to experimentally induced diabetes mellitus. It was found that in rats, the selenium-chrome-lipid complex from the Chlorella improved energy metabolism. The authors concluded that this complex in comparison with inorganic forms of chromium and selenium has potential for regulating energy metabolism in people with diabetes. It was found that the energy metabolism of rats increased when using a biologically active lipid isolated from the microalgae biomass.
Anthony et al. [ 72 ] presented a column chromatography technique for sequential isolation of several biologically active substances from the Chlorella vulgaris biomass (a nucleotide-peptide complex enriched with vitamins, minerals and polysaccharides, lipids and carotenoids). The proposed method [ 70 ] allowed to obtain an increased yield of lipids (18%) and lutein (9%) without foreign impurities of chlorophyll. The highest lipid content was noted in microcultures of microalgae Haematococcus pluvialis, Scenedesmus obliquus and Chlorella vulgaris . The amount of lipids in these microalgae cultures is 19.61 ± 0.58%, 17.13 ± 0.51% and 16.24 ± 0.48%, respectively. The fat content in the Neochloris cohaerens cell culture was 6.61 ± 0.19%, which is 1.35 times higher than the lipid content in the dry biomass of Chlamydomonas reinhardtii microalgae (4.90 ± 0.14%), but less than in the microbial cell culture of Botryococcus braunii and Nannochloropsis gaditana (7.23 ± 0.21% and 7.84 ± 0.13%, respectively). Further study of the microbial lipid profile of microorganisms Chlorella vulgaris, Botryococcus braunii, Neochloris cohaerens, Chlamydomonas reinhardtii and Nannochloropsis gaditana was carried out using gas chromatography. A reagent for transesterification of triglycerides of fatty acids was preliminarily prepared. The studied samples of microalgae ( Chlorella vulgaris, Botryococcus braunii, Neochloris cohaerens, Chlamydomonas reinhardtii and Nannochloropsis gaditana ) were characterized by a diverse fatty acid composition ( Table 8 ). It was found that the fatty acid composition of the studied microcultures is represented by high-molecular-weight polyunsaturated fatty acids.
The results of the study of the fatty acid composition of the microalgae lipid fraction (% of total lipids; table built using combined data from previous studies [ 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 ]).
Fatty Acids * | |||||
---|---|---|---|---|---|
C14:0 | 1.15 ± 0.03 | 2.21 ± 0.06 | 0.72 ± 0.01 | – | – |
C14:1 | − | – | – | 2.38 ± 0.07 | 2.39 ± 0.07 |
C15:0 | – | 10.92 ± 0.34 | 0.13 ± 0.01 | 0.79 ± 0,02 | 1.05 ± 0.03 |
C16:0 | 13.65 ± 0.47 | – | 20.48 ± 0.61 | 17.25 ± 0.51 | 16.18 ± 0.48 |
C16:1 | 1.23 ± 0.03 | 5.04 ± 0.15 | 2.79 ± 0.08 | – | 1.71 ± 0.05 |
C16:2 | 1.84 ± 0.05 | 2.76 ± 0.08 | – | 3.13 ± 0.09 | – |
C16:3 | – | 4.93 ± 0.14 | 0.21 ± 0.01 | – | 37.87 ± 1.13 |
C17:0 | 2.19 ± 0.06 | 21.54 ± 0.70 | 0.15 ± 0.01 | 1.64 ± 0.04 | 4.34 ± 0.12 |
C17:1 | – | – | – | 21.28 ± 0.63 | 0.59 ± 0.01 |
C18:0 | 38.51 ± 1.21 | – | 42.97 ± 1.31 | 42.81 ± 1.28 | – |
C18:1 | 16.79 ± 0.55 | 14.68 ± 0.44 | – | – | 22.26 ± 0.66 |
C18:2 | 7.02 ± 0.20 | – | 8.03 ± 0.23 | 6.29 ± 0.21 | 8.27 ± 0.25 |
C18:3 | 1.47 ± 0.04 | 6.42 ± 0.12 | 3.06 ± 0.09 | 1.73 ± 0.04 | 3.78 ± 0.10 |
C20:0 | 1.22 ± 0.03 | 7.18 ± 0.21 | 4.44 ± 0.13 | – | – |
C22:0 | – | 4.29 ± 1.84 | – | – | 0.52 ± 0.01 |
C22:5 | 1.12 ± 0.03 | – | 0.38 ± 0.01 | 1.31 ± 0.03 | 1.49 ± 0.04 |
C22:6 | 7.87 ± 0.23 | 17.51 ± 0.51 | – | – | – |
C24:0 | – | – | 15.19 ± 0.48 | – | 0.56 ± 0.01 |
C24:1 | – | – | 0.23 ± 0.01 | 0.68 ± 0.02 | – |
* C14:0—myristic acid; C14:1—myristooleic acid; C15:0—pentadecanoic acid; C16:0—palmitic acid; C16:1—palmitoleic acid; C16:2—hexadecadienoic acid; C16:3—hexadecatrienic acid; C17:0—heptadecanoic acid; C17:1—cis-10-Heptadecenoic acid; C18:0—stearic acid; C18:1—oleic acid; C18:2—linoleic acid; C18:3—linolenic acid; C20:0—arachinic acid; C22:0—behenic acid; C22:5—docosapentaenoic acid; C22:6—docosahexaenoic acid; C24:0—lignoceric acid; C24:1—nervonic acid.
It has been reported that polysaccharides of the microalgae Chlorella sorokiniana can induce the secretion of interleukin 12 (IL12), which activates natural killer cells (NKs) and leads to the differentiation of T helper cells into Th1 cells. This effect is important in antiviral and antitumor therapies [ 73 ].
Song et al. [ 74 ] selected parameters for the extraction and purification of the polysaccharide from the Arctic strain of Chlorella sp. to evaluate its antioxidant activity. Under optimized conditions, the polysaccharide yield was 9.62 ± 0.11% of dry weight. After its purification, three fractions were obtained: PI, P-II and P-III. The highest antioxidant activity was shown by the P-IIa fraction. Structural analysis showed that P-IIa is a spiran group heteropolysaccharide consisting mainly of rhamnose, arabinose, glucose and galactose.
Liu et al. [ 75 ] presented a method for producing a new type of polysaccharide from the microalga Arthrospira platensis . Microalgae were cultured under conditions of nitrogen deficiency in open industrial reservoirs. The maximum productivity of biomass and polysaccharides was 27.5 g/m 2 ·day and 26.2 g/m 2 ·day, respectively. The polysaccharide was extracted with hot water by homogenization under pressure, and purification was carried out by flocculation.
El-Ahmady El-Naggar et al. [ 76 ] extracted and identified water-soluble polysaccharides from the microalga Chlorella vulgaris in order to use them as plant growth stimulants.
Liu et al. [ 77 ] isolated a water-soluble polysaccharide from Haematococcus pluvialis using a DEAE-52 anion exchange column and Sephacryl S400 chromatography. The resulting polysaccharide showed immunomodulatory activity.
Gaignard et al. [ 78 ] investigated 166 species of marine microalgae and cyanobacteria in order to identify strains producing original exopolysaccharides. Forty-five strains with the desired characteristics were isolated. Eight new genera of microalgae producing exopolysaccharides, including polymers with a very original composition, were discovered.
In the course of the studies, it was found that the microalgae cultures of Botryococcus braunii and Haematococcus pluvialis , in comparison with other microalgae cells, are characterized by a high content of carbohydrates: 27.36 ± 0.76% and 21.95 ± 0.74%, respectively. The mass fraction of carbohydrates in the biomass of microalgae Scenedesmus obliquus reaches a value of 13.69 ± 0.34, and the carbohydrate content in the biomass of microalgae Nannochloropsis gaditana is 15.34 ± 0.51. Microalgae Chlamydomonas reinhardtii, Neochloris cohaerens and Chlorella vulgaris synthesize carbohydrates in the amount of 12.48 ± 0.34%, 12.58 ± 0.34% and 12.23 ± 0.33%, respectively.
Microalgae contain various types of pigments: carotenoids (orange color), xanthophylls (yellowish tint), phycobilins (red or blue color) and chlorophylls (green color). The content of carotenoids and chlorophyll in microalgae is usually higher than in some plants [ 79 ].
Carotenoids can be stored in oil droplets, in the stroma of the chloroplast or the cytosol, depending on the type of microalgae. Carotenoids in microalgae are usually present in low concentrations (0.5% μg −1 dry weight), although in some Chlorophyta they can reach up to 10% μg −1 dry weight when cultivated under adverse conditions, as is the case for Dunaliella salina [ 80 ]. Carotenoids play an important role in oxygen photosynthesis, as a direct quencher of reactive oxygen species, as well as in the thermal dissipation of excess energy in the photosynthetic apparatus. Microalgae carotenoids can also be used as antioxidant molecules that can quench free radicals, thereby protecting cells and tissues from oxidative damage, including preventing oxidative spoilage of food products. The main carotenoids of microalgae are β-carotene, lycopene, astaxanthin, zeaxanthin, violaxanthin and lutein. Among them, β-carotene, lutein and astaxanthin are the most studied [ 81 ].
Phycobilins (phycocyanin and phycoerythrin) are found in the stroma of the chloroplasts Cyanobacteria, Rhodophyta, Glucophyta and some cryptomonads. They are highly soluble in water and are widely used in the food industry as dyes and in molecular biology as fluorescent markers [ 79 ].
Chlorophylls are fat-soluble green pigments that are actively involved in the process of photosynthesis [ 82 ]. The chlorophyll content in microalgae varies from 0.5% to 1.0% of dry weight, mainly chlorophyll a, however, some microalgae, for example, Dinophyta also contain chlorophyll b and c [ 81 ].
Microalgae also represent a valuable source of vitamins: A, B1, B2, B6, B12, C, E, biotin, folic acid, pantothenic acid, etc. For example, Isochrysis galbana is an important source of vitamins A and E, folic acid, nicotinic acid, pantothenic acid, biotin, thiamine, riboflavin, pyridoxine, cobalamin, chlorophyll (a and c), fucoxanthin and diadinoxanthin, while Euglena gracilis antioxidant can produce vitamins such as β-carotene and vitamins C and E [ 80 ].
Vitamin B12 refers to water-soluble vitamins and is synthesized in animal products, but absent in plant ones. Vitamin B12 deficiency is common in people following a vegan or vegetarian diet. Some types of microalgae may contain or synthesize vitamin B12, for example, Chlorella sp. and Pleurochrysis carterae . However, it is not always in bioavailable form and further studies are needed to identify potential sources of vitamin B12 among microalgae [ 83 ].
Vitamin E is synthesized in many microalgae, for example, Dunaliella tertiolecta, Tetraselmis suecica, Nannochloropsis oculata, Chaetoceros calcitrans and Porphyridium cruentum . A number of studies indicate that the content of vitamin E in microalgae can be much higher than in plants. In this regard, microalgae are a valuable source for vitamin E production [ 84 ].
Smerilli et al. [ 85 ] studied the dependence of the vitamin C content in the microalga Skeletonema marinoi on the spectral composition and light intensity. It has been found that with an increase in the intensity of ultraviolet light, the content of vitamin C in microalgae increases.
Papadaki et al. [ 86 ] extracted various biologically active substances from microalgae Haematococcus pluvialis and Phaeodactylum tricornutum using ultrasound (to restore β-carotene, astaxanthin, fucoxanthin, eicosapentaenoic and arachidonic acid from selected microalgae, coconut oil was used as solvent). The yield of the targeted biologically active substances (vitamins E, B, C and pigments) reached about 80%.
Grudzinski et al. [ 87 ] studied the mechanism of the adaptive response of microalgae ( Chlorella protothecoides and Chlorella vulgaris ) to the effect of intense illumination (400 μmol photons m −2 s −1 ). It has been established that the color change of microalgae from green to yellow under the influence of intense illumination is associated with the accumulation of xanthophilic pigments, mainly zeaxanthin. The results obtained indicate that the carotenoids synthesized in response to intense illumination are not energetically associated with chlorophylls and are not photosynthetically active. These pigments can potentially be used as antioxidants, they stabilize the membrane and protect cells from intense light.
Soares et al. [ 88 ] investigated various methods for the extraction of lutein and β-carotene from the microalga Desmodesmus sp. When choosing the best extraction method, various types of solvents were analyzed and also their proportional ratio under ultrasonic extraction conditions, extraction efficiency, the effect of pretreatment on the yield of the target product, the stability of the extracts and the assessment of the qualitative and quantitative profile of pigments.
Pataro et al. [ 89 ] evaluated the effect of pretreatment by pulsed electric fields on the efficiency of the release of carotenes and chlorophyll a from the microalgae Nannochloropsis oceanica using supercritical CO 2 extraction. The joint use of these processes contributed to a significant increase in the yield of the studied pigments.
Singh et al. [ 90 ] studied the effect of stressful conditions on the carotene yield of Dunaliella salina microalgae and evaluated the antioxidant and cytotoxic activity of the obtained carotene-enriched extracts. Stress conditions were created by varying the concentrations of salt, nitrogen and the temperature of cultivation. It was shown that D. salina grown under various stress conditions (varying NaCl concentration and temperature) increases carotene production. An increase in antioxidant and cytotoxic activities is caused by the accumulation of carotenes.
Sathasivam et al. [ 91 ] selected the optimal concentrations of NaCl and KNO 3 to intensify the synthesis of β-carotene in the microalga Dunaliella salina KU11. The highest yields of β-carotene (115.5 ± 0.4 μg/mL) were obtained by creating stress conditions for the concentration of salts with a concentration of 2.5 M NaCl and 0.5 g/L KNO 3 .
The pigment complex of microcultures includes carotenoids and chlorophylls a and b [ 88 ]. Depending on the type of microculture and the composition of the nutrient medium, the quantitative content of the pigment complex may vary. The main part of the pigments of the studied microalgae samples ( Chlorella vulgaris , Chlamydomonas reinhardtii , Botryococcus braunii , Scenedesmus obliquus , Neochloris cohaerens , Haematococcus pluvialis and Nannochloropsis gaditana ) are chlorophylls. Analysis of the data ( Table 9 ) allows conclusion that the content of chlorophyll a is predominant in the pigment complexes of microalgae; however, for the microalga Scenedesmus obliquus , the content of chlorophyll b is 1.85-times higher than that of chlorophyll a.
Chlorophyll a and b content in microalgae (table built using combined data from previous studies [ 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 ]).
Microalgae | Content, % | |
---|---|---|
Chlorophyll a | Chlorophyll b | |
4.18 ± 0.12 | 2.53 ± 0.07 | |
3.48 ± 0.09 | 3.61 ± 0.10 | |
3.72 ± 0.09 | 2.17 ± 0.07 | |
3.56 ± 0.09 | 6.58 ± 0.19 | |
6.13 ± 0.18 | 1.57 ± 0.05 | |
3.84 ± 0.13 | 2.46 ± 0.90 | |
3.71 ± 0.10 | 1.72 ± 0.04 |
It was found [ 79 , 80 , 81 ] that in the microalgae Botryococcus braunii , Neochloris cohaerens , Chlamydomonas reinhardtii , Nannochloropsis gaditana and Chlorella vulgaris , the content of chlorophyll a exceeds the quantitative content of chlorophyll b. Therefore the microalgae Botryococcus braunii contains 6.58 ± 0.19 mg/g and 2.17 ± 0.07 mg/g of chlorophyll a and b, respectively. Microalgae cells of Neochloris cohaerens contain 3.9-times less chlorophyll b (6.13 ± 0.18 mg/g and 1.57 ± 0.05 mg/g). Cultures of the genus Chlamydomonas reinhardtii are characterized by a content of 2.53 ± 0.07 mg/g and 1.72 ± 0.04 mg/g of chlorophyll a and b, respectively. The microculture of Nannochloropsis gaditana is slightly inferior to the microculture of the microalga Chlorella vulgaris in the content of chlorophyll a, but not inferior in the content of chlorophyll b.
This section provides a brief analysis of the works aimed at assessing the biological effects of various substances from microalgae.
Oncological diseases are one of the main causes of death in the modern world [ 92 , 93 ]. In recent years, studies on the search for new substances with antitumor properties have become increasingly relevant. Alginates, fucoidans, zosterol, unique sulfated polysaccharides, enzymes and peptides of microalgae possess antitumor activity [ 94 ].
Lauritano et al. [ 95 ] analyzed the antitumor properties of extracts from 32 species of microalgae against human melanoma cells A2058. Different types of algae were grown under three different cultivation conditions, the studied extracts were tested for possible antioxidant, anti-inflammatory, antitumor, antidiabetic, antibacterial and antibiofilm activities. One clone of the S. marinoi species (FE60) exhibited antitumor activity on human melanoma cells A2058, but only when cultured under nitrogen starvation. Another clone, FE6, was not active against cancer cells. Both clones (FE60 and FE6) exhibited antibacterial properties, inhibiting the survival of S. aureus . However, FE60 had antibacterial properties only when cultured under nitrogen starvation conditions, and FE6 only under phosphate starvation conditions.
Somasekharan et al. [ 96 ] evaluated the antitumor activity of an aqueous extract of microalgae from Canadian waters against various human cancer cell lines, including lung, prostate, stomach, breast, pancreas cancer and osteosarcoma. The authors analyzed the ability of microalgae extract to inhibit the formation of colonies in cancer cells. In vitro microalgae extract showed pronounced anticolony-forming activity.
Chen et al. [ 97 ] extracted sulfated polysaccharides from filamentous microalgae Tribonema sp. and tested their activity on liver cancer cells, HepG2. The MTT test showed that the sulfated polysaccharide from Tribonema sp. possessed antitumor activity, causing induced cell apoptosis.
Samarakoon et al. [ 98 ] studied the antitumor activity of the alcoholic fatty acid ester synthesized by the microalgae Phaeodactylum tricornutum Bohlin. Antitumor activity was evaluated for three different cancer cell lines (human leukemia (HL-60), human lung cancer (A549) and mouse melanoma (B16F10)). The strongest suppression of cancer cell growth was observed in HL-60 (IC 50 = 65.15 μM) compared with other cancer cells in vitro.
Jabeen et al. [ 99 ] estimated the effect of enzymatic treatment on the antitumor activity of microalgae extracts. Before extraction, the microalgae cells were treated with cellulase and lysozyme. The antitumor activity of the extracts was evaluated against four cancer cell lines (A549, MCF-7, MDA MB-435, LNCap).
Recently, more and more research has been aimed at finding alternative antimicrobial agents, in connection with the progressive problem of microbial resistance, arising from the widespread use of antibiotics in the modern world. Microalgae are able to synthesize a number of metabolites with antimicrobial, antiviral and antifungal properties. In addition, some microalgae can grow under quite extreme conditions, which leads to the synthesis of unique substances for adaptation to changing environmental conditions. Thus, the content of biologically active substances directly depends on the environmental conditions of cultivation. It is known that many algae can synthesize a chemical defense system in order to survive in a competitive environment. Lutein and ferulic acid, polyunsaturated fatty and organic acids, active metabolites and other unique biologically active substances isolated from microalgae exhibit antimicrobial activity [ 100 ].
Krishnakumar et al. [ 101 ] estimated the antimicrobial activity of biologically active metabolites produced by the microalgae Dunaliella salina . It was found that the highest antimicrobial activity was shown by biologically active substances extracted with a mixture of chloroform and methanol.
Kilic et al. [ 102 ] studied the influence of environmental components and cultivation conditions on the synthesis of antimicrobial substances by microalgae of the genus Dunaliella . The most productive Dunaliella species ( Dunaliella sp. 1–4) with high biomass yield and the most resistant to various pollutants were selected. It was established that the highest antimicrobial activity was exerted by biologically active substances produced by microalgae Dunaliella sp. 2. The optimal conditions for the cultivation of biomass for the synthesis of biologically active substances with the highest antimicrobial activity (1.0 g/L nitrogen, 20% (weight/volume) NaCl, light intensity 4800 lux, cultivation time 14 days) were selected. Various types of solvents were analyzed (ethanol, methanol, hexane, chloroform, Tris-HCl and water) for the extraction of biologically active substances. The highest antimicrobial activity among the studied solvents was exerted by biologically active substances extracted with chloroform. When analyzing the obtained biologically active substances, it was suggested that lutein and ferulic acid were the main compounds responsible for higher antimicrobial activity under stressful conditions. The authors view Dunaliella sp. 2 as a safe biomaterial and recommend its use in the field of pharmacology in accordance with its biologically active properties.
The antioxidant is a biological molecule that protects the body or vital compounds from oxidative processes under the influence of radicals [ 103 ]. Many natural antioxidants are often included in various cosmetics as an active ingredient and to protect their components from oxidative processes. Antioxidants are also actively used in the production of functional foods [ 104 , 105 ]. Microalgae, as photosynthetic organisms, are often exposed to reactive oxygen species, as a result of which they can accumulate various antioxidant complexes and have developed a mechanism for protecting cells from the action of free radicals. The wide variety of species, the possibility of modulation of growth and simplicity of cultivating microalgae mean they can be considered one of the promising natural resources for the production of antioxidant compounds. Caratinoids, dimethyl sulfoxide, unique phenolic and nitrogen compounds isolated from microalgae possess antioxidant activity of microalgae [ 106 ].
Widowati et al. [ 107 ] investigated the antioxidant activity of methanol extracts from three different microalgae: Dunaliella salina, Tetraselmis chuii and Isochrysis galbana clone Tahiti. All three microalgae showed high antioxidant activity. Dunaliella salina and Tetraselmis chuii showed the best result. The inhibition rate in D. salina was 62.19% at a concentration of 500 ppm, and T. chuii showed the best result (71.36%) at a concentration of 1000 ppm.
Phenolic compounds play an important role in the classification of antioxidants in plants. However, the role of phenolic compounds as antioxidants in microalgae remains unknown. Gürlek et al. evaluated the antioxidant activity of a number of phenolic compounds obtained from Galderia sulphuraria, Neochloris texensis, Stichococcus bacillaris, Ettlia carotinosa, Chlorella minutissima, Schizochytrium limacinum, Crypthecodinium cohnii and Chlorella vulgaris microalgae extracts [ 3 ]. The maximum antioxidant activity and the content of phenolic compounds were detected in the Galderia sulphuraria extract. A high correlation coefficient between antioxidant activity and the content of phenolic compounds was established—in this regard, we can assume that the antioxidant activity of microalgae can be due to the presence of phenolic compounds in their composition.
Blagojevic et al. [ 108 ] studied the effect of nitrogen content on the antioxidant activity and profile of phenolic compounds in ethanol extracts of ten strains of cyanobacteria. As promising producers of antioxidants and phenolic compounds, the authors recommended cyanobacteria: Nostoc, Anabaena and Arthrospira .
Agregán et al. [ 109 ] evaluated the antioxidant potential of extracts obtained using ultrasound from microorganisms Chlorella and Spirulina . It was found that extracts of the studied microalgae as sources of phenolic antioxidants are more suitable for use as a component of human food. The relatively low antioxidant potential (in terms of polyphenols) makes microalgae extracts unsuitable for industrial use, unlike macroalgae.
Dantas et al. [ 110 ] evaluated the antioxidant and antibacterial activity of various extracts from the microalgae Scenedesmus subspicatus . The studied extracts were able to inhibit the growth of Bacillus subtilis . However, only dimethyl sulfoxide (as an extractant) inhibited the growth of Klebsiella pneumoniae and Escherichia coli . Obtaining an aqueous extract (the presence of antioxidant effectiveness has been proven) is an economical method and avoids the use of toxic substances.
Sansone et al. [ 111 ] analyzed the biological activity of the aqueous-alcoholic extract of the microalgae Tetraselmis suecica containing high concentrations of carotenoids. The studied extract had a high antioxidant and reparative activity.
Bioactive peptides obtained after protein hydrolysis can have various beneficial effects. Hu et al. [ 112 ] found that enzymatic hydrolysates of microalgae exhibit antioxidant properties. Chen et al. [ 113 ] evaluated the hepatoprotective effect of the antioxidant peptide obtained by enzymatic hydrolysis from the microalgae Isochrysis Zhanjiangensis on alcohol damage to HepG2 cells.
An inflammatory reaction is a pathological process that occurs in response to damage, irritation or injury. Regardless of what was the first stimulus, the classic inflammatory response includes pain, fever, redness and swelling. Microalgae substances with a unique structure and properties, such as phycocyanin, polysaccharides, monosaccharides, enzymes, polyunsaturated fatty acids, peptides, and polyphenols have anti-inflammatory properties [ 114 ].
Spirulina (Arthrospira platensis) is a highly nutritious blue-green microalgae widely used worldwide as a nutraceutical food supplement. In addition to its nutritional value, it also exhibits therapeutic properties, including anti-inflammatory activity. Spirulina contains a unique component, phycocyanin, which inhibits the formation of pro-inflammatory cytokines such as TNFα, reduces the production of prostaglandin E(2) and inhibits the expression of cyclooxygeanase-2 (COX-2) [ 115 ]. β-carotene, another compound present in Spirulina , the accumulation of which suppresses the transcription of IL-1β, IL-6 and IL-12, inflammatory cytokines, in the macrophage cell line stimulated by lipopolysaccharide or IFNγ [ 116 ].
Spirulina biomass also promotes the growth of probiotic bacteria such as Lactobacillus casei, Streptococcus thermophilus, Bifidobacteria and Lactobacillus acidophilus . Such prebiotic properties of microalgae are caused not only by the presence of polysaccharides in their structure, but also by monosaccharides, enzymes, PUFAs, peptides and polyphenols [ 117 ].
Extracts of Phaeodactylum tricornutum and Chlorella stigmatophora also exhibit anti-inflammatory properties along with some analgesics and antioxidants [ 118 ].
Cardiovascular diseases remain the main global cause of death, which indicates the need to identify all possible factors that reduce primary and secondary risk.
Villar et al. [ 119 ] found that the crude aqueous extract of the microalga Dunaliella tertiolecta has a strong inhibitory effect on human platelet aggregation caused by thrombin, arachidonic acid and ionomycin isolated from microalgae. Extraction of the crude microalgae aqueous extract and subsequent fractionation with solvents with increasing polarity concentrated the activity in more polar fractions.
Ischemic disorders involving platelet aggregation and blood coagulation are the leading cause of disability and death worldwide. Antithrombotic therapy is unsatisfactory and may cause side effects. Thus, there is a need to search for molecules with antithrombotic properties. Marine organisms produce substances with various well-defined environmental functions. In addition, some of these molecules also exhibit pharmacological properties, such as antiviral, anticancer, antiphoid and anticoagulant properties. The study aimed to evaluate, using in vitro tests, the effect of two brown algae extracts and ten marine sponges from Brazil on platelet aggregation and blood coagulation. The results showed that most extracts were able to inhibit platelet aggregation and clotting, as measured by plasma recalcification tests, prothrombin time, activated partial thromboplastin time and fibrinogenolytic activity. On the other hand, five out of ten species of sponges caused platelet aggregation. Marine organisms studied in this paper may have molecules with antithrombotic properties that represent the biotechnological potential for antithrombotic therapy. Further chemical studies should be conducted on active species in order to discover useful molecules for the development of new drugs for the treatment of coagulation disorders [ 120 ].
Microalgae are considered a valuable biological resource, and in recent years they have received great attention. Their economic importance worldwide is associated with a wide range of applications of microalgae, from the food industry to medicine, from immunostimulants to biofuels, from cosmetology to agriculture. They are able to synthesize proteins, polysaccharides, lipids, polyunsaturated fatty acids, vitamins, pigments, enzymes, phycobiliproteins, etc. Biologically active substances from microalgae exhibit antioxidant, antibacterial, antiviral, antitumor, regenerative, antihypertensive, neuroprotective and immunostimulating effects. Microalgae biomass is a promising source of both nutritional and functional additives.
Only a few species of microalgae ( Arthrospira (Spirulina) platensis, Chlorella or Chlorella vulgaris, Dunaliella, Aphanizomenon and Nostoc ) are allowed for human consumption. These microalgae are a promising object for large-scale cultivation due to the high content of biologically active substances and the relatively cheap manufacturing process. Other microalgae species such as Chlamydomonas sp., Chlorococcum sp., Scenedescmus sp., Tetraselmis chuii and Nanochloropsis sp. have established themselves as a source of useful components in aquaculture, feed, fertilizers and cosmetics, but they do not have GRAS (Generally recognized as safe) status yet [ 93 ].
Due to the wide variety of microalgae, high metabolic flexibility and various cultivation conditions, their real potential has not yet been fully evaluated. Researchers working with microalgae are facing the following tasks:
The multifaceted and joint work on these tasks will make it possible to replace the currently unstable production processes with alternative, less destructive ones. Innovative developments for the microalgae production optimization will make their use economically feasible and sought-after in the future.
Conceptualization, V.D. and S.S.; methodology, O.B. and A.P.; formal analysis, N.P. and S.S.; analysis and interpretation of the data, V.D., D.B., D.K. and N.P.; writing—review and editing, O.B., A.P. and S.I.; All authors have read and agreed to the published version of the manuscript.
This research was funded by the Russian Foundation for basic research, grant number 19-316-60001.
The authors declare no conflict of interest.
Authors : Daniel Alexandre Morelli; Pedro Henrique Ribeiro Botene; Gabriella Carlucci Tavares Colombo; Giovana Catussi Paschoalotto; Paulo Sergio de Arruda Ignacio; Anibal Tavares de Azevedo; Antônio Carlos Pacagnella Júnior; Alessandro Lucas da Silva
Addresses : Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil ' Industrial Engineering Research Centre, School of Applied Sciences, University of Campinas-UNICAMP, Limeira SP, Brazil
Abstract : The approach that associates innovative Industry 4.0 technologies with lean production principles is called lean automation (LA). This paper aims to explore LA models, investigating challenges and opportunities to their practical application in micro, small and medium-sized enterprises (MSMEs) in Brazil, contributing to technological development in emerging countries. As such, this article mapped the main combinations of Industry 4.0 and Lean principles, structured a conceptual just-in-time (JIT) delivery model, and characterised the conditions of MSMEs of emerging countries in relation to LA standards. The data collection was generated through a survey, and its analysis was performed using the Promethee-Gaia method. The results allowed us to compare different sectors, revealing their strengths and weaknesses. This study verified that business segments with the worst LA adherences presented low rates in concepts such as: 'planning and scheduling', 'pull-system', 'lot size reductions' and 'cyber security'. We organised a feasible three-steps roadmap for the LA implementation.
Keywords : lean automation; Industry 4.0; I4.0; lean production systems; LPS; just-in-time; JIT; delivery; micro small and medium-sized enterprises; MSMEs; developing countries; survey; Promethee.
DOI : 10.1504/IJSOM.2024.140421
International Journal of Services and Operations Management, 2024 Vol.48 No.4, pp.481 - 510
Received: 21 Jun 2022 Accepted: 24 Jun 2022 Published online: 08 Aug 2024 *
The unsteady flow field in the aerostatic bearing always induces micro-vibrations, which are severely detrimental to the stability and precision of the bearing. Extensive research has been conducted on the mechanism of micro-vibration, but a consensus has not yet been reached. To this end, the large eddy simulation (LES) and proper orthogonal decomposition methods were employed to analyze the flow field of an annular aerostatic bearing in this paper. A mechanism for inducing micro-vibration and the identification of a novel flow behavior were ultimately revealed. First, the accuracy of our LES method has been validated through quantitative comparison with experimental data. Then, the mode decomposition has been conducted to analyze the flow field under various gas supply pressures. The results demonstrate that when the supply pressure P s = 0.4 MPa, the micro-vibration is dominated by a pair of adjacent large-scale vortices with low frequencies in the recess. However, when P s = 0.5 and 0.6 MPa, the convection and shearing processes near the orifice outlet and the rectangular recess inlet become intense, resulting in the displacement of large-scale vortices. Eventually, the small-scale high-frequency pressure fluctuation structures have been also observed, which are closely related to the convection process within recess. With the increase in gas supply pressure, the high-frequency pressure fluctuations at the circular recess outlet gradually diminish, while those at the orifice outlet emerge and gradually enlarge. Meanwhile, the mode dominant frequency is transferred from around 200 kHz to around 1000 kHz. The energy fraction of the high-frequency pressure fluctuations is also greatly increased.
Micro blood analysis technology (μbat): multiplexed analysis of neutrophil phenotype and function from microliter whole blood samples †.
* Corresponding authors
a Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA E-mail: [email protected]
b Morgridge Institute for Research, Madison, WI, USA E-mail: [email protected]
c Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison, Madison, WI, USA
d Department of Pediatrics, School of Medicine and Public Health, University of Wisconsin-Madison, WI, USA
e University of Wisconsin Carbone Cancer Center, University of Wisconsin, Madison, WI, USA
There is an ongoing need to do more with less and provide highly multiplexed analysis from limited sample volumes. Improved “sample sparing” assays would have a broad impact across pediatric and other rare sample type studies in addition to enabling sequential sampling. This capability would advance both clinical and basic research applications. Here we report the micro blood analysis technology (μBAT), a microfluidic platform that supports multiplexed analysis of neutrophils from a single drop of blood. We demonstrate the multiplexed orthogonal capabilities of μBAT including functional assays (phagocytosis, neutrophil extracellular traps, optical metabolic imaging) and molecular assays (gene expression, cytokine secretion). Importantly we validate our microscale platform using a macroscale benchmark assay. μBAT is compatible with lancet puncture or microdraw devices, and its design facilitates rapid operations without the need for specialized equipment. μBAT offers a new method for investigating neutrophil function in populations with restricted sample amounts.
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T. D. Juang, J. Riendeau, P. G. Geiger, R. Datta, M. Lares, R. C. Yada, A. M. Singh, C. M. Seroogy, J. E. Gern, M. C. Skala, D. J. Beebe and S. C. Kerr, Lab Chip , 2024, Advance Article , DOI: 10.1039/D4LC00333K
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