Red Microalga Porphyridium Research Articles

Enhancing total fatty acids and arachidonic acid production by the red microalgae Porphyridium purpureum

This study investigated the effect of aeration rate and light intensity on biomass production and total fatty acids (TFA) accumulation by Porphyridium purpureum. The red microalgae is also known to accumulate considerable amount of arachidonic acid (ARA). In artificial seawater medium, the highest yield of TFA (473.44 mg/L) was obtained with the aeration rate of 3 L/min and light intensity of 165 µmol/m2s, whilst the highest yield of ARA (115.47 mg/L) was achieved with the aeration rate of 3 L/min and light intensity of 110 µmol/m2s. It was found that higher aeration rate led to more biomass and TFA/ARA production. However, higher light intensity could contribute to biomass accumulation, but it was adverse for TFA and ARA biosynthesis. By optimizing two operating factors (i.e., light intensity and aeration rate), TFA and ARA production by P. purpureum was significantly improved. This research provides a potential alternative means for producing ARA.

Insight into glucosidase II from the red marine microalga Porphyridium sp. (Rhodophyta).

N-glycosylation of proteins is one of the most important post-translational modifications that occur in various organisms, and is of utmost importance for protein function, stability, secretion, and loca-lization. Although the N-linked glycosylation pathway of proteins has been extensively characterized in mammals and plants, not much information is available regarding the N-glycosylation pathway in algae. We studied the α 1,3-glucosidase glucosidase II (GANAB) glycoenzyme in a red marine microalga Porphyridium sp. (Rhodophyta) using bioinformatic and biochemical approaches. The GANAB-gene was found to be highly conserved evolutionarily (compo-sed of all the common features of α and β subunits) and to exhibit similar motifs consistent with that of homolog eukaryotes GANAB genes. Phylogenetic analysis revealed its wide distribution across an evolutionarily vast range of organisms; while the α subunit is highly conserved and its phylogenic tree is similar to the taxon evolutionary tree, the β subunit is less conserved and its pattern somewhat differs from the taxon tree. In addition, the activity of the red microalgal GANAB enzyme was studied, including functional and biochemical characterization using a bioassay, indicating that the enzyme is similar to other eukaryotes ortholog GANAB enzymes. A correlation between polysaccharide production and GANAB activity, indicating its involvement in polysaccharide biosynthesis, is also demonstrated. This study represents a valuable contribution toward understanding the N-glycosylation and polysaccharide biosynthesis pathways in red microalgae.

Genes Involved in the Endoplasmic Reticulum N-Glycosylation Pathway of the Red Microalga Porphyridium sp.: A Bioinformatic Study

N-glycosylation is one of the most important post-translational modifications that influence protein polymorphism, including protein structures and their functions. Although this important biological process has been extensively studied in mammals, only limited knowledge exists regarding glycosylation in algae. The current research is focused on the red microalga Porphyridium sp., which is a potentially valuable source for various applications, such as skin therapy, food, and pharmaceuticals. The enzymes involved in the biosynthesis and processing of N-glycans remain undefined in this species, and the mechanism(s) of their genetic regulation is completely unknown. In this study, we describe our pioneering attempt to understand the endoplasmic reticulum N-Glycosylation pathway in Porphyridium sp., using a bioinformatic approach. Homology searches, based on sequence similarities with genes encoding proteins involved in the ER N-glycosylation pathway (including their conserved parts) were conducted using the TBLASTN function on the algae DNA scaffold contigs database. This approach led to the identification of 24 encoded-genes implicated with the ER N-glycosylation pathway in Porphyridium sp. Homologs were found for almost all known N-glycosylation protein sequences in the ER pathway of Porphyridium sp.; thus, suggesting that the ER-pathway is conserved; as it is in other organisms (animals, plants, yeasts, etc.).

Bioaccumulation of Pb, Cd, Cu, and Cr by <i>Porphyridium cruentum</i> (S.F. Gray) Nägeli

The red microalgae Porphyridium cruentum (S.F. Gray) Nageli usually was used as feeds, a pigment for food and cosmetic, and antiviral activity that might be became industrial interest. Similar to another microalgae, P. cruentum has an ability to remediate heavy metals pollution, however research on it still limited. This research was conducted in order to find out the the accumulation of Pb, Cd, Cr, and Cu on the P. cruentum . A laboratory experiment were developed with different concentrations. Based on this research, P. cruentum with the treatment of 1 mg/L had reduced higher Cu, Pb, Cd, and Cr concentrations rather than 3 and 5 mg/L concentrations, respectively. This was also similar to the BCF, that in day 8 in order of Cu > Cr > Cd > Pb, respectively; however, in day 15 was Cu > Pb > Cd > Cr. The length of treatment influenced BCF value. P. cruentum was good for bioremediation of heavy metal pollution, with the advantage of the short of accumulation time.

Evaluation of the protein quality of Porphyridium cruentum

The amino acid profile of the red microalga Porphyridium cruentum and its protein extract have been determined in order to assess the nutritional quality of this biomass for human consumption. Total protein determined by elemental analysis represented 56 % of its dry weight. Hydro-soluble proteins extracted at pH 12 and 40 °C were analysed by the Lowry method giving 47 %, which represented 84 % of total protein per dry weight. The amino acid sequence of the biomass and the protein extract was composed of a set of essential (39 % for the former and 37 % for the latter) and non-essential amino acids (61 % for the former and 63 % for the latter) that compares favourably with the standard protein/amino acid requirements proposed by Food and Agricultural Organisation and World Health Organisation.

Increased production of extracellular polysaccharide byPorphyridium cruentumimmobilized in foam sheets

AbstractLarge‐size plate bioreactors were used to compare the production of extracellular polysaccharide by the red microalgaPorphyridium cruentumwhen grown in suspension and in a foam sheet. A well‐defined illuminated area and unidirectional light propagation allowed us to generate information that is better quantified when expressed in terms of illuminated area. This is essential for meaningful comparison of data, especially considering that for a well‐designed and managed bioreactor, the culture production rates are believed to be light limited. At the same level of illumination, the culture immobilized in foam showed double the production rate of extracellular polysaccharide compared with the culture in suspension. The saturation level of biomass densityperunit of illuminated area was eight times higher for the immobilized culture compared with the culture in suspension. Despite the increased biomass density for the immobilized culture, an increase in the light level above the optimum found for the culture in suspension reduced the extracellular polysaccharide production, suggesting that the photoinhibition light level was surpassed.

Hypocholesterolemic Effects of Nutraceuticals Produced from the Red Microalga Porphyridium sp. in Rats

Red microalgae contain functional sulfated polysaccharides (containing dietary fibers), polyunsaturated fatty acids, zeaxanthin, vitamins, minerals, and proteins. Studies in rat models support the therapeutic properties of algal biomass and isolated polysaccharides. Algal products incorporated into rat diets were found to significantly improve total serum cholesterol, serum triglycerides, hepatic cholesterol levels, HDL/LDL ratios and increased fecal excretion of neutral sterols and bile acids. Morphological and metabolic changes were induced by consumption of algal products. These results suggest that red microalgae can be used as potent hypocholesterolemic agents, and they support the potential use of red microalgae as novel nutraceuticals.

Effect of Brefeldin A on cell-wall polysaccharide production in the red microalga Porphyridium sp. (Rhodophyta) through its effect on the Golgi apparatus

The cells of the red microalga Porphyridium sp. are encapsulated within a complex sulphated polysaccharide, comprising cell-wall-bound and soluble fractions. The current study investigated the involvement of the Golgi apparatus in the production of the sulphated polysaccharide by treating the cultures with brefeldin A (BFA), a membrane-traffic inhibitor of the Golgi apparatus. Addition of BFA (10–25 μM) upon inoculation (logarithmic-phase cells) decreased the contents of both bound and soluble polysaccharides. Exposure of stationary-phase cultures to BFA (20 μM) inhibited the formation of the cell-wall bound polysaccharide to a greater extent than that of the soluble polysaccharide. Under conditions of nitrate starvation, BFA treatment had a more marked effect on soluble than on bound polysaccharide formation, as was supported by 14C pulse-chase experiments. BFA addition up to the first 10 h of the cell cycle affected cell division and bound polysaccharide and starch contents. An ultrastructural study showed that exposure of the cells to 20 μM BFA for 16 h disrupted the integrity of the Golgi apparatus. The integrated results of this study demonstrate clearly that BFA affects the architecture of the Golgi apparatus and hence polysaccharide production in algal cells.

Cancer Protective Action of Polysaccharide, Derived from Red Microalga Porphyridium Cruentum—A Biological Background

ABSTRACTThe cell wall sulfated polysaccharide of the red microalga Porphyridium cruentum (Rhodophyta) (PcrPSH) exhibited strong antitumor activity against Graffi myeloid tumor in hamsters both in vitro and in vivo. When tested in vivo, depending on the concentration and the way of application, this polysaccharide decreased transplantability in all experimental groups till 20 days of observation and mortality rate. The tumor growth was retarded and the mean survival time was prolonged with 10 - 16 days. Applied in in vitro experiments the PcrPSH increased both—spreading and phagocytic ability of peritoneal macrophages from healthy and Graffi tumor bearing hamsters in a dose—dependent manner. Primary Graffi tumor cell culture, cultivated in the presence of PcrPSH showed significant decrease of cell viability, determined by MTT test, while in cells derived from bone marrow it was increased at the same conditions of cultivation and concentration of polysaccharide. Primary Graffi tumor cell culture, treated with PcrPSH showed the appearance of a characteristic DNA ladder on agarose gel electrophoresis, which is a biochemical hallmark of apoptosis. The manifested anticancer activity of PcrPSH could be associated with its immunostimulating action as well as with direct cytotoxic properties. Based on these results, we could suggest that the tested algal PcrPSH is a promising candidate as an antitumor agent. Further studies will be done to clarify the mechanisms of a biological action of PcrPSH.

Isolation and characterization of poly- and oligosaccharides from the red microalga Porphyridium sp.

The current study forms part of an ongoing research effort focusing on the elucidation of the chemical structure of the sulfated extracellular polysaccharide of the red microalga Porphyridium sp. (UTEX 637). We report here on the chemical structure of a fraction separated from an acidic crude extract of the polysaccharide, as investigated by methylation analysis, carboxyl reduction–methylation analysis, desulfation–methylation analysis, partial acid hydrolysis, Smith degradation, together with 1D and 2D 1H and 13C NMR spectroscopy. This fraction with a molar mass of 2.39 × 10 5 g mol −1 comprised d- and l-Gal, d-Glc, d-Xyl, d-GlcA, and sulfate groups in a molar ratio of 1.0:1.1:2.1:0.2:0.7. The almost linear backbone of the fraction is composed of (1→2)- or (1→4)-linked d-xylopyranosyl, (1→3)-linked l-galactopyranosyl, (1→3)-linked d-glucopyranosyl, and (1→3)-linked d-glucopyranosyluronic acid and comprises a possible acidic building unit: [(2 or 4)-β- d-Xyl p-(l→3)] m -α- d-Glc p-(1→3)-α- d-Glc pA-(1→3)- l-Gal p(l→ Attached to the backbone are sulfate groups and nonreducing terminal d-xylopyranosyl and galactopyranosyl residues, which occur at the O-6 positions of Glc-derived moieties in the main chain.

Effect of dietary administration of Porphyridium cruentum on the respiratory burst activity of sole, Solea senegalensis (Kaup), phagocytes

The stimulatory effect of the red microalga Porphyridium cruentum on respiratory burst activity of sole phagocytes was evaluated in vivo. Oral administration of a diet supplemented with lyophilized P. cruentum cells (10 g kg(-1)) stimulated respiratory burst activity after 4 weeks feeding in sole vaccinated with Photobacterium damselae subsp. piscicida bacterin.

The Use of Carrier Ampholyte-Free Isoelectric Focusing for Proteomic Analysis

Carrier ampholyte-free isoelectric focusing was applied for pre-concentration, purification and micropreparation of phycobiliproteins (C-phycocyanin, allophycocyanin, B-phycoerythrin) extracted from cyanobacteria Anabeana doliolum and from red microalga Porphyridium cruentum. The extraction of phycobiliproteins was carried out in deionized water. The sonication in the ultrasonic bath and liquid nitrogen freeze grind was used for extraction of proteins of interest. Pre-concentrated and pre-separated proteins were collected and analyzed via MALDI-TOF-TOF mass spectrometer after their proteolytic digestion via trypsin. Based on tandem mass spectrometric analysis, the C-phycocyanin, allophycocyanin and B-phycoerythrin were identified unambiguously.

Effect of drying on the biological activities of a red microalgal polysaccharide

The red microalga Porphyridium sp. produces a polysaccharide exhibiting a variety of biological activities with potential for medical and cosmetic uses. For this reason, it is important that the drying process, which is the end point of production, should not destroy the natural characteristics of the material. The objective of this study was to evaluate the effect of drying at temperatures ranging from 40 to 140 degrees C on the bioactivities of the polysaccharide. Drying the polysaccharide at temperatures above 90 degrees C caused a significant decline in its biological activities (antiviral and anti-cell proliferation) and reduced elasticity, viscosity, and intrinsic viscosity relative to lyophilized polysaccharide and to the starting product. The relationship between molecular weight and intrinsic viscosity indicated that the polysaccharide takes a rigid coil conformation, which stiffens as a result of drying. FTIR analysis revealed that drying caused both significant conformational alterations in the polymer chains and changes in the interaction between the polysaccharide and the glycoprotein to which it is noncovalently associated. Differential scanning calorimetry analysis of the water adsorbed on the charged groups of the polysaccharide showed that drying at higher temperatures increased the bound water content due to dissociation of the polymer chains. Thus, it is recommended that the polysaccharide be dried in a two-step process in which free water is removed by convection and bound freezing water is removed by lyphophilization.

Inhibition of the growth of the red microalga porphyridium sp. by limitation of nutrient transfer

The unicellular red alga Porphyridium sp. was cultured in a medium to which increasing concentrations of its cell wall polysaccharide were added. As the polysaccharide concentration in the culture medium increased, algal growth rate and maximum cell number progressively decreased. In a different series of experiments it was shown that the polysaccharide also inhibited the rate of carbon uptake by the cells and as a result photosynthesis was also inhibited. In-vitro experiments showed that the mass transfer coefficient for nitrate, bicarbonate, phosphate and potassium decreased as the polysaccharide concentration increased. The data indicate that the polysaccharide inhibits nutrient transfer from the medium to the cells, resulting in a reduction of the growth rate.

Optimization of culturing conditions of Porphyridium cruentum using uniform design

The red microalga Porphyridium contains many valuable compounds such as polysaccharides, polyunsaturated fatty acids, and phycoerythrin (PE). In this study, a uniform design method and regression analysis were used to investigate the effects of initial pH, light intensity, inoculation ratio, and liquid volume in flask on the optimal biomass, exopolysaccharides (EPS), and PE production of Porphyridium cruentum in a batch culture at laboratory scale. Using regression analysis, we obtained the models to clarify the effects of individual factors and their interactions on the biomass, EPS, and PE production of P. cruentum. The optimal condition for the biomass was the following: pH 5.0, light intensity 7098.0 lx, inoculation ratio 1:17.2, and liquid volume 100.0 ml; for EPS was pH 5.0, light intensity 4501.0 lx, inoculation ratio 1:20, and liquid volume 100.3 ml; while pH 8.0, light intensity 7100.0 lx, inoculation ratio 1:20, and liquid volume 100.3 ml was the best for PE production. The maximum biomass 3.27 g/l, EPS production 543.1 mg/l, and PE production 132.0 mg/l were demonstrated by confirmatory experiment to the optimum culture conditions in a reciprocal shaker. The statistical methods used in the present study are useful strategies for optimizing of culture conditions for other microalgae.

Assimilation of sulphur into the cell-wall polysaccharide of the red microalga Porphyridium sp. (Rhodophyta)

M. Keidan, H. Broshy, D. van Moppes and S. (Malis) Arad. 2006. Assimilation of sulphur into the cell-wall polysaccharide of the red microalga Porphyridium sp. (Rhodophyta). Phycologia 45: 505–511. DOI: 10.2216/05-57.1The cell walls of red algae contain sulphated polysaccharides. It is believed that the bioactivity of such natural sulphated polysaccharides may be attributed to the sulphate groups. Knowledge of the mode of sulphation of these polysaccharides is, however, very limited. The current study forms part of our efforts to elucidate the mode of sulphation of the cell-wall polysaccharide of the red microalga Porphyridium sp. Although this microalga is an obligatory photoautotroph, under conditions of sulphate starvation it can assimilate the sulphur-containing amino acid cysteine (but not methionine) and incorporate sulphur from [35S]cysteine into the cell-wall polysaccharide. The ratio between 35S uptake to the soluble polysaccharide complex and to the cells was threefold higher from [35S]cysteine than that from Na235SO4, although the uptake of 35S to the cells was higher when Na235SO4 was used as the sulphur source. Pulse–chase experiments demonstrated that differences in the incorporation of 35S from the two sulphur sources were greater for the soluble polysaccharide complex (45.1% from [35S]cysteine vs. 13.9% from Na235SO4) than for the cellular fractions (bound polysaccharide, protein and low-molecular-weight fraction). SDS-PAGE analysis showed that the 35S label resided predominantly in the polysaccharide of the soluble complex and not in the glycoprotein. The effect of sodium chlorate, a sulphation inhibitor, on 35S incorporation into the soluble polysaccharide complex and the different cellular fractions depended on the 35S source: significant inhibition of sulphation of the soluble polysaccharide complex was found for [35S]cysteine as the source of sulphate, i.e. 87% vs.36.4% for Na235SO4. This study suggests that in addition to the commonly accepted sulphate pathway, there is another sulphation pathway in which cysteine serves as the sulphur source.

Superior Biolubricant from a Species of Red Microalga

The rheological properties of the sulfated polysaccharide of the red microalga Porphyridium sp., a heteropolymer with a molecular weight of 3-5 x 10(6) Da, indicated that this material might be an excellent candidate for lubrication applications: the viscosity of the polysaccharide is stable over a range of temperatures, pH values, and salinities. In this study, various rheological and lubricant properties of the polysaccharide were evaluated in comparison with those of a widely used biolubricant, hyaluronic acid. The viscosity of the Porphyridium sp. polysaccharide remained essentially unchanged in a temperature range of 25-70 degrees C. In tribology tests on a ball-on-flat ceramic pair, the values for the friction coefficient and wear rate for the pair lubricated with polysaccharide were remarkably lower than those for hyaluronic acid, especially at high loads. In a test on a steel ring/ultrahigh-molecular-weight polyethylene (UHMWPE) block pair, the wear tracks on the surface of the UHMWPE were more pronounced for hyaluronic acid than for the polysaccharide. Atomic force microscopy showed that the polysaccharide was effectively adsorbed onto mica surfaces, forming ultrathin coating layers in the nanometer range. As is required for biolubricant applications, the polysaccharide was not degraded by hyaluronidase. The stability of the Porphyridium sp. polysaccharide to heat and to hyaluronidase combined with its ability to reduce friction and wear indicate its potential as an advantageous biolubricant.

Antioxidant activity of the polysaccharide of the red microalga Porphyridium sp

The cells of the red microalga Porphyridium UTEX 637 are encapsulated within a sulfated polysaccharide whose external part (i.e., the soluble fraction) dissolves into the medium. It is thought that the main function of the polysaccharide is to protect the algal cells from the extreme environmental conditions, such as drought and high light, prevailing in their native sea-sand habitat. In this study, we evaluated the antioxidant properties of the water-soluble polysaccharide of Porphyridium sp. by determining the ability of a polysaccharide solution to inhibit: (1) autooxidation of linoleic acid, as determined by the standard thiobarbituric acid (TBA) and ferrous oxidation (FOX) assays; and (2) oxidative damage to 3T3 cells as determined by the dichlorofluorescein (DCFH) assay. In all three assays, the polysaccharide inhibited oxidative damage in a dose-dependent manner. Antioxidant activity was also exhibited by fractions of the polysaccharide obtained by sonication followed by separation on a reverse-phase HPLC with a C8 semi-preparative column. It is suggested that the antioxidant activity of the sulfated polysaccharide protects the alga against reactive oxygen species produced under high solar irradiation, possibly by scavenging the free radicals produced in the cell under stress conditions and transporting them from the cell to the medium.

Preparative purification of B-phycoerythrin from the microalga Porphyridium cruentum by expanded-bed adsorption chromatography

B-Phycoerythrin (B-PE) is a major light-harvesting pigment of microalgae. Due to its high fluorescence efficiency and its intense and unique pink color, it is widely used as a fluorescent probe and analytical reagent as well as being employed as a natural dye in foods and cosmetics. Tedious methodologies for B-PE purification have been published. In this work we present a new, fast, preparative and scaleable two-step chromatographic method for B-PE purification from the red microalga Porphyridium cruentum. Initially, phycobiliproteins were released from the microalga cells by osmotic shock and captured by applying the centrifuged cell suspension to a column containing 74 ml Streamline-DEAE equilibrated with 50 m M acetic acid–sodium acetate buffer, pH 5.5, using expanded-bed adsorption chromatography at an upward flow of 200 cm h −1. After adsorption, washing was carried out in the expanded-bed mode. Having removed unbound proteins and cellular debris, the bed was allowed to sediment and a B-PE-rich solution was eluted with a downward flow of the same 250 m M buffer. In order to obtain pure B-PE, we utilized conventional ion-exchange chromatography with a column of DEAE-cellulose loaded directly with the eluate from Streamline-DEAE and developed using a discontinuous gradient of acetic acid–sodium acetate buffer, pH 5.5. With this new methodology, 66% of B-PE contained in the biomass of the microalgae was recovered, a value significantly higher than those obtained following other methodologies. The B-PE purity was tested using sodium dodecyl sulfate–polyacrylamide gel electrophoresis and spectroscopic characterization.

FLORIDOSIDE AS A CARBON PRECURSOR FOR THE SYNTHESIS OF CELL‐WALL POLYSACCHARIDE IN THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA)1

Although red algae are known to be obligatory photoautotrophs, the red microalga Porphyridium sp. was shown to assimilate and metabolize floridoside. A pulse‐chase experiment with [14C]floridoside showed that at the end of a 240‐min pulse, 70% of total 14C‐uptake by the cells remained in the floridoside fraction. To evaluate the assimilation of floridoside by Porphyridium sp. cells, we exposed Porphyridium sp. not only to [14C]floridoside but also to its constituents, [14C]glycerol and [14C]galactose, as compared with [14C]bicarbonate. The extent of incorporation of [14C] galactose by the Porphyridium sp. cells was insignificant (50–80 dpm·mL−1), whereas uptake of 14C from [14C]glycerol into the algal cells was evident (2.4 × 103 dpm·mL−1) after 60 min of the pulse. The pattern of 14C distribution among the major constituent sugars, xylose, glucose and galactose, of the labeled soluble polysaccharide was dependent on the 14C source. The relative content of [14C]galactose in the soluble polysaccharide was highest (28.8%) for [14C]floridoside‐labeled culture and lowest (19.8%) for the [14C]glycerol‐labeled culture. Upon incubation of [14C]floridoside with a crude extract of a cell‐free system prepared from nonlabeled cells of Porphyridium sp., the label was indeed found to be incorporated into the sulfated polysaccharide. Our results suggested that the carbon metabolic pathway in Porphyridium sp. passes through the low molecular weight photoassimilatory product—floridoside—toward sulfated cell‐wall polysaccharide production.