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A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 31378

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Prof. Dr. Eduardo Jacob-Lopes

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Guest Editor

Food Science and Technology Department, Federal University of Santa Maria, Santa Maria, RS, Brazil
Interests: microalgae biotechnology; bioprocess engineering; sustainable engineering; microalgae-based processes and products
Special Issues, Collections and Topics in MDPI journals

Dr. Leila Queiroz Zepka

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Guest Editor

Food Science and Technology Department, Federal University of Santa Maria, Santa Maria, RS, Brazil
Interests: microalgae biotechnology; microalgae-based products; natural pigments; carotenoids; chlorophylls; bioactive compounds
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microalgae and their extracts represent a vast and unexplored source of compounds with biological activity. These compounds show nutraceutical, antimicrobial, anti-inflammatory, anti-aging, aggregative, vasoconstricting, hypocholesterolemic, antioxidant, immunosuppressive, photoprotective, and neurotransmitting activities. Although hundreds of these metabolites have been identified in cultures of photosynthetic microorganisms, the induction of synthesis is unknown in most cases, the separation and recovery of the compounds need to be optimized and, thus, their inclusion into commercial products awaits further research and development. Chemically, the compounds with biological activity can be grouped into proteins/enzymes, fatty acids, sterols, pigments, vitamins, alkaloids, mycosporine-like amino acids, and other compounds not fitting into these aforementioned categories. This Special Issue is dedicated to all aspects of the production of specialty chemicals from microalgae, covering the selecting of the species, the definition of the culture conditions, isolating and purifying the target molecule, and demonstration of the biological activity through clinical tests.

Dr. Eduardo Jacob-Lopes
Dr. Leila Queiroz Zepka
Guest Editors

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Keywords

biosynthesis
culture conditions
bioactive compounds
biological activity
biorefinery
proteins
peptides
antifreeze proteins
enzymes
carbohydrates
exocellular polysaccharides
carbohydrate-binding proteins
lipids
fatty acids
chlorophylls
carotenoids
phycobiliproteins
vitamins
minerals
trace elements
sterols
secondary metabolites
downstream processing
purification
safety
regulatory issues
clinical tests

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Published Papers (10 papers)

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Research

35 pages, 5285 KiB

Open AccessArticle

Lipidomic Characterization and Antioxidant Activity of Macro- and Microalgae Blend

by Francisca Marques, Diana Lopes, Tiago Conde, Tânia Melo, Joana Silva, Maria Helena Abreu, Pedro Domingues and Maria Rosário Domingues

Life 2023, 13(1), 231; https://doi.org/10.3390/life13010231 - 13 Jan 2023

Cited by 3 | Viewed by 2615

Abstract

Macro- and microalgae are currently recognized sources of lipids with great nutritional quality and attractive bioactivities for human health promotion and disease prevention. Due to the lipidomic diversity observed among algae species, giving rise to different nutritional and functional characteristics, the mixture of macro- and microalgae has the potential to present important synergistic effects resulting from the complementarity among algae. The aim of this work was to characterize for the first time the lipidome of a blend of macro- and microalgae and evaluate the antioxidant capacity of its lipid fraction. Fatty acids were profiled by GC-MS, the polar lipidome was identified by high resolution LC-MS, and ABTS^+• and DPPH^• assays were used to assess the antioxidant potential. The most abundant fatty acids were oleic (18:1 n-9), α-linolenic (18:3 n-3), and linoleic (18:2 n-6) acids. The lipid extract presented a beneficial n-6/n-3 ratio (0.98) and low values of atherogenic (0.41) and thrombogenic indices (0.27). The polar lipidome revealed 462 lipid species distributed by glycolipids, phospholipids, and betaine lipids, including some species bearing PUFA and a few with reported bioactivities. The lipid extract also showed antioxidant activity. Overall, the results are promising for the valorization of this blend for food, nutraceutical, and biotechnological applications. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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19 pages, 2062 KiB

Open AccessArticle

Improvement in the Sequential Extraction of Phycobiliproteins from Arthrospira platensis Using Green Technologies

by Wanida Pan-utai, Siriluck Iamtham, Sumitra Boonbumrung and Juta Mookdasanit

Life 2022, 12(11), 1896; https://doi.org/10.3390/life12111896 - 15 Nov 2022

Cited by 10 | Viewed by 2809

Abstract

Arthrospira platensis (commercially known as Spirulina) is an excellent source of phycobiliproteins, especially C-phycocyanin. Phycobiliproteins are significant bioactive compounds with useful biological applications. The extraction process plays a significant role in downstream microalga production and utilisation. The important pigments found in A. platensis include chlorophyll and carotenoids as nonpolar pigments and phycobiliproteins as polar pigments. Supercritical fluid extraction (SFE) as a green extraction technology for the high-value metabolites of microalgae has potential for trends in food and human health. The nonpolar bioactive compounds, chlorophyll and carotenoids of A. platensis, were primarily separated using supercritical carbon dioxide (SC-CO₂) solvent-free fluid extraction pressure; the temperature and ethanol as cosolvent conditions were compared. The residue from the A. platensis cells was subjected to phycobiliprotein extraction. The phosphate and water extraction of A. platensis SFE residue were compared to evaluate phycobiliprotein extraction. The SFE results exhibited higher pressure (350 bar) and temperature extraction (50 °C) with ethanol-free extraction and increased nonpolar pigment. Phycobiliprotein yield was obtained from A. platensis SFE residue by ethanol-free buffer extraction as a suitable process with antioxidant properties. The C-phycocyanin was isolated and enhanced to 0.7 purity as food grade. This developed method can be used as a guideline and applied as a sustainable process for important pigment extraction from Arthrospira microalgae. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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17 pages, 1466 KiB

Open AccessArticle

Study of the Polysaccharide Production by the Microalga Vischeria punctata in Relation to Cultivation Conditions

by Olga Babich, Ekaterina Budenkova, Egor Kashirskikh, Vyacheslav Dolganyuk, Svetlana Ivanova, Alexander Prosekov, Veronika Anokhova, Anna Andreeva and Stanislav Sukhikh

Life 2022, 12(10), 1614; https://doi.org/10.3390/life12101614 - 15 Oct 2022

Cited by 8 | Viewed by 2270

Abstract

Vischeria punctata is a unicellular microalga that has industrial potential, as it can produce substances with beneficial properties. Among them, endopolysaccharides (accumulated in cells) and exopolysaccharides (released by cells into the culture medium) are of particular interest. This study aimed to investigate the effect of nutrient medium composition on the growth of V. punctata biomass and the synthesis of polysaccharides by microalgae. The effect of modifying a standard nutrient medium and varying cultivation parameters (temperature, time, and extractant type) on the yield of exopolysaccharides produced by the microalgae V. punctate was investigated. The methods of spectrophotometry, ultrasonic extraction, and alcohol precipitation were used in the study. It was found that after 61 days of cultivation, the concentration of polysaccharides in the culture medium was statistically significantly higher (p <0.05) when using a Prat nutrient medium (984.9 mg/g d.w.) than BBM 3N (63.0 mg/g d.w.). It was found that the increase in the V. punctata biomass when cultivated on different nutrient media did not differ significantly. The maximum biomass values on Prat and BBM 3N media were 1.101 mg/g d.w. and 1.120 mg/g d.w., respectively. Neutral sugars and uronic acids were found in the culture media. It follows on from the obtained data that the modified PratM medium was more efficient for extracting polysaccharides from V. punctata. The potential of microalgae as new sources of valuable chemicals (polysaccharides), which can be widely used in technologies for developing novel functional foods, biologically active food supplements, and pharmaceutical substances, was studied. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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18 pages, 2251 KiB

Open AccessArticle

Identification of Metabolites with Antibacterial Activities by Analyzing the FTIR Spectra of Microalgae

by Stanislav Sukhikh, Alexander Prosekov, Svetlana Ivanova, Pavel Maslennikov, Anna Andreeva, Ekaterina Budenkova, Egor Kashirskikh, Anna Tcibulnikova, Evgeniia Zemliakova, Ilia Samusev and Olga Babich

Life 2022, 12(9), 1395; https://doi.org/10.3390/life12091395 - 7 Sep 2022

Cited by 16 | Viewed by 3496

Abstract

Biologically active substances from microalgae can exhibit antioxidant, immunostimulating, antibacterial, antiviral, antitumor, antihypertensive, regenerative, and neuroprotective effects. Lipid complexes of microalgae Chlorella vulgaris and Arthrospira platensis exhibit antibacterial activity and inhibit the growth of the Gram-positive strain Bacillus subtilis; the maximum zone of inhibition is 0.7 ± 0.03 cm at all concentrations. The carbohydrate-containing complex of C. vulgaris exhibits antibacterial activity, inhibits the growth of the Gram-positive strain B. subtilis, Bacillus pumilus; the maximum zone of inhibition is 3.5 ± 0.17 cm at all concentrations considered. The carbohydrate complex of A. platensis has antimicrobial activity against the Gram-negative strain of Escherichia coli at all concentrations, and the zone of inhibition is 2.0–3.0 cm. The presence of mythelenic, carbonyl groups, ester bonds between fatty acids and glycerol in lipid molecules, the stretching vibration of the phosphate group PO₂, neutral lipids, glyco- and phospholipids, and unsaturated fatty acids, such as γ-linolenic, was revealed using FTIR spectra. Spectral peaks characteristic of saccharides were found, and there were cellulose and starch absorption bands, pyranose rings, and phenolic compounds. Both algae in this study had phenolic and alcohol components, which had high antibacterial activity. Microalgae can be used as biologically active food additives and/or as an alternative to antibiotic feed in animal husbandry due to their antibacterial properties. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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24 pages, 2380 KiB

Open AccessArticle

Factorial Optimization of Ultrasound-Assisted Extraction of Phycocyanin from Synechocystis salina: Towards a Biorefinery Approach

by Joana Assunção, Helena M. Amaro, Francisco Xavier Malcata and Ana Catarina Guedes

Life 2022, 12(9), 1389; https://doi.org/10.3390/life12091389 - 6 Sep 2022

Cited by 5 | Viewed by 2536

Abstract

PC is a bioactive and colorant compound widely sought in the food, nutraceutical and cosmetic industries, and one of the most important pigments produced by Synechocystis salina. However, the general extraction process is usually time-consuming and expensive, with low extraction yields—thus compromising a feasible and sustainable bioprocess. Hence, new extraction technologies (e.g., ultrasound assisted-extraction or UAE) emerged in the latest years may serve as a key step to make the overall bioprocess more competitive. Therefore, this study aimed at optimizing the yields of phycocyanin (PC) rich-extracts of S. salina by resorting to UAE; in attempts to explore this process in a more economically feasible way; valorization of the remaining cyanobacterial biomass, via extraction of other bioactive pigments and antioxidants, was tackled within a biorefinery perspective. A two-stage extraction (using ethanol and water) was thus performed (because it favors PC extraction); other bioactive pigments, including chlorophyll a (chl a), carotenoids, and other phycobiliproteins (PBPs), but also antioxidant (AOX) capacity and extraction yields were also evaluated for their optimum UAE yields. A factorial design based on Box–Behnken model was developed; and the influence of such extraction parameters as biomass to solvent ratio (B/S ratio = 1.5–8.5 mg·mL⁻¹), duty cycle (DT = 40–100%), and percentage of amplitude (A = 40–100%) were evaluated. The model predicted higher PC yields with high B/S ratio = 6 mg·mL⁻¹, lower DT = 80% and an A = 100%. Classical extraction was compared with UAE under the optimum conditions found; the latter improved PC yields by 12.5% and 47.8%, when compared to freeze-thawing extraction, and bead beater homogenization-based extraction, respectively. UAE successive extractions allowed to valorize other important bioactive compounds than PC, by reusing biomass, supporting a favorable contribution to the economic feasibility of the S. salina-based process towards a biorefinery approach. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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14 pages, 1798 KiB

Open AccessArticle

Arthrospira platensis Mutagenesis for Protein and C-Phycocyanin Improvement and Proteomics Approaches

by Wanida Pan-utai, Siriluck Iamtham, Sittiruk Roytrakul, Sarn Settachaimongkon, Ladda Sangduean Wattanasiritham, Sumitra Boonbumrung, Juta Mookdasanit and Sayamon Sithtisarn

Life 2022, 12(6), 911; https://doi.org/10.3390/life12060911 - 17 Jun 2022

Cited by 5 | Viewed by 3527

Abstract

Arthrospira (Spirulina) platensis is known for its use as a food supplement, with reported therapeutic properties including antiviral, anti-inflammatory and antioxidant activity. Arthrospira is also an excellent source of proteins and C-phycocyanin. The latter is a light-harvesting pigment-protein complex in cyanobacteria, located on the outer surface of the thylakoid membrane and comprising 40 to 60% of the total soluble protein in cells. Random mutagenesis is a useful tool as a non-genetically modified mutation method that has been widely used to generate mutants of different microorganisms. Exposure of microalgae or cyanobacteria to chemical stimuli affects their growth and many biological processes. Chemicals influence several proteins, including those involved in carbohydrate and energy metabolisms, photosynthesis and stress-related proteins (oxidative stress-reactive oxygen species (ROS) scavenging enzymes). Signal transduction pathways and ion transportation mechanisms are also impacted by chemical treatment, with changes causing the production of numerous biomolecules and stimulation of defence responses. This study compared the protein contents of A. platensis control and after mutagenesis using diethyl sulphate (DES) under various treatment concentrations for effective mutation of A. platensis. Results identified 1152 peptides using proteomics approaches. The proteins were classified into 23 functional categories. Random mutagenesis of A. platensis by DES was found to be highly effective for C-phycocyanin and protein production. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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20 pages, 4370 KiB

Open AccessArticle

The Effect of Colored and White Light on Growth and Phycobiliproteins, Chlorophyll and Carotenoids Content of the Marine Cyanobacteria Phormidium sp. and Cyanothece sp. in Batch Cultures

by George N. Hotos and Theodoros I. Antoniadis

Life 2022, 12(6), 837; https://doi.org/10.3390/life12060837 - 4 Jun 2022

Cited by 16 | Viewed by 4147

Abstract

Two local marine cyanobacteria, Phormidium sp. and Cyanothece sp., were batch-cultured under 18–19.5 °C, at 40 ppt salinity, using white LED light of low (40 μmol photons/m²/s) and high (160 μmol/m²/s) intensity and, additionally, blue, green and red LED light. Yield was highest in high white light in both species (2.15 g dw/L in Phormidium, 1.47 g/L in Cyanothece), followed by green light (1.25 g/L) in Cyanothece and low white and green (1.26–1.33 g/L) in Phormidium. Green light maximized phycocyanin in Phormidium (0.45 mg/mL), while phycoerythrin was enhanced (0.17 mg/mL) by blue light and allophycocyanin by all colors (~0.80 mg/mL). All colors maximized phycocyanin in Cyanothece (~0.32 mg/mL), while phycoerythrin and allophycocyanin peaked under green light (~0.138 and 0.38 mg/mL, respectively). In Phormidium, maximization of chlorophyll-a (9.3 μg/mL) was induced by green light, while total carotenoids and b-carotene (3.05 and 0.89 μg/mL, respectively) by high white light. In Cyanothece, both white light intensities along with green maximized chlorophyll-a (~9 μg/mL) while high white light and green maximized total carotenoids (2.6–3.0 μg/mL). This study strongly indicates that these cyanobacteria can be cultured at the first stage under white light to accumulate sufficient biomass and, subsequently, under colored light for enhancing phycobiliproteins. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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15 pages, 2515 KiB

Open AccessArticle

Microalgae Peptide-Stabilized Gold Nanoparticles as a Versatile Material for Biomedical Applications

by Marielys Torres-Díaz, Caren Abreu-Takemura and Liz M. Díaz-Vázquez

Life 2022, 12(6), 831; https://doi.org/10.3390/life12060831 - 2 Jun 2022

Cited by 4 | Viewed by 2720

Abstract

Microalgae peptides have many medical and industrial applications due to their functional properties. However, the rapid degradation of peptides not naturally present in biological samples represents a challenge. A strategy to increase microalgae peptide stability in biological samples is to use carriers to protect the active peptide and regulate its release. This study explores the use of gold nanoparticles (AuNPs) as carriers of the Chlorella microalgae peptide (VECYGPNRPQF). The potential of these peptide biomolecules as stabilizing agents to improve the colloidal stability of AuNPs in physiological environments is also discussed. Spectroscopic (UV-VIS, DLS) and Microscopic (TEM) analyses confirmed that the employed modification method produced spherical AuNPs by an average 15 nm diameter. Successful peptide capping of AuNPs was confirmed with TEM images and FTIR spectroscopy. The stability of the microalgae peptide increased when immobilized into the AuNPs surface, as confirmed by the observed thermal shifts in DSC and high zeta-potential values in the colloidal solution. By optimizing the synthesis of AuNPs and tracking the conferred chemical properties as AuNPs were modified with the peptide via various alternative methods, the synthesis of an effective peptide-based coating system for AuNPs and drug carriers was achieved. The microalgae peptide AuNPs showed lower ecotoxicity and better viability than the regular AuNPs. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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20 pages, 2419 KiB

Open AccessArticle

The Role of Photo-Cycles in the Modulation of Growth and Biochemical Profile of Microalgae: Part I—Food Interest Compounds

by Rafaela Basso Sartori, Raquel Guidetti Vendruscolo, Stephanie Reis Ribeiro, Valcenir Júnior Mendes Furlan, Roger Wagner, Leila Queiroz Zepka and Eduardo Jacob-Lopes

Life 2022, 12(3), 462; https://doi.org/10.3390/life12030462 - 21 Mar 2022

Cited by 5 | Viewed by 2470

Abstract

The objective of this work was to evaluate the effect of different photo-cycles on the growth and biochemical profile of Scenedesmus obliquus CPCC05, focusing on food interest compounds. The photo-cycle conditions were separated into three groups: long-term photo-cycles (24:0, 22:2, 20:4, 18:6, 12:12, and 10:14 (h:h)), frequency photo-cycles (2, 4, 8, 12, 24, and 48 times per day (t/d)), and short photo-cycles (0.91:0.09, 0.83:0.17, 0.75:0.25, and 0.50:0.50 (s:s)) of light:dark, respectively. The results showed these microalgae can store enough energy to support cell growth for continuous periods of up to 2 h in the dark, without affecting the productivity of the process. This 2 h, when divided into 2 cycles per day (2 t/d), showed the best growth condition (3700 mg L⁻¹), generation time (14.40 h), and maximum biomass productivity (21.43 mg L h⁻¹). This photo-cycle of 2 t/d was also the best condition for the production of total sterols. However, the values of polyunsaturated fatty acids, lipid content, and amino acids obtained higher yields in the short photo-cycle of 0.75:0.25. Thus, the modulation of light cycles becomes an important tool for boosting and directing the production of target molecules in phototrophic cultures of microalgae. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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21 pages, 16319 KiB

Open AccessArticle

A Fast-Growing Oleaginous Strain of Coelastrella Capable of Astaxanthin and Canthaxanthin Accumulation in Phototrophy and Heterotrophy

by Amélie Corato, Thanh Tung Le, Denis Baurain, Philippe Jacques, Claire Remacle and Fabrice Franck

Life 2022, 12(3), 334; https://doi.org/10.3390/life12030334 - 23 Feb 2022

Cited by 13 | Viewed by 3306

Abstract

Considering the importance of microalgae as a promising feedstock for the production of both low- and high-value products, such as lipids and pigments, it is desirable to isolate strains which simultaneously accumulate these two types of products and grow in various conditions in order to widen their biotechnological applicability. A novel freshwater strain from the genus Coelastrella was isolated in Belgium. Compared to other Coelastrella species, the isolate presented rapid growth in phototrophy, dividing 3.5 times per day at a light intensity of 400 µmol·m⁻²·s⁻¹ and 5% CO₂. In addition, nitrogen depletion was associated with the accumulation of astaxanthin, canthaxanthin, and fatty acids, which reached ~30% of dry weight, and a majority of SFAs and MUFAs, which are good precursors for biodiesel. This strain also accumulated astaxanthin and canthaxanthin in heterotrophy. Although the content was very low in this latter condition, it is an interesting feature considering the biotechnological potential of the microalgal heterotrophic growth. Thus, due to its rapid growth in the light, its carotenogenesis, and its fatty acids characteristics, the newly identified Coelastrella strain could be considered as a potential candidate for biorefinery purposes of both low- and high-values products. Full article

(This article belongs to the Special Issue Microalgae Metabolites)

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