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14 pages, 1162 KiB

Open AccessArticle

Improvement of Chemical Composition of Tisochrysis lutea Grown Mixotrophically under Nitrogen Depletion towards Biodiesel Production

by Adel W. Almutairi

Molecules 2020, 25(20), 4609; https://doi.org/10.3390/molecules25204609 - 10 Oct 2020

Cited by 18 | Viewed by 2964

Abstract

In the present study, the marine microalga Tisochrysis lutea was cultivated mixotrophically in F2 growth medium with sodium acetate as exogenous carbon source. The medium was composed of different concentrations of nitrogen to determine the impact of nitrogen depletion on cellular growth and [...] Read more.

In the present study, the marine microalga Tisochrysis lutea was cultivated mixotrophically in F2 growth medium with sodium acetate as exogenous carbon source. The medium was composed of different concentrations of nitrogen to determine the impact of nitrogen depletion on cellular growth and chemical composition. Nitrogen depletion led to severely decreased growth and protein content. However, mild nitrogen depletion (0.22 mM NaNO₃) led to maximum lipid yield. The fatty acid methyl ester profile also showed increased unsaturation as the nitrogen content decreased. Growth in nitrogen-free medium increased the proportions of mono- and poly-unsaturated fatty acids, while the proportion of saturated fatty acids decreased. Growth under all tested nitrogen levels showed undetectable fatty acids with ≥4 double bonds, indicating these fatty acids had oxidative stability. In addition, all tested nitrogen concentrations led to specific gravity, kinematic viscosity, iodine value, and cetane number that meet the standards for Europe and the U.S.A. However, growth in the presence of nitrogen deficiency enhanced the higher heating value of the resulting biodiesel, a clear advantage from the perspective of energy efficiency. Thus, mixotrophic cultivation of T. lutea with nitrogen limitation provides a promising approach to achieve high lipid productivity and production of high-quality biodiesel. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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16 pages, 1222 KiB

Open AccessArticle

Impacts of Endocrine Disruptor di-n-Butyl Phthalate Ester on Microalga Chlorella vulgaris Verified by Approaches of Proteomics and Gene Ontology

by Chien-Sen Liao, Yong-Han Hong, Yoshikazu Nishikawa, Eriko Kage-Nakadai, Tai-Ying Chiou and Chien-Chang Wu

Molecules 2020, 25(18), 4304; https://doi.org/10.3390/molecules25184304 - 19 Sep 2020

Cited by 3 | Viewed by 2550

Abstract

Di-n-butyl phthalate (DBP) is an extensively used plasticizer. Most investigations on DBP have been concentrated on its environmental distribution and toxicity to humans. However, information on the effects of plasticizers on algal species is scarce. This study verified the impacts of [...] Read more.

Di-n-butyl phthalate (DBP) is an extensively used plasticizer. Most investigations on DBP have been concentrated on its environmental distribution and toxicity to humans. However, information on the effects of plasticizers on algal species is scarce. This study verified the impacts of endocrine disruptor di-n-butyl phthalate ester on microalga Chlorella vulgaris by approaches of proteomics and gene ontology. The algal acute biotoxicity results showed that the 24h-EC50 of DBP for C. vulgaris was 4.95 mg L⁻¹, which caused a decrease in the chlorophyll a content and an increase in the DBP concentration of C. vulgaris. Proteomic analysis led to the identification of 1257 C. vulgaris proteins. Sixty-one more proteins showed increased expression, compared to proteins with decreased expression. This result illustrates that exposure to DBP generally enhances protein expression in C. vulgaris. GO annotation showed that both acetolactate synthase (ALS) and GDP-L-fucose synthase 2 (GER2) decreased more than 1.5-fold after exposure to DBP. These effects could inhibit both the valine biosynthetic process and the nucleotide-sugar metabolic process in C. vulgaris. The results of this study demonstrate that DBP could inhibit growth and cause significant changes to the biosynthesis-relevant proteins in C. vulgaris. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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16 pages, 1924 KiB

Open AccessArticle

Continuous Microalgal Cultivation for Antioxidants Production

by Jenny Fabiola López-Hernández, Pedro García-Alamilla, Diana Palma-Ramírez, Carlos Alfonso Álvarez-González, Juan Carlos Paredes-Rojas and Facundo J. Márquez-Rocha

Molecules 2020, 25(18), 4171; https://doi.org/10.3390/molecules25184171 - 11 Sep 2020

Cited by 25 | Viewed by 3733

Abstract

Microalgae, including cyanobacteria, represent a valuable source of natural compounds that have remarkable bioactive properties. Each microalga species produces a mixture of antioxidants with different amounts of each compound. Three aspects are important in the production of bioactive compounds: the microalga species, the [...] Read more.

Microalgae, including cyanobacteria, represent a valuable source of natural compounds that have remarkable bioactive properties. Each microalga species produces a mixture of antioxidants with different amounts of each compound. Three aspects are important in the production of bioactive compounds: the microalga species, the medium composition including light supplied and the photobioreactor design, and operation characteristics. In this study, the antioxidant content and productivity performance of four microalgae were assessed in batch and continuous cultures. Biomass productivity by the four microalgae was substantially enhanced under continuous cultivation by 5.9 to 6.3 times in comparison with batch cultures. The energetic yield, under the experimental conditions studied, ranged from 0.03 to 0.041 g biomass kJ⁻¹. Phenols, terpenoids, and alkaloids were produced by Spirulinaplatensis, Isochrysisgalbana, and Tetraselmissuecica, whereas tocopherols and carotenoids were produced by the four microalgae, except for phycocyanin and allophycocyanin, which were only produced by S. platensis and Porphyridiumcruentum. The findings demonstrate that the continuous cultivation of microalgae in photobioreactors is a convenient method of efficiently producing antioxidants. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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15 pages, 4014 KiB

Open AccessArticle

Stereoisomers of Colourless Carotenoids from the Marine Microalga Dunaliella salina

by Laura Mazzucchi, Yanan Xu and Patricia Harvey

Molecules 2020, 25(8), 1880; https://doi.org/10.3390/molecules25081880 - 18 Apr 2020

Cited by 13 | Viewed by 4651

Abstract

Carotenoids comprise a diverse range of naturally occurring stereoisomers, which differ in their physico-chemical properties. Their biosynthesis begins with phytoene, which is a rarity among carotenoids because it is colourless. Phytoene is sought after as a skin protectant against harmful UV range B [...] Read more.

Carotenoids comprise a diverse range of naturally occurring stereoisomers, which differ in their physico-chemical properties. Their biosynthesis begins with phytoene, which is a rarity among carotenoids because it is colourless. Phytoene is sought after as a skin protectant against harmful UV range B (290–320 nm) and C (100–290 nm) light, and as a natural skin-whitening agent and is synthesized from geranylgeranyl diphosphate. Geranylgeranyl diphosphate is catalysed by phytoene synthase and phytoene desaturase to phytoene and phytofluene, respectively. The subsequent steps involve desaturation, isomerisation and cyclisation reactions to form α- and β-carotene stereoisomers, via all-trans lycopene. The marine microalga Dunaliella salina is the richest source of β-carotene, but it can accumulate phytoene and phytofluene as well. In the present study, different analytical tools including High-Performance Liquid Chromatography (HPLC), Ultra-Performance Convergence Chromatography (UPC²-MS) and Nuclear Magnetic Resonance (NMR) were used to characterize and quantify the phytoene isomeric configurations in D. salina in order to explore both the feasibility of D. salina as a cell factory for phytoene production and to gain new insight into the carotenoid synthesis pathway in D. salina. D. salina, similar to tomato, produced predominantly 15-cis phytoene isomer (>98%) and a trace amount of all-trans phytoene (<2%). High light stress, red light stress, or use of a phytoene desaturase inhibitor or a mitotic disrupter herbicide led to the accumulation of 15-cis phytoene but not all-trans phytoene. 9-cis phytoene was not detected in any of the extracts of D. salina biomass. Our main findings suggest that 15-cis phytoene is the most abundant isomer in D. salina and that it is subject to a series of isomerisation and desaturation reactions to form all-trans and 9-cis β-carotene. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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17 pages, 1150 KiB

Open AccessArticle

Determining the Potential of Haematococcus pluvialis Oleoresin as a Rich Source of Antioxidants

by Mari Carmen Ruiz-Domínguez, Carolina Espinosa, Adrián Paredes, Jenifer Palma, Carolina Jaime, Carlos Vílchez and Pedro Cerezal

Molecules 2019, 24(22), 4073; https://doi.org/10.3390/molecules24224073 - 11 Nov 2019

Cited by 25 | Viewed by 4549

Abstract

Haematococcus pluvialis is known to be a natural source of antioxidants for numerous applications. In this study, an oleoresin rich in carotenoids extracted by supercritical CO₂ treatment of H. pluvialis was extensively characterized for its antioxidant capacity. Carotenoid content, fatty acid profile, [...] Read more.

Haematococcus pluvialis is known to be a natural source of antioxidants for numerous applications. In this study, an oleoresin rich in carotenoids extracted by supercritical CO₂ treatment of H. pluvialis was extensively characterized for its antioxidant capacity. Carotenoid content, fatty acid profile, total phenol content, antioxidant capacity, and viscosity of the oleoresin were determined with the aim of ascertaining the potential of the oleoresin in terms of its antioxidant content for food applications. The oleoresin contained 96.22 mg/g of total astaxanthin (which includes free astaxanthin and astaxanthin esters) and mostly included unsaturated fatty acids (~78% of total fatty acids). High total phenol content and ferric reducing antioxidant potential indicated high antioxidant capacity, but oxygen radical absorbance capacity was lower compared to the oleoresin samples obtained from other species. The oleoresin was a non-Newtonian fluid since it had shear-thinning (pseudoplastic) and shear-thickening (dilatant) flow. Therefore, the H. pluvialis oleoresin is a potential alternative in developing functional ingredients for designing healthy food products. To the best of our knowledge, this is the first study that has reported an extensive characterization of the antioxidant properties of a microalgal oleoresin obtained by means of supercritical CO₂ fluid extraction. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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Review

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45 pages, 2508 KiB

Open AccessReview

Isolation of Industrial Important Bioactive Compounds from Microalgae

by Vimala Balasubramaniam, Rathi Devi-Nair Gunasegavan, Suraiami Mustar, June Chelyn Lee and Mohd Fairulnizal Mohd Noh

Molecules 2021, 26(4), 943; https://doi.org/10.3390/molecules26040943 - 10 Feb 2021

Cited by 85 | Viewed by 9556

Abstract

Microalgae are known as a rich source of bioactive compounds which exhibit different biological activities. Increased demand for sustainable biomass for production of important bioactive components with various potential especially therapeutic applications has resulted in noticeable interest in algae. Utilisation of microalgae in [...] Read more.

Microalgae are known as a rich source of bioactive compounds which exhibit different biological activities. Increased demand for sustainable biomass for production of important bioactive components with various potential especially therapeutic applications has resulted in noticeable interest in algae. Utilisation of microalgae in multiple scopes has been growing in various industries ranging from harnessing renewable energy to exploitation of high-value products. The focuses of this review are on production and the use of value-added components obtained from microalgae with current and potential application in the pharmaceutical, nutraceutical, cosmeceutical, energy and agri-food industries, as well as for bioremediation. Moreover, this work discusses the advantage, potential new beneficial strains, applications, limitations, research gaps and future prospect of microalgae in industry. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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23 pages, 1168 KiB

Open AccessReview

Processing Methodologies of Wet Microalga Biomass Toward Oil Separation: An Overview

by Vânia Pôjo, Tânia Tavares and Francisco Xavier Malcata

Molecules 2021, 26(3), 641; https://doi.org/10.3390/molecules26030641 - 26 Jan 2021

Cited by 15 | Viewed by 5160

Abstract

One of the main goals of Mankind is to ensure food system sustainability—including management of land, soil, water, and biodiversity. Microalgae accordingly appear as an innovative and scalable alternative source in view of the richness of their chemical profiles. In what concerns lipids [...] Read more.

One of the main goals of Mankind is to ensure food system sustainability—including management of land, soil, water, and biodiversity. Microalgae accordingly appear as an innovative and scalable alternative source in view of the richness of their chemical profiles. In what concerns lipids in particular, microalgae can synthesize and accumulate significant amounts of fatty acids, a great fraction of which are polyunsaturated; this makes them excellent candidates within the framework of production and exploitation of lipids by various industrial and health sectors, either as bulk products or fine chemicals. Conventional lipid extraction methodologies require previous dehydration of microalgal biomass, which hampers economic feasibility due to the high energy demands thereof. Therefore, extraction of lipids directly from wet biomass would be a plus in this endeavor. Supporting processes and methodologies are still limited, and most approaches are empirical in nature—so a deeper mechanistic elucidation is a must, in order to facilitate rational optimization of the extraction processes. Besides circumventing the current high energy demands by dehydration, an ideal extraction method should be selective, sustainable, efficient, harmless, and feasible for upscale to industrial level. This review presents and discusses several pretreatments incurred in lipid extraction from wet microalga biomass, namely recent developments and integrated processes. Unfortunately, most such developments have been proven at bench-scale only—so demonstration in large facilities is still needed to confirm whether they can turn into competitive alternatives. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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27 pages, 624 KiB

Open AccessReview

Cyanobacteria and Eukaryotic Microalgae as Emerging Sources of Antibacterial Peptides

by Verónica Rojas, Luis Rivas, Constanza Cárdenas and Fanny Guzmán

Molecules 2020, 25(24), 5804; https://doi.org/10.3390/molecules25245804 - 9 Dec 2020

Cited by 63 | Viewed by 6449

Abstract

Cyanobacteria and microalgae are oxygen-producing photosynthetic unicellular organisms encompassing a great diversity of species, which are able to grow under all types of extreme environments and exposed to a wide variety of predators and microbial pathogens. The antibacterial compounds described for these organisms [...] Read more.

Cyanobacteria and microalgae are oxygen-producing photosynthetic unicellular organisms encompassing a great diversity of species, which are able to grow under all types of extreme environments and exposed to a wide variety of predators and microbial pathogens. The antibacterial compounds described for these organisms include alkaloids, fatty acids, indoles, macrolides, peptides, phenols, pigments and terpenes, among others. This review presents an overview of antibacterial peptides isolated from cyanobacteria and microalgae, as well as their synergism and mechanisms of action described so far. Antibacterial cyanopeptides belong to different orders, but mainly from Oscillatoriales and Nostocales. Cyanopeptides have different structures but are mainly cyclic peptides. This vast peptide repertoire includes ribosomal and abundant non-ribosomal peptides, evaluated by standard conventional methodologies against pathogenic Gram-negative and Gram-positive bacteria. The antibacterial activity described for microalgal peptides is considerably scarcer, and limited to protein hydrolysates from two Chlorella species, and few peptides from Tetraselmis suecica. Despite the promising applications of antibacterial peptides and the importance of searching for new natural sources of antibiotics, limitations still persist for their pharmaceutical applications. Full article

(This article belongs to the Special Issue Bioactive Compounds Isolated from Microalgae)

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