Confocal hyperspectral microscopic imager for the detection and classification of individual microalgae.

We propose a confocal hyperspectral microscopic imager (CHMI) that can measure both transmission and fluorescent spectra of individual microalgae, as well as obtain classical transmission images and corresponding fluorescent hyperspectral images with a high signal-to-noise ratio. Thus, the system can realize precise identification, classification, and location of microalgae in a free or symbiosis state. The CHMI works in a staring state, with two imaging modes, a confocal fluorescence hyperspectral imaging (CFHI) mode and a transmission hyperspectral imaging (THI) mode. The imaging modes share the main light path, and thus obtained fluorescence and transmission hyperspectral images have point-to-point correspondence. In the CFHI mode, a confocal technology to eliminate image blurring caused by interference of axial points is included. The CHMI has excellent performance with spectral and spatial resolutions of 3 nm and 2 µm, respectively (using a 10× microscope objective magnification). To demonstrate the capacity and versatility of the CHMI, we report on demonstration experiments on four species of microalgae in free form as well as three species of jellyfish with symbiotic microalgae. In the microalgae species classification experiments, transmission and fluorescence spectra collected by the CHMI were preprocessed using principal component analysis (PCA), and a support vector machine (SVM) model or deep learning was then used for classification. The accuracy of the SVM model and deep learning method to distinguish one species of individual microalgae from another was found to be 96.25% and 98.34%, respectively. Also, the ability of the CHMI to analyze the concentration, species, and distribution differences of symbiotic microalgae in symbionts is furthermore demonstrated.

Improvement of carotenoid extraction from a recently isolated, robust microalga, Tetraselmis sp. CTP4 (chlorophyta).

In recent years, there has been increasing consumer interest in carotenoids, particularly of marine sustainable origin with applications in the food, cosmeceutical, nutritional supplement and pharmaceutical industries. For instance, microalgae belonging to the genus Tetraselmis are known for their biotechnologically relevant carotenoid profile. The recently isolated marine microalgal strain Tetraselmis sp. CTP4 is a fast-growing, robust industrial strain, which has successfully been produced in 100-m3 photobioreactors. However, there are no reports on total carotenoid contents from this strain belonging to T. striata/convolutae clade. Although there are several reports on extraction methods targeting chlorophytes, extraction depends on the strength of cell coverings, solvent polarity and the nature of the targeted carotenoids. Therefore, this article evaluates different extraction methods targeting Tetraselmis sp. CTP4, a strain known to contain a mechanically resistant theca. Here, we propose a factorial experimental design to compare extraction of total carotenoids from wet and freeze-dried microalgal biomass using four different solvents (acetone, ethanol, methanol or tetrahydrofuran) in combination with two types of mechanical cell disruption (glass beads or dispersion). The extraction efficiency of the methods was assessed by pigment contents and profiles present in the extracts. Extraction of wet biomass by means of glass bead-assisted cell disruption using tetrahydrofuran yielded the highest amounts of lutein and ß-carotene (622 ± 40 and 618 ± 32 µg g-1 DW, respectively). Although acetone was slightly less efficient than tetrahydrofuran, it is preferable due to its lower costs and toxicity.

Morphological characterization, growth appraisal, and probing biofuels potential of newly isolated Scenedesmus sp. from desert Cholistan.

Microalgae have an excellent potential for producing valuable natural products, including biofuels. Therefore, it is imperative to explore and document the existing microalgal flora and utilize their potentials to cope the increasing human needs. The present work aims at exploring and characterizing newly isolated microalgae from desert Cholistan, a habitat with myriad algal diversity. Light microscopy, scanning electron microscopy, and molecular phylogenetic approaches were used for species-level identification. Characterization and growth optimization of Scendesmus sp. were analyzed under three different growth modes to determine the most favorable conditions for increasing biomass, growth rate, and lipid content. The results revealed that mixotrophic (MT) mode significantly increases photosynthetic activity, growth rate, and lipid content with glycerol as supplement carbon source. The investigated Scenedesmus dimorphous produced a maximum dry weight of 1.73 g L-1 , improved fatty acid methyl esters profile and yield lipid up to 40% of DCW (68 g L-1 ) under MT mode, which is almost double to that of photoautotrophic cultivation. The glycerol availability in medium has been identified as the critical element for boosting growth and lipid content. Thus, it can reduce the cost of biofuel production.

Microalgae in modern cancer therapy: Current knowledge.

Cancer is an everyday medical concern which requires an appropriate treatment strategy. The malfunction of cell cycle is a well-established cause for cancer induction. Chemotherapy and radiation are the standard available therapeutic approach for cancer treatment; however severe side effects were reported in association to such treatments, for instance, the efficacy of patients' immune system is adversely affected in apart by radiation. These side effects may be minimized by providing novel remedial preparations. Complementary and alternative medicinal compounds, which were obtained from fresh or marine flora particularly micro and macro algae, were reported to its anti-cancerous activities. Several types of bioactive molecules are also present in microalgae, such as carotenoids, various forms of polysaccharides, vitamins, sterol, fibres, minerals…ect; the great unused biomass of microalgae and their excellent diversity of chemical constituents may introduce a major step in developing of anti-malignant drugs. Previously, such characteristic of microalgal bio-diversity was commercially exploited to make food supplements and gelling substances. However, recently, several investigations were designed to study the potential anti-carcinogenic effect of microalgal extracts, where they mostly concluded their ability to induce apoptotic cancer cell death via caspase dependent or independent pathways. In this review paper, we reported the various species of microalgae that possessed anti-tumor activity, the tumor cell lines altered through using microalgal extracts along with the levels of such extracts that reported to its inhibitor effect against cell cycle and proliferation.

Fractional conversion of microalgae from water blooms.

Fractional conversion of natural algae cyanobacteria from Taihu Lake was conducted. The raw Taihu Lake algae (TLA) and pretreated samples were pyrolyzed at 290 °C and 450 °C according to the TGA results. Extraction of lipids or saccharides from the TLA was performed as a pretreatment to obtain lipid extracted algae (LEA) or saccharide extracted algae (SEA). The total yields of bio-oil from fractional pyrolysis were 40.9 wt% from TLA, 42.3 wt% from LEA, and 48.5 wt% from SEA. From TLA, the major components of the bio-oil were fatty acids, amides and hydrocarbons (heptadecane) at 290 °C whereas those at 450 °C were phenols and C10-C15 hydrocarbons. Following the lipid extraction, acids, amides and indoles accounted for a large proportion at 290 °C, while the main products obtained at 450 °C were phenols, indoles and pyrroles. It is worth mentioning that the yield of bio-oil from the LEA had increased, and the composition of the bio-oil was simplified. Moreover, the average molecular weight of the bio-oil obtained from LEA had decreased. Interestingly, the extraction of saccharides inhibited pyrolysis of the lipids, so the distribution of the bio-oil from SEA changed only a little. Fractional pyrolysis of pretreated microalgae not only increased the bio-oil yield but also improved the quality of the bio-oil.

Potential application of microalga Spirulina platensis as a protein source.

The high protein level of various microalgal species is one of the main reasons to consider them an unconventional source of this compound. Spirulina platensis stands out for being one of the richest protein sources of microbial origin (460-630 g kg-1 , dry matter basis), having similar protein levels when compared to meat and soybeans. The use of S. platensis in food can bring benefits to human health owing to its chemical composition, since it has high levels of vitamins, minerals, phenolics, essential fatty acids, amino acids and pigments. Furthermore, the development of new protein sources to supply the shortage of this nutrient is an urgent need, and protein from S. platensis plays an important role in this scenario. In this sense, extraction processes that allow maximum protein yield and total utilization of biomass is an urgent need, and ultrasonic waves have proven to be an effective extraction technique. The number of scientific papers related to protein fraction from S. platensis is still limited; thus further studies on its functional and technological properties are needed. © 2016 Society of Chemical Industry.

Microalgae harvesting by pH adjusted coagulation-flocculation, recycling of the coagulant and the growth media.

Coagulation-flocculation can be considered as one of the least energy intensive microalgae biomass harvesting processes. However, cost of the coagulant and biomass contamination are two critical issues that need to be considered. In this study, ferric chloride (72-96mg/L) was used to effectively harvest Scenedesmus sp. (530mg/L) - grown in BG-11 media and wastewater. Reducing the culture pH below 6.5, greatly improved the harvesting efficiency. Acidic solution (pH 1.0) was very effective to recover (almost 90%) the associated iron from the harvested biomass. Scenedesmus sp. was able to grow in the supernatant and utilize the residual iron in it. Iron extracted solution, with a supplementation of 9.8mg/L ferric chloride, was able to achieve similar harvesting efficiency. The potential recovery of iron from the harvested biomass and its reuse in the harvesting can improve the biomass quality for subsequent downstream processing while reducing the cost.

Microalgae removal with Moringa oleifera.

Moringa oleifera seed extract was tested for algae (Chlorella, Microcystis, Oocystis and Scenedesmus) removal by Jar-test technique. This coagulant can be used in drinking water treatment. Jar-test has been carried out in order to evaluate the efficiency of this natural coagulant agent inside real surface water matrix. The influence of variables has been studied in this process, including operating parameters such as coagulant dosage, initial algae concentration, pH, agitation time and water matrix. Removal capacity is verified for water with high contamination of algae while the process is not affected by the pH and water matrix. Coagulation process may be modelling through Langmuir and Freundlich adsorption hypothesis, so acceptable r2 coefficients are obtained.

UPLC-MSE profiling of Phytoplankton metabolites: application to the identification of pigments and structural analysis of metabolites in Porphyridium purpureum.

A fast and high-resolution UPLC-MSE analysis was used to identify phytoplankton pigments in an ethanol extract of Porphyridium purpureum (Pp) devoid of phycobiliproteins. In a first step, 22 standard pigments were analyzed by UPLC-MSE to build a database including retention time and accurate masses of parent and fragment ions. Using this database, seven pigments or derivatives previously reported in Pp were unequivocally identified: ß,ß-carotene, chlorophyll a, zeaxanthin, chlorophyllide a, pheophorbide a, pheophytin a, and cryptoxanthin. Minor amounts of Divinyl chlorophyll a, a chemotaxonomic pigment marker for prochlorophytes, were also unequivocally identified using the database. Additional analysis of ionization and fragmentation patterns indicated the presence of ions that could correspond to hydroxylated derivatives of chlorophyll a and pheophytin a, produced during the ethanolic extraction, as well as previously described galactosyldiacylglycerols, the thylakoid coenzyme plastoquinone, and gracilamide B, a molecule previously reported in the red seaweed Gracillaria asiatica. These data point to UPLC-MSE as an efficient technique to identify phytoplankton pigments for which standards are available, and demonstrate its major interest as a complementary method for the structural elucidation of ionizable marine molecules.

Isolation and characterization of microalgae for biodiesel production from seawater.

As green marine microalgae isolated from local seawater in Tianjin, China, Nannochloropsis gaditana Q6 was tolerant to the variation of salinity with the highest biomass and lipid concentration in natural seawater medium. Although this strain could grow mixotrophically with glycerol, the narrow gap between mixotrophic and autotrophic cultivation suggested that autotrophic cultivation was the optimal trophic type for N. gaditana Q6 growth. In addition, strain Q6 was more sensitive to the variance of NH4HCO3 concentration than NaH2PO4 concentration. Consequently, the lipid production could be maximized by the two-stage cultivation strategy, with an initial high NH4HCO3 concentration for biomass production followed by low NH4HCO3 concentration for lipid accumulation.

Nutrient removal and lipid accumulation properties of newly isolated microalgal strains.

In this work, four microalgae including Chlorella sp. SDEC-10, Chlorella ellipsoidea SDEC-11, Scenedesmus bijuga SDEC-12 and Scenedesmus quadricauda SEDC-13 isolated from a local lake have been investigated for the properties of growth, nutrient removal and lipid accumulation in synthetic sewage. Their biomass ranged between 0.4 and 0.5g/L. The total phosphorus removal efficiency of four strains was nearly 100%, but in the case of total nitrogen and ammonium the removal efficiency was relatively low. Their lipid content, ranging from 25.92% to 27.76% and corresponding to the lipid productivity 7.88-18.08mg/L/d, was higher than that obtained in BG-11. Palmitic acid and oleic acid were the predominant compositions found through fatty acids analysis. S. quadricauda SDEC-13 performed best both in nutrient removal and in lipid production among the four strains.

Optimization of cationic amino starch synthesis using biogenic amines.

Harvesting microalgae presents a challenge in selecting the most economical method for low cost algal bioproducts. Previous studies have shown coagulation-flocculation to be the most efficient method for large scale microalgae harvesting. This study focused on modifying native potato starch with biogenic amines and optimizing the reaction parameters. Such modification rendered the starch cationic, with an ability to destabilize microalgae suspensions or colloids. The effect of time, temperature, and reactant concentrations on the zeta potential of the cationic amino starch was studied. Biogenic amines including putrescine, histamine, cadaverine, and tyramine were selected for study based on the number of nitrogen groups in their structure. Zeta potential for histamine cationic amino starch was significantly higher (+9.0±2.0 mV) at lower reaction temperatures, regardless of the amine to starch ratio and reaction time intervals. Putrescine, cadaverine, and tyramine cationic amino starches exhibited significantly higher zeta potential values (13.76±3.60, 6.81±1.64, and 5.68±1.60 mV, respectively) with amine to starch ratio higher than reaction stoichiometry, irrespective of reaction temperature or time intervals. This optimization study has presented a basis for designing reaction conditions for the synthesis of cationic amino starch from an inhomogeneous mix of biogenic amines derived from waste sources.

Selection and evaluation of CO2 tolerant indigenous microalga Scenedesmus dimorphus for unsaturated fatty acid rich lipid production under different culture conditions.

Five indigenous microalgal strains of Scenedesmus, Chlorococcum, Coelastrum, and Ankistrodesmus genera, isolated from Indian fresh water habitats, were studied for carbon-dioxide tolerance and its effect on growth, lipid and fatty acid profile. Scenedesmus dimorphus strain showed maximum growth (1.5 g/L) and lipid content (17.83% w/w) under CO2 supplementation, hence selected for detailed evaluation. The selected strain was alkaline adapted but tolerated (i) wide range of pH (5-11); (ii) elevated salinity levels (up to 100 mM, NaCl) with low biomass yields and increased carotenoids (19.34 mg/g biomass); (iii) elevated CO2 levels up to 15% v/v with enhancement in specific growth rate (0.137 d(-1)), biomass yield (1.57 g/L), lipid content (19.6% w/w) and CO2 biofixation rate (0.174 g L(-1) d(-1)). Unsaturated fatty acid content (alpha linolenic acid) increased with CO2 supplementation in the strain.

Nutrient sequestration, biomass production by microalgae and phytoremediation of sewage water.

The present work was aimed at analysing the role of inoculated microalgae in nutrient dynamics, bioremediation and biomass production of sewage water. Preliminary microscopic analyses of sewage water revealed the presence of different algal groups, with predominance of Cyanophyta. Among the inoculated strains, Calothrix showed highest dry cell weight (916.67 mg L(-1)), chlorophyll and carotenoid content in tap water + sewage water (1:1) treatment. Significant removal of NO3-N ranging from 57-78% and PO4-P (44-91%) was recorded in microalgae inoculated tap water + sewage water. The total dissolved solids and electrical conductivity of tap water + sewage water after incubation with Calothrix sp. decreased by 28.5 and 28.0%, accompanied by an increase in dissolved oxygen from 4.4 to 6.4 mg L(-1) on the 20th day. Our investigation revealed the robustness of Calothrix sp. in sequestering nutrients (N and P), improving water quality and proliferating in sewage water.

Nutrient removal from membrane bioreactor permeate using microalgae and in a microalgae membrane photoreactor.

This paper explores the use of a novel microalgae membrane photoreactor (mMR) to polish the effluent from an aerobic membrane bioreactor (MBR) fed with domestic wastewater. Four microalgae species Chlorella (Chlorella sp.), Chlorella vulgaris (C. vulgaris), Scenedesmus quadricauda (S. quadricauda) and Scenedesmus dimorphus (S. dimorphus) were isolated from the environment and tested in batch reactors fed with permeate from the aerobic MBR to evaluate the nutrient removal rates for each species. All four microalgae species were able to completely remove NH4 in the reactor within 3 days. The removal rates of NO3, NO2 and PO4 were between 43-54%, 83-95% and 70-92%, respectively after 3 days in the batch reactor. Subsequently, an MBR-mMR system was operated for 23 days. The mMR was able to remove on average 50% of NH4, 75% of NO2, 35% of NO3 and 60% of PO4 consistently from the MBR effluent under the conditions tested.

Effect of light, nutrient, cultivation time and salinity on lipid production of newly isolated strain of the green microalga, Botryococcus braunii KMITL 2.

The green microalga strain, Botryococcus braunii KMITL 2, was isolated from a freshwater reservoir in central Thailand, and the effects of light, nitrogen, phosphorus, iron, cultivation time and salinity on lipid production were studied by varying parameters one at a time. When cultured in Chlorella medium containing 222 mg L(-1) phosphorus (PO(4)(3-)-P) under continuous illumination of 200 µE m(-2)s(-1) with a salinity of 0 psu, a maximum lipid content of 54.69 ± 3.13% was obtained. Its high lipid content makes strain KMITL 2 a potential source for biodiesel production in tropical regions.

Algal diversity in flowing waters at an acidic mine drainage "barrens" in central Pennsylvania, USA.

Microscopic investigations were undertaken to decipher the diversity in the lotic algal communities from acidic waters (pH 2.4-3.2) flowing overland in sheets and channels at an acid mine drainage (AMD) barrens near Kylertown, PA, USA. Microscopic observations, supplemented with taxonomic keys, aided in identification of the dominant algae, and measurement of carbon from adjacent soils was undertaken. The unicellular protist Euglena sp. was most abundant in slower flowing waters (i.e., pool near point of emergence and surficial flow sheets), while Ulothrix sp. was most abundant in faster flowing water from the central stream channel. A diverse range of unicellular microalgae such as Chlorella, Cylindrocystis, Botryococcus, and Navicula and several filamentous forms identified as Microspora, Cladophora, and Binuclearia were also recorded. The observed high algal diversity may be related to the long duration of AMD flow at this site which has led to the development of adapted algal communities. The comparatively higher carbon content in soil materials adjacent to slower flowing water sampling locations provides evidence for the important role of algae as primary producers in this extreme environment.

Isolation of a new strain of Picochlorum sp and characterization of its potential biotechnological applications.

Selection of new autochthon strains is necessary, and for the moment the best strategy, to find microalgae well adapted to the local climatological conditions able to simultaneously produce several compounds of biotechnological interest and grow at high rates. We describe the isolation and characterization of a new microalgal strain isolated from the marshlands of the Odiel River in the Southwest of Spain. The new microalga belongs to the genus Picochlorum, as deduced from the analysis of its 18S rRNA encoding gene, is able to grow at a high growth rate and thrive with adverse conditions. It has an appreciable constitutive level of lutein (3.5 mg g(-1) DW) and zeaxanthin (0.4 mg g(-1) DW) which is increased to 1.8 mg g(-1) DW at high light intensities. This strain is also characterized by a very low level of linolenic acid (3.8% of total fatty acids) and no polyunsaturated fatty acids with four or more double bonds. Although the total lipid content is not particularly high, 23% of the dry weight, its fatty acid profile makes of Picochlorum sp HM1 a promising candidate for biodiesel production, and the high content in the carotenoids lutein and zeaxanthin indicates that the microalga could also be a good source for natural eye vitamin supplements, which could be obtained as co-products.

Local bioprospecting for high-lipid producing microalgal strains to be grown on concentrated municipal wastewater for biofuel production.

Mass cultivation of microalgae for biofuel production depends heavily on the performance of the microalgae strains used. In this study, 60 algae-like microorganisms collected from different sampling sites in Minnesota were examined using multi-step screening and acclimation procedures to select high-lipid producing facultative heterotrophic microalgae strains capable of growing on concentrated municipal wastewater (CMW) for simultaneous energy crop production and wastewater treatment. Twenty-seven facultative heterotrophic microalgae strains were found, among which 17 strains were proved to be tolerant to CMW. These 17 top-performing strains were identified through morphological observation and DNA sequencing as Chlorella sp., Heynigia sp., Hindakia sp., Micractinium sp., and Scenedesmus sp. Five strains were chosen for other studies because of their ability to adapt to CMW, high growth rates (0.455-0.498 d(-1)) and higher lipid productivities (74.5-77.8 mg L(-1)d(-1)). These strains are considered highly promising compared with other strains reported in the literature.