Many Species Of Microalgae Research Articles

Structural properties of the extracellular biopolymer (β-D-xylo-α-D-mannan) produced by the green microalga Gloeocystis vesiculosa Nägeli

Many species of microalgae produce a relatively diverse range of metabolites that are interesting for biotechnological applications, and among them exopolysaccharides attract attention due to their structural complexity, biological activities, biodegradability or biocompatibility. An exopolysaccharide of high molecular weight (Mp) of 6.8 × 105 g/mol was obtained by cultivation of the freshwater green coccal microalga Gloeocystis vesiculosa Nägeli 1849 (Chlorophyta). Chemical analyses revealed a dominance of Manp (63.4 wt%), Xylp and its 3-O-Me-derivative (22.4 wt%), and Glcp (11.5 wt%) residues. The results of the chemical and NMR analyses showed an alternating branched 1,2- and 1,3-linked α-D-Manp backbone terminated by a single β-D-Xylp and its 3-O-methyl derivative at O2 of the 1,3-linked α-D-Manp residues. The α-D-Glcp residues were found mainly as 1,4-linked and to a lesser extent as the terminal sugar, indicating partial contamination of β-D-xylo-α-D-mannan with amylose (∼10 wt%) in G. vesiculosa exopolysaccharide.

Selection and Cultivation of Microalgae for CO2 Biofixation

Climate change has become the main focus of the world which caused various negative impacts throughout the earth. Carbon dioxide is one of the greenhouse gases that effect on climate change and environmental pollution. One of the promising opportunities to reduce CO2 emissions in the atmosphere is bio fixation by microalgae. Many species of microalgae have the ability to capture carbon dioxide as its carbon source for the photosynthetic process. This research aimed to cultivate many species of microalgae in the carbon dioxide incubator and study its CO2 bio-fixation capability. Microscopic analysis was occurred to identify microalgae morphology. The optical density measured representing growth rate of microalgae. Tetraselmis sp. and Navicula sp. are suitable for CO2 biofixaton due to the good adaptation to the existence of CO2 in the medium.

High Resolution Proteome of Lipid Droplets Isolated from the Pennate Diatom Phaeodactylum tricornutum (Bacillariophyceae) Strain pt4 provides mechanistic insights into complex intracellular coordination during nitrogen deprivation.

Lipid droplets (LDs) are an organelle conserved amongst all eukaryotes, consisting of a neutral lipid core surrounded by a polar lipid monolayer. Many species of microalgae accumulate LDs in response to stress conditions, such as nitrogen starvation. Here, we report the isolation and proteomic profiling of LD proteins from the model oleaginous pennate diatom Phaeodactylum tricornutum, strain Pt4 (UTEX 646). We also provide a quantitative description of LD morphological ontogeny, and fatty acid content. Novel cell disruption and LD isolation methods, combined with suspension-trapping and nanoflow liquid chromatography coupled to high resolution mass spectrometry, yielded an unprecedented number of LD proteins. Predictive annotation of the LD proteome suggests a broad assemblage of proteins with diverse functions, including lipid metabolism and vesicle trafficking, as well as ribosomal and proteasomal machinery. These proteins provide mechanistic insights into LD processes, and evidence for interactions between LDs and other organelles. We identify for the first time several key steps in diatom LD-associated triacylglycerol biosynthesis. Bioinformatic analyses of the LD proteome suggests multiple protein targeting mechanisms, including amphipathic helices, post-translational modifications, and translocation machinery. This work corroborates recent findings from other strains of P. tricornutum, other diatoms, and other eukaryotic organisms, suggesting that the fundamental proteins orchestrating LDs are conserved, and represent an ancient component of the eukaryotic endomembrane system. We postulate a comprehensive model of nitrogen starvation-induced diatom LDs on a molecular scale, and provide a wealth of candidates for metabolic engineering, with the potential to eventually customize LD contents.

CaCO3 supplementation of low-carbon wastewaters for the cultivation of Microalgae : a study with Desmodesmus multivariabilis

Microalgal biomass cultivated in wastewater has the potential for refining to energy products such as biodiesel and biohydrogen with the additional benefit of also treating the wastewater. As many species of microalgae can employ both Heterotrophic and Autotrophic modes of carbon synthesis, low-carbon waters benefit from the addition of inorganic carbon to the water. Capital and operational costs are a deterrent to using CO2 and other alternatives may be more attractive. NaHCO3 is a popular alternative but as a result of its solubility and alkalinity quickly raises the pH of the water which inhibits algal growth due the presence of free ammonia at high pH values. In this experiment, the growth of a South African strain of Desmodesmus multivariabilis was studied in the presence of solid calcium carbonate. Calcium carbonate was chosen for its low solubility, which would potentially allow for its dissolution to be driven by the inorganic carbon uptake in the media. The performance was compared to that of aerated wastewater and wastewater with solid CaSO4 as a non-carbon-containing substitute. It was found that there were significant differences in the growth and metabolism of all three experiments. Growth in the presence of solid calcium carbonate and calcium sulphate showed a preference for attached growth in the vicinity of solids, while suspended growth was preferred when just air was supplied. Furthermore, the experiment with air showed the highest growth rate, nitrogen uptake and a biomass yield that was more than an order of magnitude higher than with CaCO3. The experiment with CaSO4 showed low yields and growth rates, possibility indicating and inhibitory effect of the CaSO4. In the presence of CaCO3, a very high yield of extracellular organic metabolites was observed. The presence of these metabolites, as well as the stability of the pH and low growth, is a possible indication that the organism was controlling the pH as a defence mechanism. Despite not being a favourable substrate for growing D. multivariabilis, the high yield of extracellular metabolites may have a commercial potential, and the nature and use these metabolites deserve further investigation.

Toxic effect and bioaccumulation of selenium in green alga Chlorella pyrenoidosa

Se is required for the growth and metabolism of many species of microalgae. However, high concentrations of Se show toxicity to microalgal cells. In the study, the biomass, growth rate, total Se content, organic Se content, SOD, CAT, and LPO of Chlorella pyrenoidosa in an environment containing Se were determined to explore the effects of selenite on the growth of C. pyrenoidosa in different growth phases (exponential phase, late exponential phase, and early stationary phase). Bioaccumulation and conversion of selenium in C. pyrenoidosa and toxic effect of selenium were further explored. A low dosage of selenite could promote the growth of C. pyrenoidosa, but the higher Se concentration strongly inhibited growth and led to the low biomass. Algae cells in exponential phase could be exposed to high doses of selenium (≤ 5 mg L−1), which was higher than that for the cells in late exponential phase (≤ 2 mg L−1) and the cells in early stationary phase (≤ 2 mg L−1). The optimal growth conditions for enriching selenium in C. pyrenoidosa in exponential phase were determined as 2 mg L−1 selenite and 5-day cultivation. The highest transformation mass was 78 ± 0.5% and corresponding intracellular accumulation of organic Se was 72 ± 0.1 μg g−1 dry weight. The lower Se concentration induced the activities of oxidases, which was conducive to the growth of microalgal cells. The higher concentration of Se significantly induced the activities of oxidases, indicating that Se accumulation had a significant toxic effect on C. pyrenoidosa. In this way, a great quantity of Se-enriched biomass can be produced for nutritional purposes.

RNA-Seq-mediated transcriptomic analysis of heat stress response in a polar Chlorella sp. (Trebouxiophyceae, Chlorophyta)

The current outlook on mitigation of global warming does not appear promising, with figures in the reduction of anthropogenic greenhouse gas emissions lagging far behind climate goals. A recent environmental report even postulated a high possibility of temperature increase of at least 3 °C by 2100. Despite the low number of human inhabitants in Antarctica, the Antarctic Peninsula was reported as one of the most rapidly warming locations on earth. Many studies have shown that heat stress modulates physiological performance in many species of microalgae; however, studies to elucidate the molecular mechanisms of high-temperature thermotolerance are generally focused on the model species, i.e. Chlamydomonas reinhardtii. Furthermore, previous transcriptomic work in this aspect generally employed the microarray technique and/or involved the tropical or temperate strains, and few were conducted on the polar strains. In this study, RNA-Seq-mediated transcriptomic analysis was undertaken to compare the whole transcriptome profile of an Antarctic Chlorella sp. grown at ambient (4 °C) versus stress-inducing high (33 °C) temperatures and harvested at the 120-h time point. The findings of this study indicated a coordinated response to fine tune balance between energy production and utilisation for biosynthesis by redirecting carbon provision, and the arrest of cell division as a coping mechanism for an intense and relatively long period of stress. The strategies undertaken by this alga in acclimation to heat stress are somewhat similar to the heat stress response of the model species.

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans

BackgroundDay/night cycles regulate the circadian clock of organisms to program daily activities. Many species of microalgae have a synchronized cell division when grown under a day/night cycle, and synchronization might influence biomass yield and composition. Therefore, the aim of this study was to study the influence of day/night cycle on biomass yield and composition of the green microalgae Neochloris oleoabundans. Hence, we compared continuous turbidostat cultures grown under continuous light with cultures grown under simulated day/night cycles.ResultsUnder day/night cycles, cultures were synchronized as cell division was scheduled in the night, whereas under continuous light cell division occurred randomly synchronized cultures were able to use the light 10–15% more efficiently than non-synchronized cultures. Our results indicate that the efficiency of light use varies over the cell cycle and that synchronized cell division provides a fitness benefit to microalgae. Biomass composition under day/night cycles was similar to continuous light, with the exception of starch content. The starch content was higher in cultures under continuous light, most likely because the cells never had to respire starch to cover for maintenance during dark periods. Day/night cycles were provided in a ‘block’ (continuous light intensity during the light period) and in a ‘sine’ (using a sine function to simulate light intensities from sunrise to sunset). There were no differences in biomass yield or composition between these two ways of providing light (in a ‘block’ or in a ‘sine’).ConclusionsThe biomass yield and composition of N. oleoabundans were influenced by day/night cycles. These results are important to better understand the relations between research done under continuous light conditions and with day/night cycle conditions. Our findings also imply that more research should be done under day/night cycles.

Production of BMAA and DAB by diatoms (Phaeodactylum tricornutum, Chaetoceros sp., Chaetoceros calcitrans and, Thalassiosira pseudonana) and bacteria isolated from a diatom culture

Microalgae have previously been reported to contain β-N-methylamino-l-alanine (BMAA), and the global presence of these primary producers has been associated with the widespread occurrence of BMAA in marine organisms. It has been repeatedly shown that filter-feeding bivalves accumulate phytoplankton species and their toxins. In this study, the concentrations of total soluble BMAA and DAB as a function of growth phase were observed for four non-axenic diatom species (i.e. Phaeodactylum tricornutum, Chaetoceros sp., Chaetoceros calcitrans and Thalassiosira pseudonana). These strains had previously been shown to contain BMAA using a highly selective HILIC-MS/MS method. BMAA cell quota appeared to be species-specific, however, highest BMAA concentrations were always obtained during the stationary growth phase, for all four species, suggesting that BMAA is a secondary metabolite. While DAB was detected in a bacterial culture isolated from a culture of P. tricornutum, the presence or absence of a bacterial population did not influence production of BMAA and DAB by P. tricornutum, i.e. no significant difference was noted for BMAA and DAB production between axenic and non-axenic cultures. The presence of DAB in bacteria had previously been shown, and raised the question as to whether DAB observed in many species of microalgae may arise from the non-axenic culture conditions or from the microalgae themselves.

Microalgae based biodiesel production – current and future scenario

Microalgae have a clear potential to be used as a source for the production of biofuel. In order to utilize microalgae for this purpose, the most common systems for cultivating and harvesting them are investigated in the previous years. Since there are many species of microalgae with varying lipid accumulating characteristics, a diversity of options for the production of microalgae based energy have been analyzed. Subsequently, the energy inputs and conditions needed for growing and harvesting the microalgae and its oil production potentials are examined. This concludes with a formulation of complete concept for producing a renewable energy carrier from microalgae, which will be used for in-depth analysis.Â

Astaxanthin-Producing Green Microalga Haematococcus pluvialis: From Single Cell to High Value Commercial Products.

Many species of microalgae have been used as source of nutrient rich food, feed, and health promoting compounds. Among the commercially important microalgae, Haematococcus pluvialis is the richest source of natural astaxanthin which is considered as “super anti-oxidant.” Natural astaxanthin produced by H. pluvialis has significantly greater antioxidant capacity than the synthetic one. Astaxanthin has important applications in the nutraceuticals, cosmetics, food, and aquaculture industries. It is now evident that, astaxanthin can significantly reduce free radicals and oxidative stress and help human body maintain a healthy state. With extraordinary potency and increase in demand, astaxanthin is one of the high-value microalgal products of the future.This comprehensive review summarizes the most important aspects of the biology, biochemical composition, biosynthesis, and astaxanthin accumulation in the cells of H. pluvialis and its wide range of applications for humans and animals. In this paper, important and recent developments ranging from cultivation, harvest and postharvest bio-processing technologies to metabolic control and genetic engineering are reviewed in detail, focusing on biomass and astaxanthin production from this biotechnologically important microalga. Simultaneously, critical bottlenecks and major challenges in commercial scale production; current and prospective global market of H. pluvialis derived astaxanthin are also presented in a critical manner. A new biorefinery concept for H. pluvialis has been also suggested to guide toward economically sustainable approach for microalgae cultivation and processing. This report could serve as a useful guide to present current status of knowledge in the field and highlight key areas for future development of H. pluvialis astaxanthin technology and its large scale commercial implementation.

Lipid profile remodeling in response to nitrogen deprivation in the microalgae Chlorella sp. (Trebouxiophyceae) and Nannochloropsis sp. (Eustigmatophyceae).

Many species of microalgae produce greatly enhanced amounts of triacylglycerides (TAGs), the key product for biodiesel production, in response to specific environmental stresses. Improvement of TAG production by microalgae through optimization of growth regimes is of great interest. This relies on understanding microalgal lipid metabolism in relation to stress response in particular the deprivation of nutrients that can induce enhanced TAG synthesis. In this study, a detailed investigation of changes in lipid composition in Chlorella sp. and Nannochloropsis sp. in response to nitrogen deprivation (N-deprivation) was performed to provide novel mechanistic insights into the lipidome during stress. As expected, an increase in TAGs and an overall decrease in polar lipids were observed. However, while most membrane lipid classes (phosphoglycerolipids and glycolipids) were found to decrease, the non-nitrogen containing phosphatidylglycerol levels increased considerably in both algae from initially low levels. Of particular significance, it was observed that the acyl composition of TAGs in Nannochloropsis sp. remain relatively constant, whereas Chlorella sp. showed greater variability following N-deprivation. In both algae the overall fatty acid profiles of the polar lipid classes were largely unaffected by N-deprivation, suggesting a specific FA profile for each compartment is maintained to enable continued function despite considerable reductions in the amount of these lipids. The changes observed in the overall fatty acid profile were due primarily to the decrease in proportion of polar lipids to TAGs. This study provides the most detailed lipidomic information on two different microalgae with utility in biodiesel production and nutraceutical industries and proposes the mechanisms for this rearrangement. This research also highlights the usefulness of the latest MS-based approaches for microalgae lipid research.

Azide improves triglyceride yield in microalgae

Many species of microalgae accumulate under growth-limiting conditions, such as nitrogen deprivation, large amounts of triglycerides (TAG). The regulation of this process is not clear. Here we demonstrate that sodium azide (Az) induces synthesis of high levels of TAG in the lipid-accumulating marine species Chlorella desiccata. In comparison to N deprivation, Az leads to only minor growth retardation and to smaller inhibition of photosynthesis and respiration, resulting in a 60–80% increase in TAG yield. Maximal TAG induction level by Az is strictly dependent on light intensity and requires high CO2. The cell morphology, TAG level and composition are similar in both treatments. From 17 tested microalgae species, 15 were responsive to Az under different culturing conditions. The results suggest that the higher TAG yield in Az-treated compared to N-deprived cultures, results from the better metabolic state and higher photosynthetic activity of the culture. The potential of Az to improve TAG yield production from microalgae is discussed.

Methods for sampling and analysis of marine microalgae in ship ballast tanks: a case study from Tampa Bay, Florida, USA

Ballasting and deballasting of shipping vessels in foreign ports have been reported worldwide as a vector of introduction of non-native aquatic plants and animals. Recently, attention has turned to ballast water as a factor in the global increase of harmful algal blooms (HABs). Many species of microalgae, including harmful dinoflagellate species, can re main viable for months in dormant benthic stages (cysts) in ballast sediments. Over a period of four years, we surveyed ballast water and sediment of ships docked in two ports of Tampa Bay, Florida, USA. Sampling conditions encountered while sampling ballast water and sediments were vastly different between vessels. Since no single sample collection protocol could be applied, existing methods for sampling ballast were modified and new methods created to reduce time and labor necessary for the collection of high-quality, qualitative samples. Five methods were refined or developed, including one that allowed for a directed intake of water and sediments. From 63 samples, 1,633 dinoflagellate cysts and cyst-like cells were recovered. A native, cyst-forming, harmful dinoflagellate, Alexandrium balechii (Steidinger) F. J. R. Taylor, was collected, isolated, and cultured from the same vessel six months apart, indicating that ships exchanging ballast water in Tampa Bay have the potential to transport HAB species to other ports with similar ecologies, exposing them to non-native, potentially toxic blooms.

Genetic engineering in marine cyanobacteria

Many species of microalgae producing useful materials have been isolated from marine environments. For their industrial application, widely applicable and stable gene expression is required. It is necessary to establish gene transfer methods as an essential first step in genetic manipulation. Although gene transfer techniques for cyanobacteria have been developed, only naturally transformable strains have been used. Here, we describe recent progress made in developing gene transfer methods for marine cyanobacteria. The following are covered: (1) transformation, (2) electroporation, (3) conjugation, (4) particle gun. A plasmid from the marine cyanobacterium, Synechococcus sp., whose copy number is dependent on salinity, was characterized. This plasmid is being used to develop a stable and controllable gene expression system.

Aquatic biomass and carbon dioxide trapping

The technology for growing microalgae as a renewable biomass source can be applied to the production of a diesel fuel substitute (biodiesel). Microalgae are of interest because of their high growth rates and tolerance to varying environmental conditions, and because the oils (lipids) they produce can be extracted and converted to substitute petroleum fuels. Projected global climate change provides a second important rationale for this approach. Climate change has been linked to the accumulation of excess carbon dioxide in the atmosphere. The burning of fossil fuels in power plants is the primary contributor to excess carbon dioxide. Inasmuch as the primary nutrient for microalgal growth is carbon dioxide, operation of microalgal biomass farms has emerged as a promising candidate in the search for alternative approaches to ameliorate global climate change. The production of diesel fuel by microalgae requires very large quantities of carbon dioxide as a nutrient. In areas where microalgae fuel farms operate in tandem with fossil fuel plants to scrub carbon dioxide from flue gases, the release of carbon dioxide could be significantly reduced. If the microalgae are used to produce fuel, a mass culture facility reduces by approximately 50% the carbon dioxide emissions from the power plant per million Btu delivered. For example, although coal is ordinarily considered to be the most polluting fossil fuel on the basis of carbon dioxide emitted per amount of energy produced, the incorporation of microalgal ponds with a coal-fired plant would make this fossil fuel less polluting than existing oil- and natural-gas-fired plants. Similar advantages can be achieved for oil- and gas-fired plants. If commodity chemicals are produced from algae instead of fuels, the net carbon dioxide reduction is significantly greater. Commodity chemicals can be used to produce goods with long-term uses such as building materials. Such uses would result in the sequestering of carbon dioxide for long periods. Of the photosynthetic organisms, microalgae are the most productive carbon dioxide users and can fix greater amounts of carbon dioxide per land area than higher plants. Also, maximum productivities of higher plants and trees are restricted to areas with prime soil, water, and climate (primarily the tropics). Plant leaves exist in an aerial environment and are subject to large evaporative moisture losses, which directly inhibit the process of photosynthesis (carbon dioxide uptake). Microalgae in mass culture are not subject to such photosynthetic inhibition because the water content of the culture can be controlled by proper engineering, and saline water can be used if necessary. This difference is the basis for the several-fold higher carbon dioxide absorption capacity of microalgae compared to plants. Initial application of this technology is envisioned for the Desert Southwest of the United States because this area provides high solar radiation and offers flat land that has few competing uses (hence low land costs). Also, there are large saline aquifers with few competing uses in the region. These could provide a suitable, low-cost culture medium for the growth of many species of microalgae.

The molecular and biochemical analyses of CO2‐concentrating mechanisms in cyanobacteria and microalgae

Abstract. The supply of dissolved inorganic carbon for photosynthesis in the aquatic environment is much more variable than that experienced by terrestrial plants. In response to this variability, cyanobacteria and many species of microalgae acclimate to rapid changes in the availability of dissolved inorganic carbon by the induction of high affinity/high capacity CO2‐concentrating systems (CCMs). Biochemical and molecular analyses of the acclimation response have recently identified several components that are required for efficient operation of the CCMs and CO2 assimilation. This has been accomplished using in vivo labelling studies, and characterization of high inorganic carbon (Ci) requiring cyanobacterial and algal mutants. The identification and regulation of expression of polypeptides synthesized in response to limiting Ci concentrations, and the proposed role of the carboxysome and the pyrenoid in the functioning of the CCMs are examined.