Microalga Porphyridium Purpureum Research Articles

An evaluation of the genotoxicity and 90-day repeated dose oral toxicity in rats of Porphyridium purpureum.

Interest in microalgae products for use in food is increasing, as demands for sustainable and cost-effective food choices grow due to the escalating global population and increase in climate-related struggles with agriculture. Toxicological assessments of some species of microalgae have been conducted, but there were little data available for the oral consumption of the red microalgae Porphyridium purpureum and no data on genotoxicity. This article articulates a genotoxicity assessment and a 90-day repeated dose oral toxicity study in rats performed according to OECD guidelines. Under the experimental conditions applied, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used in the bacterial reverse mutation test. Similarly, the test item did not induce structural chromosomal aberrations in V79 hamster lung cells. The test item also did not cause chromosomal damage in bone marrow of mice in the mammalian micronucleus test. The no observed adverse effect level (NOAEL) of the 90-day repeated dose oral toxicity study in rats was determined to be the highest dose tested, 3000 mg/kg bw/day. These data add to the body of evidence regarding the safety of P.purpureum for human consumption.

Effects of Silver Nanoparticles on the Red Microalga Porphyridium purpureum CNMN-AR-02, Cultivated on Two Nutrient Media.

The purpose of this study was to examine the influence of 10 and 20 nm nanoparticles (AgNPs) on the growth and biochemical composition of microalga Porphyridium purpureum CNMN-AR-02 in two media which differ by the total amount of mineral salts (MM1 with 33.02 g/L and MM2 with 21.65 g/L). Spectrophotometric methods were used to estimate the amount of biomass and its biochemical composition. This study provides evidence of both stimulatory and inhibitory effects of AgNPs on different parameters depending on the concentration, size, and composition of the nutrient medium. In relation to the mineral medium, AgNPs exhibited various effects on the content of proteins (an increase up to 20.5% in MM2 and a decrease up to 36.8% in MM1), carbohydrates (a decrease up to 35.8% in MM1 and 39.6% in MM2), phycobiliproteins (an increase up to 15.7% in MM2 and 56.8% in MM1), lipids (an increase up to 197% in MM1 and no changes found in MM2), antioxidant activity (a decrease in both media). The composition of the cultivation medium has been revealed as one of the factors influencing the involvement of nanoparticles in the biosynthetic activity of microalgae.

Optimized transgene expression in the red alga Porphyridium purpureum and efficient recombinant protein secretion into the culture medium

Microalgae represent a promising but yet underexplored production platform for biotechnology. The vast majority of studies on recombinant protein expression in algae have been conducted in a single species, the green alga Chlamydomonas reinhardtii. However, due to epigenetic silencing, transgene expression in Chlamydomonas is often inefficient. Here we have investigated parameters that govern efficient transgene expression in the red microalga Porphyridium purpureum. Porphyridium is unique in that the introduced transformation vectors are episomally maintained as autonomously replicating plasmids in the nucleus. We show that full codon optimization to the preferred codon usage in the Porphyridium genome confers superior transgene expression, not only at the level of protein accumulation, but also at the level of mRNA accumulation, indicating that high translation rates increase mRNA stability. Our optimized expression constructs resulted in YFP accumulation to unprecedented levels of up to 5% of the total soluble protein. We also designed expression cassettes that target foreign proteins to the secretory pathway and lead to efficient protein secretion into the culture medium, thus simplifying recombinant protein harvest and purification. Our study paves the way to the exploration of red microalgae as expression hosts in molecular farming for recombinant proteins and metabolites.

The Comparative Toxic Impact Assessment of Carbon Nanotubes, Fullerene, Graphene, and Graphene Oxide on Marine Microalgae Porphyridium purpureum.

The growing production and application of carbon-based nanomaterials (CNMs) represent possible risks for aquatic systems. However, the variety of CNMs with different physical and chemical properties and different morphology complicate the understanding of their potential toxicity. This paper aims to evaluate and compare the toxic impact of the four most common CNMs, namely multiwalled carbon nanotubes (CNTs), fullerene (C60), graphene (Gr), and graphene oxide (GrO) on the marine microalgae Porphyridium purpureum. The microalgae cells were exposed to the CNMs for 96 h and measured by flow cytometry. Based on the obtained results, we determined no observed effect level (NOEL), and calculated EC10 and EC50 concentrations for growth rate inhibition, esterase activity, membrane potential, and reactive oxygen species (ROS) generation changes for each tested CNM. According to the sensitivity (growth rate inhibition) of P. purpureum, the used CNMs can be listed in the following order (EC50 in mg/L, 96 h): CNTs (2.08) > GrO (23.37) > Gr (94.88) > C60 (>131.0). The toxicity of CNTs was significantly higher than the toxic effect of the other used CNMs, and only this sample caused an increase in ROS generation in microalgae cells. This effect was apparently caused by the high affinity between particles and microalgae associated with the presence of exopolysaccharide coverage on P. purpureum cells.

The Impact of Metal-Based Nanoparticles Produced by Different Types of Underwater Welding on Marine Microalgae.

Underwater wet welding is commonly used in joining pipelines and in underwater construction. Harmful and hazardous compounds are added to many flux-cored wires for underwater welding and cutting, and can have a negative impact on marine life. The specific objective of this study was to evaluate the aquatic toxicity of two suspension samples obtained using welding electrode and flux-cored wire in marine microalgae Attheya ussuriensis and Porphyridium purpureum. Growth rate inhibition, cell size, and biochemical changes in microalgae were evaluated by flow cytometry. The results of the bioassay demonstrated that the suspension obtained after welding with electrode had an acute toxic impact on diatomic microalgae A. ussuriensis, and both tested suspensions revealed chronic toxicity in this microalga with a 40% growth rate inhibition after exposure to 40-50% of prepared suspensions for 7 days. Red algae P. purpureum revealed tolerance to both suspensions caused by exopolysaccharide covering, which prevents the toxic impact of metal cations such as Al, Ti, Mn, Fe, and Zn, which are considered the main toxic components of underwater welding emissions.

Growth and B-Phycoerythrin Production of Red Microalga Porphyridium purpureum (Porphyridiales, Rhodophyta) under Different Carbon Supply.

Red microalga Porphyridium purpureum (Bory) Drew is a well-known object of biotechnology due to its unique ability to synthesize a wide range of biologically active compounds. Enough minerals in an accessible form in a medium are a prerequisite for maintaining a high growth rate of P. purpureum. Carbon is the main element of microalgal biomass and is a component of all organic compounds. The work aimed to study the morphological features of cells and the accumulation and production of B-phycoerythrin and total protein in P. purpureum biomass in different ways of supplying CO2 into the culture. In Variant 1, CO2 was directly injected into a gas-air mixture (2-3 percent v/v) used for culture bubbling via capillary. In Variant 2, the air was supplied to the culture through the aquarium sparger. Variant 3 was like the first one but without the additional introduction of carbon dioxide. The application of the method for sparging atmospheric air led to a significant increase in both the productivity of the P. purpureum and the rate of protein and B-phycoerythrin synthesis in comparison with growing it using the air without spraying (two-and-a-half times, five times, and more than eight times, respectively). Moreover, there were significant changes in the morphological structure of P. purpureum cells, which were visualized both by microscopy and by changes in the color of the culture. Based on the experimental data obtained, the variants for the carbon supply experiment were ranked as follows: Variant 1 is better than Variant 2 and Variant 3. The use of atomization as a technological method made it possible to speed up the transfer of carbon dioxide from the air to the medium, which helped to keep the growth rate of P. purpureum biomass and B-phycoerythrin accumulation high.

Therapeutic Potential of Microalgae-Derived Bioactive Metabolites Is Influenced by Different Large-Scale Culture Strategies.

Microalgae have been identified as one of the most promising sources of novel bioactive compounds for biomedical applications, the food industry, and cosmetics. In the last decade, several biotechnological developments have facilitated the identification of a growing number of compounds as well as the study of optimal microalgae culture conditions for the production of biomass enriched in specific molecules of interest. In this study, two common commercial marine microalgae (Nannochloropsis oculata and Porphyridium purpureum) were cultured in standard and nutrient-stressed conditions and the obtained biomass extracts were assessed for their potential to inhibit cancer cell proliferation and migration as well as their antioxidant activity. Results from viability in 2D and 3D cancer cell models showed an enhancement of the antitumour activity of P. purpureum in the 3D model compared to 2D, together with a greater capacity to reduce the migration capacity of cancer cells with the biomass from nutrient-stressed conditions, whereas the antioxidant activity of N. oculata decreased when exposed to nutrient-stressed conditions. To date, this is one of the few studies that proves that controlled changes in large-scale culturing conditions such as nutrient depletion have a relevant impact in the bioactivity of the biomass on cancer cells.

Freeze-thaw-assisted aqueous two-phase system as a green and low-cost option for analytical grade B-phycoerythrin production from unicellular microalgae Porphyridium purpureum

Microalgae are promising alternative sources for natural phycobiliprotein production since they grow rapidly and can be cultured on a large scale. However, the overall economic viability of analytical grade phycoerythrin production from microalgae is limited by the high cost of the pretreatment required to break down the cell wall, as well as the expensive reagents and equipment used during purification. This study developed a novel extraction and purification process to recovery B-phycoerythrin (B-PE) in a freeze-thaw-assisted aqueous two-phase system (FT-ATPS) from Porphyridium purpureum. The effects of culture strategy, extraction method and purification factors on B-PE production were studied systematically. The results revealed that low light induced B-PE synthesis, whereas hindered the growth. The stepwise light supplement strategy alleviated the growth limitation under low-light conditions and increased the final B-PE production, up to 182.1 ± 4.1 mg/L (increasing by 73.1 %). Compared with the traditional electricity highly-consumed ultrasonication method, the green freeze-thaw method could extract B-PE without damaging the cell structure and save much more power (>98 %), and the extraction rate reached the highest when frozen at −80 °C. The purity and concentration of B-PE in crude extract were proved to have a significant effect on ATPS purification, and the higher the former, the better the latter. A total production cost of 0.045 $/mg (decreasing by 96.2 %) and purity of 5.6 ± 0.2 (A545/A280) for analytical grade B-PE production were achieved by FT-ATPS based on 4 % polyethylene glycol (PEG2,000) and 20 % ammonium sulfate. Relative to the conventional method of phycoerythrin production, the method developed herein has greater safety, lower cost, and more environmental benefits, which can be function appropriately in the expensive purification of analytical grade phycobiliproteins.

Synthesis and evaluation of cationic polyacrylamide and polyacrylate flocculants for harvesting freshwater and marine microalgae

• Cationic PAETAC & PAmPTAC were synthesized by UV-induced radical polymerization. • New polymers showed good flocculation performance of freshwater & marine microalgae. • Optimal doses of PAETAC were 50 and 4.8 mg/g for C. vulgaris & P. purpureum. • PAETAC and PAmPTAC produced stable flocs, supporting simple dewatering step. This study addresses the challenge of microalgae harvesting through the development of flocculants. Two positively charged cationic polymers including poly[2 (acryloyloxy)ethyl]trimethylammonium chloride (PAETAC) and poly(3 acrylamidopropyl)trimethylammonium chloride (PAmPTAC) were synthesized using the UV-induced radical polymerization, for harvesting both freshwater and marine microalgae. The results show that the synthesized polymers have excellent flocculation performance for both freshwater green microalgae ( Chlorella vulgaris) and marine red microalgae ( Porphyridium purpureum). PAETAC outperformed PAmPTAC for both Chlorella vulgaris and Porphyridium purpureum microalgae. The optimal PAETAC doses for Chlorella vulgaris and Porphyridium purpureum microalgae were 50 and 4.8 mg/g of dry biomass while the optimal PAmPTAC doses were 252 and 35 mg/g of dry biomass respectively. Additionally, the floc formation with the PAETAC was more stable than PAmPTAC, which supported the dewatering step via sieving. The superior performance can be attributed to the higher molecular weight of the PAETAC polymer when compared to the PAmPTAC polymer. In comparison to commercially available polydiallyldimethylammonium chloride (PolyDADMAC), the newly synthesised PAETAC and PAmPTAC polymers demonstrated superior flocculation efficiency at a lower dose. The findings of this study established a platform technology for designing and synthesising cationic flocculants for use in microalgae harvesting.

Production characteristics of Porphyridium purpureum (Bory) Drew et Ross semi-continuous culture at low irradiance

The red microalga Porphyridium purpureum (Bory de Saint-Vincent, 1797) Drew et Ross, 1965 is of great interest to researchers as a source of various biologically valuable substances, with their content in cells being determined by cultivation conditions. Phycobiliproteins concentration in P. purpureum cells depends directly on nitrogen concentration in the culture medium and cell irradiance. Semi-continuous cultivation allows maintaining these parameters at a level given. The aim of the work was to study P. purpureum culture growth and B-phycoerythrin (B-PE) accumulation and production at low irradiance, with minimal rates of pigment photodestruction. P. purpureum semi-continuous (quasi-continuous) cultivation was carried out at a specific flow rate of 0.1 and 0.2 day−1 and mean surface irradiance of 5 and 25 W·m−2. P. purpureum culture productivity increased by 1.6–17 times both with a rise in surface irradiance 5 to 25 W·m−2 and an increase in the medium specific flow rate 0.1 to 0.2 day−1. Maximum productivity values for the experimental conditions (0.21 g·L−1·day−1) were recorded at 25 W·m−2 and 20 % medium specific flow rate, but those were 1.5–2 times lower than the precalculated ones. In P. purpureum cells, protein and B-PE concentrations decreased both with an increase in surface irradiance (by 15–20 %) and with a rise in a specific flow rate (by 1.5 times) for all the variants. The shifts in protein and B-PE concentration in P. purpureum culture had a unidirectional character as well; those mainly corresponded to the shift in the culture density. P. purpureum B-PE productivity increased by 1.5–1.9 times with a rise in surface irradiance 5 to 25 W·m−2. Maximum B-PE productivity (13 mg·L−1·day−1) was recorded for the variants of the experiment with a surface irradiance of 25 W·m−2 (0.1 and 0.2 day−1). An increase in specific irradiance of P. purpureum cells 7 to 26 W·g−1 resulted in a rise in biomass productivity by 2.6 times; in B-PE productivity, by 1.8 times; and in protein productivity, by 1.7 times. In the experiment, irradiance was the factor determining the production characteristics of P. purpureum culture, and it was confirmed by the data obtained.

Separation of the absorption spectrum of Porphyridium purpureum (Bory) Ross. in the red area

Mathematical decomposition of the absorption spectrum of the culture of the red microalga Porphyridium purpureum (Bory) Ross was carried out in the spectral range from 550 to 750 nm. The culture spectra were recorded on a spectrophotometer with an integrating sphere. Using the literature data, mathematical models of the absorption spectra of the following pigments were compiled: B-phycoerythrin, R-phycocyanin, allophycocyanin and chlorophyll a. The mathematical model of each pigment represented the sum of Gaussian curves. The resulting equations were taken as a basis for modeling the native spectrum. A general model of the absorption spectrum of culture in the region of 550–750 nm has been compiled, consisting of the sum of individual pigments. Using the model obtained in practice, it is possible to determine the concentrations of chlorophyll a, and individual phycobilin pigments directly from the absorption spectrum of the culture.

Assessment of light distribution model for marine red microalga Porphyridium purpureum for sustainable production in photobioreactor

Microalgae can accumulate large amounts of nutrients from sustainable elements cycling and wastewater reuse. Light is a key factor determining productivity of algal biomass when recycling. However, light is unevenly distributed in photobioreactors due to light absorption and scatter by algal cells. Understanding the laws of light distribution is needed for optimizing the culture process. In this study, a light distribution model for red alga Porphyridium purpureum was used to optimize the cultivation process and improve culture performance by controlling light intensity. Compared to the Lambert-Beer model, the Hyperbolic law is more flexible and is applicable in a larger range of cell densities. In addition, the content of intracellular phycobiliprotein has a great influence on light distribution inside the photobioreactor while a higher biomass concentration reduces its impact. A maximum biomass concentration of 24.7 g/L along with 1.2 g/L/d cell growth rate was achieved by increasing incident light intensity in a stepwise fashion. The overall light conditions inside the photobioreactor during the culture process was also analyzed and discussed based on light distribution models. A volume-averaged light intensity regulated at ~50 μmol/m2/s along with an incident light intensity of less than 540 μmol/m2/s is an appropriate light condition for Porphyridium purpureum culture. The outcomes of light distribution model assessment and stepwise fashion regulation strategy can be applied to red microalgae in general, especially for high cell density cultivation. These findings provide an essential base for culture optimization, which can be used in future industrial applications of P. purpureum for water clean and sustainability of human nourishment production.

Porphyridium purpureum microalga physiological and ultrastructural changes under copper intoxication.

The present work assessed the effect of copper (Cu) on cell dynamics and structure of the microalga Porphyridium purpureum (Rhodophyta, Bangiophycidae). Ultrastructure of the microalga was investigated and fluorescence of chlorophyll a and phycoerythrin, and content of reactive oxygen species (ROS) were estimated by flow cytometry. The number of cells did not show statistically significant differences at concentrations of 50 and 100 μg/L of Cu compared to the control, whereas 150 μg/L of Cu inhibited population growth. The fluorescence of chlorophyll a increased following exposure to Cu 100 μg/L and fluorescence of phycoerythrin enhanced by Cu 150 μg/L. There was no alteration in the above indicators at other concentrations. The content of ROS increased with increasing Cu concentration in a dose-dependent manner. The population size structure was also changed by Cu as the number of cells sized 4-6 μm was increased in the presence of Cu, especially with Cu 150 μg/L. Changes in the topography of thylakoids grew larger with Cu concentration.

Growth of Porphyridium purpureum (Porphyridiales, Rhodophyta) and Production of B-Phycoerythrin under Varying Illumination

The red pigment B-phycoerythrin (B-PE) belongs to the group of phycobiliproteins (PBPs). It is a part of the light-harvesting pigment complex of the red microalga Porphyridium purpureum (Bory) Drew et Ross, and its amount in cells is determined by the level of irradiation and nitrogen supply. B-PE is a valuable natural pigment whose biotechnological potential is used in nutraceuticals, pharmaceuticals, food and cosmetic industries, and in biomedical research and clinical diagnostics. The dynamics of cell number and the content of photosynthetic pigments are quite often assessed in experiments with P. purpureum. The culture’s density is low in the majority of the experiments, although it is known that it can reach 10 g/L of dry matter. The aim of the study was to investigate the features of the accumulation and production of PBPs in a dense culture of P. purpureum under varying illumination. The molecular-genetic analysis confirmed the taxonomic affiliation of P. purpureum culture. Algae were grown in flat plate photobioreactors with an average illumination of 5, 10, and 15 klx. The dynamics of culture density, the content of B-PE, and production characteristics were used as indicators. It was shown that an increase in the microalgae culture density corresponding to the calculated nitrogen concentration in the nutrient medium was obtained only under illumination of 5 klx. Illumination increased to 10, and 15 klx caused a decrease in both the maximum and average productivities of the culture by 2.5–3.5 times. It was experimentally shown that the highest content of B-PE in the cells and culture of P. purpureum (5.5% of dry matter and 74 mg/L, respectively) was observed under illumination of 5 klx. The pattern of the change in B-PE content in P. purpureum culture was determined depending on the specific illumination of microalgae cells: the pigment concentration hyperbolically decreased with increasing specific illumination. Thus, the level of illumination of P. purpureum microalgae cells had a significant effect on the growth characteristics of the culture (growth rate, B-PE synthesis rate and yield): a lower level of surface illumination was preferred for P. purpureum cultivation. The approach proposed in the study allows one to reduce material costs during the cultivation of P. purpureum while maintaining a high growth rate of the culture.

Surface plasma treatment (Ar/CF4) decreases biofouling on polycarbonate surfaces

The purpose of this study was to examine the impact of hydrophobicity, surface chemistry and topography on bacterial and microalgal adhesion. To this end, the effects of surface plasma treatments (argon (Ar) and tetrafluorocarbon (CF4)) of polycarbonate substrates on bioadhesion were investigated in vitro. Surfaces were characterized by goniometry, atomic force microscopy and X-ray photoelectron spectroscopy. Two marine bacterial strains, a hydrophobic Pseudoalteromonas sp. 5M6 and a hydrophilic Paracoccus sp. 4M6, and two microalgae (Cylindrotheca closterium and Porphyridium purpureum) involved in marine biofouling were selected. Their adhesion onto the substrates was observed and quantified using confocal laser scanning microscopy–microfluidic flow cells. It was demonstrated that the combination of three parameters – namely, surface energy, fluorination and nanotopography – significantly decreases the adhesion of three microorganisms out of four (Pseudoalteromonas sp. 5M6, C. closterium and P. purpureum), whereas one parameter on its own is insufficient.

Efficient accumulation of high-value bioactive substances by carbon to nitrogen ratio regulation in marine microalgae Porphyridium purpureum

An efficient biomass and high-value bioactive substances production strategy was developed for unicellular microalgae Porphyridium purpureum. We studied the optimal culture method and metabolites accumulation under different C/N conditions, and further proposed methods to increase the yield under high C/N ratio. The highest biomass reached 16.24 g/L with ASW medium by mixotrophy. High C/N ratio and mediate C/N can significantly promote the synthesis and secretion of polysaccharides, as well as the accumulation of ω-6 PUFAs; however, inhibit the growth, resulting in lower yield. With the significant increase of C/N ratio, protein degradation was accelerated, providing sufficient nitrogen source for efficient accumulation of carbohydrates (1.66 g/L EPS) and PUFAs (231.24 mg/L ARA). Finally, we reduced the growth inhibition, shortened the culture cycle, and doubled the final biomass to 9.34 g/L under nitrogen deficiency condition. Our exploitation of a cost-effective and feasible culture method for red algae is particularly significant.

Влияние меди на численность, морфологию клеток и содержание фотосинтетических пигментов микроводоросли Porphyridium purpureum

Изучили возможности адаптации красной водоросли Porphyridium purpureum к интоксикации медью. В качестве показателей использовали динамику численности клеток, морфологию клеток, содержание хлорофилла a и каротиноидов. Эксперимент проводили в два этапа. На первом исследовали действие меди в концентрациях 50 и 100 мкг·л−1; на втором оценивали адаптивные способности водоросли к росту в загрязнённой Cu2+ среде. Установлено, что на первом этапе присутствие меди в среде в концентрации 50 мкг·л−1 существенно не сказывалось на исследуемых показателях. Внесение 100 мкг·л−1 вызывало угнетение роста и снижение содержания фотосинтетических пигментов. Показано, что на втором этапе после пересева из среды, содержащей 50 мкг·л−1, в среду с такой же концентрацией количество клеток и содержание фотосинтетических пигментов достоверно не отличались от контрольных. Часть клеток деформировалась, хлоропласты были тёмными. При пересеве из среды, содержащей 50 мкг·л−1, в среду со 100 мкг·л−1 зафиксировано отставание в росте в два раза; в суспензии обнаружено большое количество клеток с тёмным зернистым хлоропластом. Перенос клеток из среды со 100 мкг·л−1 в среду с такой же концентрацией вызывал подавление роста и уменьшение содержания фотосинтетических пигментов. В суспензии обнаружены клетки с диаметром, превышающим контрольный; отмечено большое количество слизи. Установлено, что полноценной адаптации P. purpureum к содержанию меди в среде не происходило.

Toxicity assessment of particulate matter emitted from different types of vehicles on marine microalgae

Air pollution caused by vehicle emissions remains a serious environmental threat in urban areas. Sedimentation of atmospheric aerosols, surface wash, drainage water, and urbane wastewater can bring vehicle particle emissions into the aquatic environment. However, the level of toxicity and mode of toxic action for this kind of particles are not fully understood. Here we explored the aquatic toxic effects of particulate matter emitted from different types of vehicles on marine microalgae Porphyridium purpureum and Heterosigma akashiwo.We used flow cytometry to evaluate growth rate inhibition, changes in the level of esterase activity, changes in membrane potential and size changes of microalgae cells under the influence of particulate matter emitted by motorcycles, cars and specialized vehicles with different types of engines and powered by different types of fuel.Both microalgae species were highly influenced by the particles emitted by diesel-powered vehicles. These particle samples had the highest impact on survival, esterase activity, and membrane potential of microalgae and caused the most significant increase in microalgae cell size compared to the particles produced by gasoline-powered vehicles. The results of the algae-bioassay strongly correlate with the data of laser granulometry analyses, which indicate that the most toxic samples had a significantly higher percentage of particles in the size range less than 1 μm. Visual observation with an optical microscope showed intensive agglomeration of the particles emitted by diesel-powered vehicles with microalgae cells. Moreover, within the scope of this research, we did not observe the direct influence of metal content in the particles to the level of their aquatic toxicity, and we can conclude that physical damage is the most probable mechanism of toxicity for vehicle emitted particles.

Using a trait-based approach to optimize mixotrophic growth of the red microalga Porphyridium purpureum towards fatty acid production

BackgroundOrganic carbon sources have been reported to simultaneously increase the growth and lipid accumulation in microalgae. However, there have been no studies of the mixotrophic growth of Porphyridium purpureum in organic carbon media. In this study, three organic carbon sources, glucose, sodium acetate, and glycerol were used as substrates for the mixotrophic growth of P. purpureum. Moreover, a novel trait-based approach combined with Generalized Additive Modeling was conducted to determine the dosage of each organic carbon source that optimized the concentration of cell biomass or fatty acid.ResultsA 0.50% (w/v) dosage of glucose was optimum for the enhancement of the cell growth of P. purpureum, whereas sodium acetate performed well in enhancing cell growth, arachidonic acid (ARA) and eicosapentaenoic acid (EPA) content, and glycerol was characterized by its best performance in promoting both cell growth and ARA/EPA ratio. The optimum dosages of sodium acetate and glycerol for the ARA concentration were 0.25% (w/v) and 0.38% (v/v), respectively. An ARA concentration of 211.47 mg L−1 was obtained at the optimum dosage of glycerol, which is the highest ever reported.ConclusionsThe results suggested that a comprehensive consider of several traits offers an effective strategy to select an optimum dosage for economic and safe microalgae cultivation. This study represents the first attempt of mixotrophic growth of P. purpureum and proved that both biomass and ARA accumulation could be enhanced under supplements of organic carbon sources, which brightens the commercial cultivation of microalgae for ARA production.

Protein extraction and bioactive hydrolysate generation from two microalgae, Porphyridium purpureum and Phaeodactylum tricornutum

Microalgae are a relatively underutilised source of valuable nutritional compounds and biochemicals. Their high protein contents make them an interesting target for the generation of bioactive peptides for the functional food industry. Here, the nitrogenous components of the red microalga Porphyridium purpureum and the diatom- Phaeodactylum tricornutum were quantified, and their SDS-PAGE profiles analysed. Proteinswere isolated from these species by solubilisation at alkaline pH followed by precipitation at acidic pH. The protein extracts were hydrolysed with the food-grade proteolytic preparations Alcalase 2.4 L and Flavourzyme 500 L. The P. purpureum and P. tricornutum hydrolysates were examined for their in vitroanti-diabetic and antioxidant properties. The microalgal-derived protein hydrolysates had dipeptidyl peptidase (DPP) IV inhibitory activity, with IC50 values of 2.28 ± 0.36 and 2.68 ± 0.19 mg/mL for P. purpureum and P. tricornutum, respectively. The oxygen radical absorbance capacity (ORAC) and ferric reducing power (FRAP) values were, respectively, 13.98 ± 0.97 and 478.94 ± 34.43 for P. purpureum, and 15.04 ± 0.54 and 155.74 ± 38.30 for P. tricornutum expressed in μmol Trolox Equivalent (TE) per gram of dry matter.The results suggest that protein hydrolysates from these microalgae have potential use as functional food ingredients.