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Most studies of terrestrial bryophytes as natural substrates for photosynthetic microorganisms have been performed in the polar regions, where bryophytes are an important part of the ecosystem. As they remain green throughout the year, bryophytes may also be an ideal substrate for epiphytic organisms in temperate regions. The present study investigated the colonization potential and diversity of microalgae on selected plant species in riparian forest and spruce monoculture in a temperate region. It examines whether the presence of algae is related to substrate humidity, the micromorphology of gametophyte or the seasonal availability of substrate. The taxonomic diversity of algae was studied. Cyanobacteria and green algae were cultured on BG-11 agar medium, while diatoms were identified in permanent diatomaceous slides. The alpha- and beta-diversity indices were calculated, and the communities were compared using Bray-Curtis distances and multidimensional correspondence analyses. Our findings indicate that the largest number of alga species were diatoms; however, their presence was only observed in riparian forest and was associated with high humidity. Both aerophilic and freshwater taxa were noted, the latter carried by water from nearby aquatic ecosystem. Green algae were present in both phytocoenoses and humidity appears to have no substantial effect on the degree of colonization; their diversity was low and the group consisted of terrestrial taxa. In two bryophytes growing at the highest humidity, cyanobacteria were only identified in culture. The key factor influencing the degree of microalgae colonization was the humidity of the substrate, which was related to the distance from water. [ABSTRACT FROM AUTHOR]

Microalgal-biofilm culture has the advantages of less water requirement and higher lipid productivity. For efficient lipid production in an aerial phase condition, it is ideal to simultaneously induce microalgal biofilm growth and lipid accumulation. Biomass production and lipid accumulation in the aerial microalga Coccomyxa subellipsoidea KGU-D001 were investigated in the logarithmic growth phase. Initially, the alga was cultured in three different conditions: in liquid phase using Bold's basal medium (BBM), and in the aerial phase in the presence or absence of BBM. In aerial phase conditions with nutrients (i.e., BBM), biomass production was prioritized over cell proliferation until approximately the 7th day of culture. In the liquid phase conditions, the ratio of total organic carbon to total nitrogen (C/N) in cells was almost constant during the culture period. However, in both aerial phase conditions, the C/N ratio increased during the culture period, more so in the absence of nutrients. The total fatty acid content also increased throughout the culture period. Then, algal cells were cultured for a 17-day culture; there would be a growth period of 10 days followed by a lipid accumulation period of 7 days. In such cultures in the presence of BBM, the biomass and lipid productivities (388 and 94.2 mg/m2/day) were both significantly higher in the aerial phase than in the liquid phase during the lipid production period. C. subellipsoidea can produce lipids even during growth if the CO2 supply is efficient and the C/N ratio is high. [ABSTRACT FROM AUTHOR]

Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O2 which diminishes the expression and the activity of the hydrogenase enzyme catalyzing H2 production. Here we report a third, hitherto unknown challenge: We found that under anoxia, a slow-down switch is activated in photosystem II (PSII), diminishing the maximal photosynthetic productivity by three-fold. Using purified PSII and applying in vivo spectroscopic and mass spectrometric techniques on Chlamydomonas reinhardtii cultures, we show that this switch is activated under anoxia, within 10 s of illumination. Furthermore, we show that the recovery to the initial rate takes place following 15 min of dark anoxia, and propose a mechanism in which, modulation in electron transfer at the acceptor site of PSII diminishes its output. Such insights into the mechanism broaden our understanding of anoxic photosynthesis and its regulation in green algae and inspire new strategies to improve bio-energy yields. H2 generation from Chlamydomonas reinhardtii cultured under anoxia is found to be limited by activation of a slow-down switch in photosystem II that modulates electron transfer at the acceptor site of this photosystem following light exposure. [ABSTRACT FROM AUTHOR]

Dynamic light regimes strongly impact microalgal photosynthesis efficiency. Finding the optimal way to supply light is then a tricky problem, especially when the growth rate is inhibited by overexposition to light and, at the same time, there is a lack of light in the deepest part of the culture. In this paper, we use the Han model to study the theoretical microalgal growth rate by applying periodically two different light intensities. Two approaches are considered depending on the period of the light pattern. For a large light period, we demonstrate that the average photosynthetic rate can be improved under some conditions. Moreover, we can also enhance the growth rate at steady state as given by the PI-curve. Although, these conditions change through the depth of a bioreactor. This theoretical improvement in the range of 10–15% is due to a recovery of photoinhibited cells during the high irradiance phase. We give a minimal value of the duty cycle for which the optimal irradiance is perceived by the algae culture under flashing light regime. [ABSTRACT FROM AUTHOR]

As the severity of extreme precipitation events increases with global climate change, so will episodic pulses of contamination into lotic systems. Periphytic algae represents bioindicator species in most freshwater systems due to their rapid accumulation of toxicants; therefore, it is vital to understand how accumulation in this group differs across temporally variable exposure regimes. The ability to rapidly accrue contaminants has additional implications for the trophic transfer of metals to primary consumers. While dietary toxicity has been studied in algivorous consumers, techniques used to prepare contaminated periphytic algae for consumption have not been compared. This study used a modified subcellular fractionation method to compare the partitioning of zinc (Zn) in periphyton cultures exposed for various durations (cultured in the presence of Zn and 15 min, 24 h, and 48 h exposures). Three exposure groups were additionally depurated over a period of 24 h in order to compare retention of Zn, an important aspect of preparing diets used in dietary toxicity studies. The results not only provide evidence for increased retention by periphytic algae cultured in the presence of Zn but reveal relationships among treatments and subcellular partitioning that suggest time-dependent accumulation and detoxification. These relationships suggest that episodic exposure of periphytic algae to contaminants may pose a greater risk than that of chronic regimes. Based on these results, we additionally advocate for culturing periphytic algae in the presence of contamination to produce a more reliable diet for dietary exposure testing in algivorous organisms. [ABSTRACT FROM AUTHOR]

Contamination of microalgae cultures can reduce their productivity and affect the quality of biomass and valuable bioproducts. In this article, after having isolated and identified for the first time the filamentous fungus Penicillium citrinum from heterotrophic cultures of the red polyextremophilic microalga Galdieria sulphuraria, we investigated the biological and metabolic significance of this alga-fungus association. In the same medium, both organisms grow better in each other's presence than separately. Both cell density and cell size of G. sulphuraria increase in co-cultures compared to pure alga cultures. In co-cultures, despite very severe growth conditions, the load of P. citrinum increases compared to pure fungus cultures. Optical microscope images have shown physical contact between cells of P. citrinum hyphae and G. sulphuraria which, however, retain their morphology and cell wall intact. GC–MS-based metabolomics analysis of metabolites excreted in the culture medium shows that pure cultures of the fungus and alga and co-cultures of alga plus fungus can be easily differentiated based on their metabolic products. Indeed, a richer assortment of extracellular metabolites (comprising both products of primary and secondary metabolism) is a distinct feature of co-cultures compared to both pure alga and pure fungus cultures. [ABSTRACT FROM AUTHOR]

The functional state of an enrichment culture of a green alga Coelastrella multistriata (Trenkwalder) Kalina et Puncochárová in the course of 60-day cultivation was studied. The concentrations of chlorophylls a, b, and c, total carotenoids, protein, vitamins A and E were determined. The rates of lipid peroxide oxidation in the cells of C. multistriata strain MZ–Ch23 were determined using the concentrations of peroxidation products reacting with 2-thiobarbituric acid. The concentrations of these products were determined in the algal biomass on days 15, 25, and 60 of cultivation in the BBM medium, as well as after initiation of peroxide oxidation with Fe2+. Among the photosynthetic pigments, the highest content (14.82 mg/g dry biomass) was shown for chlorophyll a during the exponential growth phase. The total amount of carotenoids was comparable to the values for other studied Coelastrella strains, 0.74–4.21% of the dry biomass. Strain MZ–Ch23 was shown to accumulate high concentrations of retinol (170.49–586.09 µg/L of the algal culture) and protein (141.81–212.38 mg/L). While during all phases of the cultivation C. multistriata cells exhibited low concentrations of the products of lipid peroxide oxidation (0.005–0.015 nmol/mg protein), initiation of peroxide oxidation increased the concentration of TBA-active products up to 0.187 nmol/mg protein on day 60. Cultivation in BBM medium for 25 days proved to be the optimal strategy for obtaining C. multistriata biomass enriched with secondary metabolites and resistant to peroxide oxidation. This resulted in significant amounts of the biomass with high levels of carotenoids, protein, and vitamin A. [ABSTRACT FROM AUTHOR]

In the field of industrial microalgae production, the introduction of parasitic contaminants is an often-neglected topic, but one that represents a major risk with potentially significant financial implications. So far, no successful strategy exists to maintain a long-term stable cultivation environment in industrial photobioreactors. To create a strategy for preventing and controlling parasitic contamination, methods from synthetic ecology were used, replacing monocultures with mixed-biocoenoses. The goals were the identification of microbiotic ecosystems of potentially symbiotic bacteria and the utilization of synergistic effects between bacteria and algae to stabilize cultures. The final aim was to combine the findings with abiotic factors influencing the infections. As model organisms, the microalga Coelastrella vacuolata (formerly Scenedesmus vacuolatus) and the parasitic contaminant Amoeboaphelidium protococcarum were chosen. For this case, a correlation between infection rate and the chlorophyll a fluorescence in the culture was found. Algal co-cultures with specific bacteria were tested using the protecting effects of antiphytopathogenic, extracellular substances. This led to the bacterium Pseudomonas protegens and the naturally antipathogenic phenol 2,4-diacetylphloroglucinol (DAPG). Co-cultures with DAPG-producing P. protegens effectively inhibited the infection even though no quantifiable amounts of DAPG were found in the culture. Furthermore, abiotic influences on the infection process were identified, resulting in the implementation of a light–dark-cycle with induced anaerobic conditions in the dark phase. With these findings, conditions that inhibit the growth of parasitic contaminants could now be introduced preventively within standard cultivation procedures. [ABSTRACT FROM AUTHOR]

The production of diadinoxanthin and its cytostatic activity in an intensive culture of C. closterium has been estimated via molecular modeling and experiments with the human tumor cell cultures OVCAR5, OVCAR8, KURAMOCHI, and OVSAHO. According to data from both the simulation and experiments with the cell cultures, diadinoxanthin demonstrates lower activity (by more than four times) in comparison with fucoxanthin. The IC50 value for diadinoxanthin is achieved at a concentration of more than 100 μM, while fucoxanthin exhibits a cytostatic effect below 18.75 μM. In a flow-through culture of C. closterium, the production of diadinoxanthin can exceed the production of fucoxanthin by 14 times, which can make the technology for its production less expensive and can significantly reduce the cost of therapeutic and prophylactic drugs based on microalgae. [ABSTRACT FROM AUTHOR]

The amphipod Sunamphitoe namhaensis grazes on seedlings of Sargassum horneri in culture. To exterminate S. namhaensis, we immersed them in seawater with dissolved carbon dioxide—a treatment used previously to remove copepods in cultures of abalone and sea cucumber. Experiments were conducted under different CO2 (aq) concentrations and for different lengths of time. Amphipod mortality was 100% following immersion in CO2 seawater with a CO2 (aq) concentration of 26,262 µmol/kg (pH 5.0) for 60 min. When algal seedlings were immersed in CO2 seawater under these same conditions, their survival rate and growth were not affected. [ABSTRACT FROM AUTHOR]

This study aimed at exploring microalgal heterogeneity from fresh water samples collected from inland water bodies in the heavily built city of Singapore. Culturable pure isolates (n = 94) were subject to an in-house microalgal DNA extraction method and LSU rDNA sequencing. Isolates were analysed for their predominance and distribution. A total of 17 different algal genera were identified (H = 2.8, EH = 0.6), of which Scenedesmus spp. and Chlorella spp. constituted 27.5% and 21.3% of isolates respectively, followed by Micractinium spp. (18.8%) and Chlamydomonas spp. (12.5%). We also report 16 new microalgal strains from this region. The data is important from an ecological and biotechnological perspective. [ABSTRACT FROM AUTHOR]

Open looped channels are an energy-efficient and low-cost solution often adopted for the cultivation of algae. These channels are commonly composed by two parallel straight channels interconnected by two curving sections and, as such, are referred as raceway ponds. The scaling up of algae production systems, usually associated with novel usages of algal products, has created new challenges for raceway-based cultivation systems. In particular, the uncertainties of cultivating novel algae cultures, e.g. macroalgae for which optimal inland cultivation conditions are still under-researched, impose further demands for raceway design and operation. Versatile operational conditions for raceways may be thus desirable for pioneering inland cultivation systems for certain species, applications and climate conditions. In this work, raceways of standard design are evaluated in terms of geometry, specifically raceway length, width and operational conditions, i.e. flow depth and operational velocity, with the use of a CFD tool. The hydrodynamic performance of the studied cases is analysed based on velocity uniformity and power consumption. [ABSTRACT FROM AUTHOR]

Oleaginous microalgae with high biomass productivity, lipid content, and lipid productivity are desirable for sustainable biofuel production. Rapid and accurate quantification of lipid content facilitates the identification of promising microalgae candidates. In the present study, 23 freshwater microalgae species from river Noyyal were isolated and identified based on their morphological and molecular (18S rRNA) features and recorded as Karunya Algae Culture Collection (KACC). Their biomass and lipid content were characterized and screened using FT-IR, Nile red staining, and gravimetric method. Results generated from FT-IR spectra differentiated KACC microalgae based on their biochemical contents with Scenedesmus rubescens KACC 2 and Chlorococcum sp. KACC 13 possessed high total protein and lipid content, respectively. Nile red fluorescence at 530/575 nm showed the yellow fluorescence under a fluorescent microscope giving the evidence of high neutral lipids in 10 KACC microalgae isolates. Total lipid content showed prominent variation between the KACC isolates and found in the range of 4 to 32% of DW. Lipid productivity and biomass productivity showed a similar pattern among KACC strains. Thus, our findings serve as a baseline data on the bioprospecting potential of KACC isolates from river Noyyal, an unexplored area of Western Ghats. [ABSTRACT FROM AUTHOR]

This article describes a modification of the spectrophotometric method for the determination of chlorophyll a in seston (suspended matter), which is convenient for hydroecological monitoring. It is proposed to use nuclear filters, as they have a number of advantages over fiberglass and bulk filters. An important difference of our approach from the standard methods is the use of the short-term (up to 30 min) drying of nuclear filters with seston in a desiccator at a temperature of 50–55oC immediately after the suspended matter is deposited on the filter. A comparative analysis of the standard methodology and the proposed modification for assessing the content of chlorophyll and phaeopigments in laboratory cultures of algae (Euglena gracilis, Chlorella vulgaris) and natural plankton from a natural reservoir was carried out. [ABSTRACT FROM AUTHOR]

Wastewater rich in organic carbon, nitrogen and phosphorus may serve as a convenient source of carbon and nutrients for a year-long microalgae production. Scientific reports indicate that some single-cell microalgae such as Chlorella and Scenedesmus, are highly tolerant to wastewater environments and efficiently remove biogenic compounds. The aim of this study was to determine the possibility of using the effluent produced in the process of anaerobic degradation of whey as a culture medium for the multiplication of Chlorella vulgaris algae biomass and to characterise their growth efficiency and rate. The content of nitrogen and phosphorus in wastewater was sufficient for conducting an effective culture of algae. The efficiency of nitrogen removal in the flow system was 15.61 ± 1.38 mg N/dm3/day. [ABSTRACT FROM AUTHOR]

Microalgae can accumulate large proportions of their dry cell weight as storage lipids when grown under appropriate nutrient limiting conditions. While a high ratio of carbon to nitrogen is often cited as the primary mode of triggering lipid accumulation in microalgae, fast optimization strategies to increase lipid production for mixotrophic cultivation have been difficult to developed due to the low cell densities of algal cultures, and consequently the limited amount of biomass available for compositional analysis. Response surface methodologies provide a power tool for assessing complex relationships such as the interaction between the carbon source and nitrogen source. A 15 run Box-Behnken design performed in shaker flasks was effective in studying the effect of carbon, nitrogen, and magnesium on the growth rate, maximum cell density, lipid accumulation rate, and glucose consumption rate. Using end-point dry cell weight and total lipid content as assessed by direct transesterification to FAME, numerical optimization resulted in a significant increase in lipid content from 18.5 ± 0.76% to 37.6 ± 0.12% and a cell density of 5.3 ± 0.1 g/L to 6.1 ± 0.1 g/L between the centre point of the design and the optimized culture conditions. The presented optimization process required less than 2 weeks to complete, was simple, and resulted in an overall lipid productivity of 383 mg/L·d. [ABSTRACT FROM AUTHOR]

The potential of microalgae as a biofertilizer in agriculture is increasingly recognized. We studied the effect of applications of Chlorella on growth of wheat in terms of its phytostimulating capacity and its potential for substituting chemical fertilizers. Four biofertilizer treatments were used in this experiment: (i) Biomass of Chlorella sorokiniana harvested by centrifugation from cultures in the exponential growth phase and re-suspended in spent growth medium (Solution 1); (ii) filtered BG11 medium used for algae culture after the algae biomass was harvested (Solution 2); (iii) harvested algae that were re-suspended in fresh BG11 medium (Solution 3); and (iv) fresh BG11 medium (Control). Seeds of Triticum aestivum were germinated in pots containing a growing substrate (peat vermiculite 1:1 (v/v) mixture) and grown for 15 days with applications of the four treatments solutions. In general, plant length was increased by 30% with Solution 2; total dry biomass of aboveground and belowground parts were improved by 22% and 51%, respectively, in treatments with filtrate of Chlorella sorokiniana (Solution 2), as compared to the control, indicating that nutrients and extracellular substances excreted by algae in the filtrate were pertinent to the beneficial effects on plant growth. [ABSTRACT FROM AUTHOR]

The alga Chlorella sorokiniana was cultivated under natural conditions of St. Petersburg with natural lighting, without aeration, and with stirring once per day. The controls were strains of the populations grown under laboratory conditions at a stable temperature under the same aeration conditions and also with aeration and periodic stirring. The main cultivation conditions affecting cell multiplication were aeration and stirring. Algal cells multiplied 3.5 times in 16 days under these conditions and about doubled under natural conditions of St. Petersburg. Negative environmental impacts manifested as an increased proportion of dead cells in the population that was found by methylene-blue staining of temporary medications. Thus, C. sorokiniana could be cultivated under St. Petersburg conditions. However, cultivation conditions with aeration and periodic stirring had to be adjusted. A scheme for using algae cultivated under St. Petersburg conditions to produce valuable components and biofuels was proposed. [ABSTRACT FROM AUTHOR]

Living cultural strains of the green algae 'Chlorella' mirabilis and Muriella terrestris have been isolated from buried soils, and their identification has been confirmed by morphological and molecular-genetic analysis. It has been shown that the retention of their viability could be related to their small size and the presence of sporopollenin in cell walls. The effect of methods for the reactivation of dormant microbial forms on the growth of algae in paleosols has been estimated. The total DNA content has been determined in buried and recent background soils, and relationship between DNA and the presence and age of burial has been established. [ABSTRACT FROM AUTHOR]

Effect of salinity on vegetative growth and sexual reproduction was investigated in laboratory cultures of a benthic diatom Ardissonea crystallina (C. Agardh) Grunow from the Black Sea and vegetative growth of Ardissonea sp. from the coast of Martinique, the Atlantic Ocean. Typical water salinity in the places where the populations inhabit differs two times. It was shown that the clones of both populations have a broad tolerance and great ability to adapt to changes in salinity. Cells of different size (i.e., in different stages of the life cycle) responded differently to desalination. Salinities optimal for vegetative growth of these species were not the same. Ardissonea from the coast of Martinique was more sensitive to low levels of salinity as compared with A. crystallina from the Black Sea. It was surprising that salinity optimal for vegetative growth and sexual reproduction of the Black Sea species did not coincide with the real salinity level of the Black Sea. Position of physiological optimums indicates an oceanic (or Mediterranean) origin of the Black Sea population of A. crystallina. [ABSTRACT FROM AUTHOR]

This study investigated organic matter (OM) and nutrient removal efficiency of mixed algal species from slaughterhouse wastewater (SWW) by using photo-bioreactor. For this purpose, different dilution multiples of 10, 4, and 2 were applied to the SWW, and pure wastewater was finally used for algal cultivation. OM and nutrient removal performance in an algal photo-bioreactor were severely affected by the dilution ratio. After 7 days of cultivation, the highest removal percentages of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) were 89.6, 70.2, and 96.2 %, respectively. Furthermore, the changes in eukaryotic algae and cyanobacterial species in the algal photo-bioreactors were investigated using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results indicated that cyanobacterial species were more efficient than eukaryotic species in removing nutrients from the SWW. This study suggests that mixed algal photo-bioreactors could be used efficiently in the treatment of SWW. [ABSTRACT FROM AUTHOR]

Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata ( Porphyra haitanensis) is an economically important genus that is cultured widely in China. P. haitanensis is cultured on a larger scale than Pyropia yezoensis, making up an important part of the total production of cultivated Pyropia in China. However, the majority of molecular mechanisms underlying the physiological processes of P. haitanensis remain unknown. P. haitanensis could utilize inorganic carbon and the sporophytes of P. haitanensis might possess a PCK-type C-like carbon-fixation pathway. To identify microRNAs and their probable roles in sporophyte and gametophyte development, we constructed and sequenced small RNA libraries from sporophytes and gametophytes of P. haitanensis. Five microRNAs were identified that shared no sequence homology with known microRNAs. Our results indicated that P. haitanensis might posses a complex sRNA processing system in which the novel microRNAs act as important regulators of the development of different generations of P. haitanensis. [ABSTRACT FROM AUTHOR]

Phaeodactylum tricornutum is a potential livestock for the combined production of eicosapentaenoic acid (EPA) and fucoxanthin. In this study, six marine diatom strains identified as P. tricornutum were cultured and their total lipid, fatty acid composition and major photosynthetic pigments determined. It was found that the cell dry weight concentration and mean growth rate ranged between 0.24-0.36 g/L and 0.31-0.33/d, respectively. Among the strains, SCSIO771 presented the highest total lipid content, followed by SCSIO828, and the prominent fatty acids in all strains were C16:0, C16:1, C18:1, and C20:5 (EPA). Polyunsaturated fatty acids, including C16:2, C18:2, and EPA, comprised a significant proportion of the total fatty acids. EPA was markedly high in all strains, with the highest in SCSIO828 at 25.65% of total fatty acids. Fucoxanthin was the most abundant pigment in all strains, with the highest in SCSIO828 as well, at 5.50 mg/g. The collective results suggested that strain SCSIO828 could be considered a good candidate for the concurrent production of EPA and fucoxanthin. [ABSTRACT FROM AUTHOR]

Compounds isolated and identified in a culture of the alga-endophytic fungus Talaromyces sp. cf-16 included two naturally occurring alkaloids, 2-[( S)-hydroxy(phenyl)methyl]-3-methylquinazolin-4(3H)-one ( 1a) and 2-[( R)-hydroxy(phenyl)methyl]-3-methylquinazolin-4(3H)-one ( 1b), that were identified for the first time. In addition, seven known compounds ( 2- 8) were obtained from the culture. Following chiral column chromatography, compounds 1a and 1b were identified as enantiomers by spectroscopic analyses and quantum chemical calculations. Bioassay results showed that 5 was more toxic to brine shrimp than the other compounds, and that 3- 6 could inhibit Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

Algal allelopathy is a manifold ecological/physiological phenomenon that is focused on chemical interactions and autotoxicity. We investigated the allelopathic interactions between Karenia mikimotoi and Dunaliella salina in laboratory cultures based on diff erent temperature (15°C, 20°C, and 25°C) and lighting (40, 80, and 160 μmol/(m·s)) conditions. The growth of D. salina in bi-algae culture (1:1 size/density) was significantly restrained. The results of cell-free filtrate culture indicate that direct cell-tocell contact was not necessary in interspecific competition. Further experimental results demonstrated that allelochemicals released from K. mikimotoi were markedly influenced by both temperature ( P =0.013) and irradiance ( P =0.003), resulting in diff erent growth characteristics of D. salina in filtrate mediums. Compared with the plateau period, K. mikimotoi exudates in the exponential phase had a stronger short-term inhibition effect on D. salina in normal conditions. A clear concentration-dependent relationship was observed in the effect of allelochemicals released from K. mikimotoi with low-promoting and high-repressing effects on D. Salina in a short time-scale. In addition, allelopathic substances remain stable and effective under high temperature and pressure stress. Many flocculent sediments adhering with D. salina cells were observed in all filtrate mediums, while the quantity and color depended on the original culture conditions. [ABSTRACT FROM AUTHOR]

In order for microalgae-based processes to reach commercial production for biofuels and high-value products such as omega-3 fatty acids, it is necessary that economic feasibility be demonstrated at the industrial scale. Therefore, process optimization is critical to ensure that the maximum yield can be achieved from the most efficient use of resources. This is particularly true for processes involving heterotrophic microalgae, which have not been studied as extensively as phototrophic microalgae. An area that has received significant conceptual praise, but little experimental validation, is that of nutrient recycling, where the waste materials from prior cultures and post-lipid extraction are reused for secondary fermentations. While the concept is very simple and could result in significant economic and environmental benefits, there are some underlying challenges that must be overcome before adoption of nutrient recycling is viable at commercial scale. Even more, adapting nutrient recycling for optimized heterotrophic cultures presents some added challenges that must be identified and addressed that have been largely unexplored to date. These challenges center on carbon and nitrogen recycling and the implications of using waste materials in conjunction with virgin nutrients for secondary cultures. The aim of this review is to provide a foundation for further understanding of nutrient recycling for microalgae cultivation. As such, we outline the current state of technology and practical challenges associated with nutrient recycling for heterotrophic microalgae on an industrial scale and give recommendations for future work. [ABSTRACT FROM AUTHOR]

The quality and regulation of the incident light is crucial in microalgae cultivation processes. Depending on wavelength, spectrum, and intensity, growth characteristics and biochemical composition of these organisms vary. With mainly fluorescent lamps (FL) used previously for illumination, such variabilities could not be studied adequately due to their broad emission spectrum. In contrast, light-emitting diodes (LEDs) emit a very narrow wavelength band and enable flexible photobioreactor designs due to their small size. This review provides a condensed overview on the application of LEDs in microalgal cultivation processes. It summarizes the current availability and applicability of LED technologies as an illumination source for research-focused photobioreactor systems. A particular focus is the use of narrow-wavelength LEDs to address fundamental as well as applied aspects of light color on algae biomass and value-added compound formation. In this respect, the application of internal and external illumination systems is reviewed together with trends in the industrial use of LED systems to intensify algae process efficiency. [ABSTRACT FROM AUTHOR]

Microalgae cultivation has gained much interest in terms of the production of foods, biofuels, and bioactive compounds and offers a great potential option for cleaning the environment through CO sequestration and wastewater treatment. Although open pond cultivation is most affordable option, there tends to be insufficient control on growth conditions and the risk of contamination. In contrast, while providing minimal risk of contamination, closed photobioreactors offer better control on culture conditions, such as: CO supply, water supply, optimal temperatures, efficient exposure to light, culture density, pH levels, and mixing rates. For a large scale production of biomass, efficient photobioreactors are required. This review paper describes general design considerations pertaining to photobioreactor systems, in order to cultivate microalgae for biomass production. It also discusses the current challenges in designing of photobioreactors for the production of low-cost biomass. [ABSTRACT FROM AUTHOR]

Biofilm-based algal cultivation has received increased attention as a potential platform for algal production and other applications such as wastewater treatment. Algal biofilm cultivation systems represent an alternative to the suspension-based systems that have yet to become economically viable. One major advantage of algal biofilm systems is that algae can be simply harvested through scraping and thus avoid the expensive harvesting procedures used in suspension-based harvesting such as flocculation and centrifugation. In recent years, an assortment of algal biofilm systems have been developed with various design configurations and biomass production capacities. This review summarizes the state of the art of different algal biofilm systems in terms of their design and operation. Perspectives for future research needs are also discussed to provide guidance for further development of these unique cultivation systems. [ABSTRACT FROM AUTHOR]

Eighteen microalgae, including two local isolates, were evaluated for their ability to grow and remove nutrients from unsterilized primary or secondary wastewater effluents as well as wastewater supplemented with nutrient-rich anaerobic digester centrate (ADC). Most of the tested species except several phylogenetically clustered Chlorella sorokiniana including local isolates and Scenedesmus strains were unable to grow efficiently. This may reflect the presence of certain genetic traits important for robust growth in the unsterilized wastewater. The maximum algal-specific growth rates and biomass density obtained in these bacterial-contaminated cultures were in the range of 0.8-1 day and 250-350 mg L, respectively. ADC supplementation was especially helpful to biologically treated secondary effluent with its lower initial macronutrient and micronutrient content. As a result of algal growth, total nitrogen and orthophosphate levels were reduced by as much as 90 and 70 %, respectively. Biological assimilation was estimated to be the main mechanism of nitrogen removal in primary and secondary effluents with ammonia volatilization and bacterial nitrification-denitrification contributing for cultures supplemented with ADC. Assimilation by algae served as the principal mechanism of orthophosphate remediation in secondary wastewater cultures, while chemical precipitation appeared also to be important for orthophosphate removal in primary wastewater. Overall, cultivation of microalgae in primary and primary + 5 % ADC may be more favorable from an economical and sustainability perspective due to elimination of the costly and energy-intensive biological treatment step. These findings demonstrate that unsterilized wastewater and ADC can serve as critical nutrient sources for biomass generation and that robust microalgae can be potent players in wastewater phytoremediation. [ABSTRACT FROM AUTHOR]

The biological activity of ethyl acetate extract of exometabolites from the marine microalgae Phaeodactylum tricornutum against a test culture of Listeria monocytogenes 4b has been investigated. It was shown that the stimulating effect of algal exometabolites on the growth of pathogenic bacteria increased maximally by 98.3% on day 6 of the cultivation, if the active substances comprising the culture liquid of P. tricornutum were separated by successive extractions with solvents in order of increasing polarity (hexane, benzene, ethyl acetate), and by 150% on day 3, if the substances from the ethyl acetate extract of exometabolites were separated by column chromatography. It is noted that the fraction of biologically active substances maximally stimulating the growth of L. monocytogenes can be used to prepare an accumulation medium for detecting these pathogenic bacteria in marine environments and hydrobionts. [ABSTRACT FROM AUTHOR]

This study presents a metabolite profile analysis of unicellular green alga Chlamydomonas reinhardtii grown under autotrophic conditions at late stages of culture development. Metabolites were identified by gas chromatography coupled to mass spectrometry. Approximately 400 peaks corresponding to individual compounds were distinguished, of which approximately 100 compounds (including saccharides, fatty acids, aromatic compounds, amino acids, alcohols, etc.) were identified. A local database of mass spectra of unidentified compounds was created using MassBank software. Mapping of the metabolomic data with the use of the ChlamyCyc service showed that the identified compounds are involved in various energetic, synthetic, and signaling pathways in Chlamydomonas. The mapping of metabolites by their chemical structure with the use of Cytoscape software, combined with quantitative interpretation, showed that the majority of organic matter was concentrated primarily in the carbon backbones of fatty acids and terpenes, as well as saccharides and structurally similar compounds. [ABSTRACT FROM AUTHOR]

We present results on the effect of modified clay on cyst formation of Scrippsiella trochoidea in harmful algal bloom (HAB). Modified clay (in concentration of 0, 0.1, 0.5, and 1.0 g/L) were added to cultures, and observations were made on cysts of S. trochoidea under controlled laboratory conditions. Results indicate that the removal rate of algal cells reached 97.7% at the clay concentration of 1.0 g/L. The cyst formation rate increased from 4.6% to 24.6% when the concentration of clay was increased from 0 to 1.0 g/L. Two cyst metamorphs were observed: spinal calcareous cysts and smooth noncalcareous ones. The proportion of the spinal cysts decreased from 76.9% to 24.1% when clay concentration increased from 0 to 1.0 g/L. In addition, modified clay affected cyst germination. The germination rate decreased with the increases in the clay concentrations. Non-calcareous cysts had a lower germination rate with a longer germination time. We conclude that modified clay could depress algal cell multiplication and promote formation of temporal cysts of S. trochoidea, which may help in controlling HAB outbreaks. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) individually and mixed at equal proportions (1:1:1) on Desmodesmus subspicatus and Pseudokirchneriella subcapitata in single and combined cultures (S+) at different exposure times based on algal growth (in vivo chlorophyll fluorescence and cell counting) and coenobium formation. EE2 and E2 were more toxic to individual and combined (S+) cultures than was E1. The frequency of coenobium formation by D. subspicatus increased significantly for all estrogens and all concentrations. After 96 h, D. subspicatus prevailed in S+. The results of the exposure to E+ suggested a less-than-additive effect on D. subspicatus and S+ and additive effect on P. subcapitata. Toxic effects occurred for both species exposed to E+ with individual estrogen concentrations below the NOEC of each species. Assays must include changes in response due to the exposure of more than one species to more than one estrogen. [ABSTRACT FROM AUTHOR]

Inducing lipid accumulation in microalgae cells without suppressing cell growth is vital to the economical production of biodiesel from microalgae. In two experiments, we demonstrate that the cell concentration and lipid content of marine microalgae Isochrysis galbana depend upon the iron concentration in the growth media. In Experiment I, adding chelated FeCl to the medium at the late exponential growth phase prolonged this phase and increased the lipid content in I. galbana cells. The final cell density and lipid content of I. galbana supplemented with chelated FeCl was approximately 2 and 1.65 times higher than that of non-supplemented cultures, respectively. In Experiment II, I. galbana cells in the late exponential phase were collected and re-inoculated into new media containing Fe at various concentrations. The final cell concentration and lipid content were maximized at the highest iron concentration (38% biomass by dry weight at 1.2×10 mol/L Fe). In this study, intracellular neutral lipid storage was evaluated by fluorescent spectrophotometry using fluorochrome Nile red, and the measurement conditions were optimized. [ABSTRACT FROM AUTHOR]

Physiological characteristics of a novel strain of the halophilic alga Dunaliella salina IPPAS D-232 isolated from the hypersaline lake Razval (Sol-Iletsk, Orenburg region) were studied. It was shown that the extract from the cells of this strain manifested antioxidant properties and also antibacterial activity relative to opportunistic bacteria. The influence of medium stirring and salinity on the level of D. salina antioxidant activity was assessed: it was established that medium salinization (93 g/L) and continuous stirring favored the highest accumulation of D. salina IPPAS D-232 biomass. It was found that the extremely halophilic archaea Halorubrum tebenquichense and moderately halophilic bacterium Marinococcus halophilus stimulated D. salina development and increased its antioxidant activity. The results obtained expand our knowledge of specific ecological features of the studied microalgal species; they could form the basis for the development of new approaches to the mass cultivation of D. salina. [ABSTRACT FROM AUTHOR]

The fluid dynamic environment within a photobioreactor is critical for performance as it controls mass transfer of photosynthetic gases (CO and O) and the mixing environment of the algal culture. At a cellular level, light fluctuation will occur when cells move between the 'light', well-illuminated volume of the culture near the light source and the 'dark', self-shaded zone of the culture. Controlled light/dark frequency may increase the light to biomass yield and prevent photoinhibition. Knowledge of cell trajectories within the reactor is therefore important to optimize culture performance. This study examines the cell trajectories and light/dark frequencies in a stratified gas-liquid flow tubular photobioreactor. Commercially available computational fluid dynamics software, ANSYS Fluent, was used to investigate cell trajectories within the half-full solar receivers at different liquid velocities and reactor tube diameters. In the standard configuration 96-mm solar receiver tube, the light/dark cycle frequencies ranged from 0.104 to 0.612 Hz over the liquid velocity range of 0.1 to 1 m s. In comparison, the smaller diameter 48- and 24-mm tubes exhibit higher light/dark frequencies, 0.219 to 1.30 Hz and 0.486 to 2.67 Hz, respectively. [ABSTRACT FROM AUTHOR]

An annular internally illuminated photobioreatcor (IIPBR) configuration based on the airlift/bubble column principles was developed and validated at an 18 l prototype scale using Scenedemus sp . and Nannochloropsis salina in batch and semi-continuous modes, at constant light supply and constant gas-to-culture volume ratio, but at varying CO-to-air ratios. Highest biomass production was recorded at CO-to-air ratio of 4% with Scenedesmus sp. and at 1% with Nannochloropsis salina. The energetic performance of this IIPBR was quantified in terms of biomass productivity per unit energy input, P/E (g W day), considering energy input for illumination and for pneumatic mixing and circulation. Under optimal conditions, the IIPBR evaluated in this study achieved P/E of 1.42 g W day for Scenedesmus sp. and P/E of 0.34 g W day for Nannochloropsis salina. These P/E values are better than those estimated for airlift and bubble column photobioreactor configurations reported in the literature. [ABSTRACT FROM AUTHOR]

Kappaphycus alvarezii was cultured in vitro under salinities ranging from 15 to 55 psu for 35 days to determine the differential effect on growth rate, carrageenan yield, and cellular structure. Plants kept in 15 psu died after 3 days, while plants cultured in 55 psu presented low growth rates during the entire experimental period (0.28% day). Plants cultured in 25, 35, and 45 psu showed growth rates normally associated with this species (between 3% and 4% day) and similar cellular morphology. Carrageenan yield was significantly higher in plants cultured in 25 psu in relation to the other treatments. As observed by light microscopy, plants cultured in 15 psu showed cellular turgidity and increased cell wall thickness, both consequences of hyposalinity. Chloroplasts and other membranous organelles underwent rupture and considerable disorganization in ultrastructure. Although branches from the 55 psu samples showed plasmolysis, cells were able to maintain chloroplast integrity, despite their rudimentary features. In high salinities, great concentrations of floridean starch grains were observed in subcortical cells, indicating their probable participation in osmoregulation. Based on these results, we defined the range of 25 to 45 psu as the limits of saline tolerance for K. alvarezii. While new field studies are required to confirm these results, it can be concluded that new sites, such as inactive or abandoned shrimp tanks with salinities up to 25 psu, could be considered for commercial farming. [ABSTRACT FROM AUTHOR]

Undariopsis peterseniana is an endangered annual brown alga in Udo, Jeju Island, Korea. There is current interest in the commercial-scale aquaculture of this species for warm-water species development in Korea. Growth and maturation were investigated from January to December 2007 in their natural habitat. Zoospores were transplanted into an intensive seaweed culture ground in Wando, southern coast of Korea, for the mass cultivation of this species. Indoor and outdoor cultivation were conducted from June 2007 to May 2008. Mean production obtained from the zoospore seeding was 31.1 ± 1.5 kg wet wt. m of culture rope during the cultivation period in situ. Transplanted F thalli in Wando had a length 1.7 times longer than their parents in Udo, and their maximal growth period changed from June (at 19.9°C in Udo of natural habitat) to April (at 14.0°C in Wando of culture ground). The relationship between optimal water depth for culture and underwater irradiance during the U. peterseniana cultivation was defined as: $$ y = - 0.78 \times + 7.67\left( {{r^2} = 0.92} \right) $$. This study indicates that U. peterseniana could be successfully transferred to the northern coast beyond the original habitat in Jeju Island. [ABSTRACT FROM AUTHOR]

newly proposed three-dimensional model for the effects of heavy metals on the growth of batch cultures of algae that allows the estimation of the no detected toxic effect concentration (NDEC) is presented. Two batch assays with exposure to copper were investigated in situ (ship-based enclosure). As an endpoint in these studies, the carrying capacity B, a parameter of the logistic growth model, possesses higher sensitivity and reliability than routine ecotoxicological endpoints. Using B as the endpoint, the NDEC from the proposed model is compared to the no observed effect concentration (NOEC), Lowest Observed Effect Concentration (LOEC), the 5% effect concentration (EC) and no effect concentration (NEC) also calculated from field-derived data. The results show the confidence interval for the NDEC was wholly contained within the corresponding interval between the NOEC and LOEC, as well as within the corresponding much wider confidence interval for EC. Though the width of the confidence interval for NEC was basically equivalent to the corresponding width for NDEC, the NEC was somewhat higher than the corresponding NDEC. The results indicate that the NDEC is a promising possible alternative parameter to the NOEC. [ABSTRACT FROM AUTHOR]

The influence of pH shift and NaCl salting on the heat production, oxygen adsorption, and oxygen evolution rates of the unicellular green halotolerant microalga Dunaliella maritima and the freshwater microalga Chlorella vulgaris were investigated . In the growth process of both microalgae the alkalization of their culture medium was observed. And simultaneously it was shown that at increasing NaCl salting of cultural medium its acidification occurs. At alkalization and acidification of Chlorella medium the increase of heat production and respiration rates were observed. At alkalization and acidification of Dunaliella culture the adverse effect of decreasing heat production rate was observed. Acidification of culture medium of both algae led to short-term and sharp increase of photosynthesis measured by polarography and photomicrocalorimeter. [ABSTRACT FROM AUTHOR]

In order to enhance microalgal growth in photobioreactors (PBRs), light requirement is one of the most important parameters to be addressed; light should indeed be provided at the appropriate intensity, duration, and wavelength. Excessive intensity may lead to photo-oxidation and -inhibition, whereas low light levels will become growth-limiting. The constraint of light saturation may be overcome via either of two approaches: increasing photosynthetic efficiency by genetic engineering, aimed at changing the chlorophyll antenna size; or increasing flux tolerance, via tailoring the photonic spectrum, coupled with its intensity and temporal characteristics. These approaches will allow an increased control over the illumination features, leading to maximization of microalgal biomass and metabolite productivity. This minireview briefly introduces the nature of light, and describes its harvesting and transformation by microalgae, as well as its metabolic effects under excessively low or high supply. Optimization of the photosynthetic efficiency is discussed under the two approaches referred to above; the selection of light sources, coupled with recent improvements in light handling by PBRs, are chronologically reviewed and critically compared. [ABSTRACT FROM AUTHOR]

Quantitative phytochelatin (PC) analysis is, due to oxidation sensitivity of the PCs, matrix effects, and time consuming sample preparation, still a challenging analytical task. In this study, a rapid, simple, and sensitive method for precise determination of native PCs in crude extracts of the green alga Chlamydomonas reinhardtii was developed. Algae were exposed 48 h to 70 μM Cd. Coupling of ultra performance liquid chromatography and electrospray ionization tandem mass spectrometry with multi-reaction mode transitions for detection permitted the required short-time, high-resolution separation and detection specificity. Thus, under optimized chromatographic conditions, 10 thiol peptides were baseline-separated within 7 min. Relative detection limits in the nanomolar range in microliter sample volumes were achieved (corresponding to absolute detection limits at femtomol level). Next to glutathione (GSH), the most abundant cadmium-induced PCs in C. reinhardtii, namely CysGSH, PC, PC, CysPC, and CysPC, were quantified with high reproducibility at concentrations between 15 and 198 nmol g fresh weight. The biological variation of PC synthesis of nine independently grown alga cultures was determined to be on average 13.7%. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Sewage sludge applied to soils as a fertilizer often contains metals and linear alkylbenzene sulphonate (LAS) as contaminants. These pollutants can be transported to the aquatic environment where they can alter the phosphatase activity in living organisms. The acid phosphatase of algae plays important roles in metabolism such as decomposing organic phosphate into free phosphate and autophagic digestive processes. The order of in vitro inhibition of Pseudokirchneriella subcapitata acid phosphatase at the highest concentration tested was LAS > Hg2+ = Al3+ > Se4+ = Pb2+ > Cd2+. A non-competitive inhibition mechanism was obtained for Hg2+ (Ki = 0.040 mM) and a competitive inhibition for LAS (Ki = 0.007 mM). In vivo studies with treated algae cultures showed that the inhibition of specific activity was observed in algae exposed during 7 days, in contrast to short term (24 h) treatments with both these chemicals. Our results suggest that the inhibition parameters in vitro did not markedly differ between the two chemicals. On the other hand, in vivo evaluations showed strong differences between both pollutants regarding the concentration values and the degree of response. [ABSTRACT FROM AUTHOR]

We investigated the growth interaction between Cochlodinium polykrikoides and Akashiwo sanguinea using bi-algal cultures. When cultured together, morphologically abnormal cells of A. sanguinea appeared and the growth of A. sanguinea notably decreased. When C. polykrikoides and A. sanguinea were cultured separately in inner and outer wells separated by a membrane with a pore size of 3 μm, neither species showed suppressed growth and no morphologically abnormal cells of A. sanguinea were observed. Furthermore, filtrates from C. polykrikoides cultures did not affect the cell morphology or the growth of A. sanguinea. When the abnormal cells of A. sanguinea were transferred from bi-algal cultures into fresh medium and cultured as a mono-algal culture, cells recovered their normal morphology and multiplied. Therefore, the growth inhibition and formation of morphologically abnormal cells of A. sanguinea would be induced by constant cell contact with C. polykrikoides. [ABSTRACT FROM AUTHOR]

Abstract??The tissue culture of phycocolloid yielding seaweeds included preparation of axenic explants, callus induction, subculture of excised callus and regeneration of plantlets from pigmented callus in the laboratory. Treatment of algal material with 0.1?0.5% detergent for 10 min and 1?2% betadine for 1?5 min and 3?5% antibiotic treatment for 48?72 h successively enabled viable axenic explants to be obtained as high as 60% forGracilariacorticata,SargassumtenerrimumandTurbinariaconoidesand 10% forHypneamusciformis. Callus induction was more conspicuous inT.conoidesthan in the other three species investigated. Of the irradiances investigated, 30 ?mol photons m?2s?1produced calluses in as many as 40% explants inG.corticataandT.conoidesand 10% inH.musciformisandS.tenerrimum. The explants cultured at 5 and 70 ?mol photons m?2s?1did not produce any callus in all the species studied except forH.musciformisin which 10% explants developed callus at 5 ?mol photons m?2s?1. Most of the species investigated showed uniseriate filamentous Type of growths and buds from cut ends and from all over the surface of explants. Nevertheless,T.conoideshad three Types of callus developments, namely (1) uniseriate filamentous Type of outgrowths from the centre of the cut end of explant, (2) bubbly Type of callus and (3) club-shaped callus clumps. The subculture ofT.conoidescallus embedded in 0.4% agar produced two Types of filamentous growth, namely filiform (with elongated cells) and moniliform filaments (with round cells) in the 2 months period after inoculation. Further, friable callus with loose cells was also found associated with excised callus. The moniliform filaments showed prolific growth of micro-colonies resembling to somatic embryo-like growth which, in liquid cultures, differentiated and developed into propagules with deformed shoots and distinct rhizoids. The shoots of these propagules remained stunted with abnormal leaf stalks without forming triangular shaped leaves as the parental plant and rhizoids had prolific growth in the laboratory cultures. The excised callus ofG. corticatacontinued to grow when transferred to liquid cultures and showed differentiation of new shoots within 10 days. The shoots grew to a maximum length of 5?6 cm in the 2 months period in aerated cultures in the laboratory. [ABSTRACT FROM AUTHOR]

Abstract??During the last two decades, the monostromatic green seaweedGayraliasp. has been harvested sporadically by local fishermen on the Paran? coast of southern Brazil and sold to Japanese restaurants. However, the production is erratic and its economic impact very small. This paper provides basic information about a technique to cultivate this seaweed on suspended nets in Paranagu? Bay, southern Brazil, aiming to develop a more reliable and sustainable source of income for impoverished coastal dwellers.Gayraliasp. occurs year round in the region, usually growing on mangrove stems and roots. Polypropylene nets (10?m long ? 1?m wide with 16?cm mesh) were placed close to the mangrove fringe. Recruitment occurred year round reaching a peak of 500 recruits m?2during early spring. Higher recruitment occurred at periods of low temperature (21?23?C) and high salinity (30?33 psu). Growth rates ofGayraliasp. ranged from 5.75 ? 0.56% to 6.50 ? 0.43% day?1during the winter and from 1.43 ? 1.65% to 4.65 ? 2.17% day?1, during the summer. Production ranged from 22 ? 6?g m?2DW in June to 58 ? 21?g m?2DW in September 2004 in 45 days after zooid settlement. The simplicity of the cultivation method, reasonable growth rates and extensive favorable area for cultivation suggest that mariculture ofGayraliasp. may become a good alternative of income for the local inhabitants. [ABSTRACT FROM AUTHOR]