Showing papers in "Journal of Applied Phycology in 1999"
TL;DR: The data for worldwide seaweed production for the years 1994/1995 are summarised, with the value of the harvest in excess of US $ 6.2 billion.
Abstract: The data for worldwide seaweed production for the years 1994/1995 are summarised At least 221 species of seaweed were used, with145 species for food and 101 species for phycocolloid production 2,005,459 t dry weight was produced, with 90% coming from China, France, UK, Korea, Japan and Chile 1,033,650 t dry weight was cultured with 90% coming from China, Korea and Japan Just four genera made up 93% of the cultured seaweed: Laminaria (682,581 t dry wt), Porphyra (130,614 t dry wt), Undaria (101,708 t dry wt) and Gracilaria (50,165 t dry wt) The value of the harvest was in excess of US $ 62 billion Since 1984 the production of seaweeds worldwide has grown by 119%
343 citations
TL;DR: In this paper, a method of nitrate determination by ultraviolet absorption spectrometry is proposed based on the measurement of sample absorbance at a single wavelength (220 nm), which was chosen on the basis of the absorption spectra of the main components of artificial seawater in the ultraviolet domain No reagents are used and no sophisticated instruments are necessary.
Abstract: This method of nitrate determination by ultraviolet absorption spectrometry is based on the measurement of sample absorbance at a single wavelength (220 nm), which was chosen on the basis of the absorption spectra of the main components of artificial seawater in the ultraviolet domain No reagents are used and no sophisticated instruments are necessary For standards prepared in artificial seawater, the relationship between absorbance and nitrate concentration is linear up to 500 μmol N L−1 and the detection limit is 1 μmol N L−1 Precision is 15% Urea and amino acids did not interfere at concentrations typical of seawater The method also measures nitrite, but this interference only becomes important for species which excrete large amounts of nitrite The method is extremely rapid, simple to implement and does not require the use of toxic chemicals such as cadmium It should prove useful for monitoring quickly the nitrate concentrations in laboratory cultures of marine phytoplankton
238 citations
TL;DR: It is concluded that such techniques, based on ecological engineering, seems promising for mitigating environmental impacts from intensive mariculture; however, continued research on this type of solution is required.
Abstract: Rapid scale growth of intensive mariculture systems can often lead to adverse impacts on the environment. Intensive fish and shrimp farming, being defined as throughput-based systems, have a continuous or pulse release of nutrients that adds to coastal eutrophication. As an alternative treatment solution, seaweeds can be used to clean the dissolved part of this effluent. Two examples of successfully using seaweeds as biofilters in intensive mariculture systems are discussed in this paper. The first example shows that Gracilaria co-cultivated with salmon in a tank system reached production rates as high as 48.9 kg m−2 a−1, and could remove 50% of the dissolved ammonium released by the fish in winter, increasing to 90–95% in spring. In the second example, Gracilaria cultivated on ropes near a 22-t fish cage farm, had up to 40% higher growth rate (specific growth rate of 7% d−1) compared to controls. Extrapolation of the results showed that a 1 ha Gracilaria culture gave an annual harvest of 34 t (d. wt), and assimilated 6.5% of the released dissolved nitrogen. This production and assimilation was more than twice that of a Gracilaria monoculture. By integrating seaweeds with fish farming the nutrient assimilating capacity of an area increases. With increased carrying capacity it will be possible to increase salmon cage densities before risking negative environmental effects like eutrophication and toxic algal blooms sometimes associated with the release of dissolved nutrients. The potential for using mangroves and/or seaweeds as filters for wastes from intensive shrimp pond farming is also discussed. It is concluded that such techniques, based on ecological engineering, seems promising for mitigating environmental impacts from intensive mariculture; however, continued research on this type of solution is required.
215 citations
TL;DR: Comparison of the data with the known nutritional requirements for marine fish species and prawns suggests that the microalgae should provide excess or adequate levels of the vitamins for aquaculture food chains.
Abstract: The vitamin content in four Australian microalgae, a Nannochloropsis-like sp., Pavlova pinguis, Stichococcus sp. and Tetraselmis sp., were examined. These were grown under a 12:12 h light:dark regimen (100 μmol photon m−2s−1) and harvested during late-logarithmic phase. Typically, the content showed a two- to three fold range between the species. When expressed on a dry weight basis, the content of ascorbate ranged from 1.3 to 3.0 mg g−1, β-carotene from 0.37 to 1.05 mg g−1, α-tocopherol from 0.07 to 0.29 mg g−1, thiamine from 29 to 109 μg g−1, riboflavin from 25 to 50 μg g−1, total folates from 17 to 24 μg g−1, pyridoxine from 3.6 to 17 μg g−1, cobalamin from 1.70 to 1.95 μg g−1 and biotin from 1.1 to 1.9 μg g−1. Retinol was detected only in Tetraselmis sp. (2.2 μg g−1); any vitamins D2 or D3 were below the detection limit (≤0.45 μg g−1). Nannochloropsis sp. was also grown under a 24:0 h light:dark light cycle and harvested at stationary phase. The content of most vitamins in Nannochloropsis sp. cultures differed significantly, and the degree of variation was similar to that observed between the four species grown under 12:12 h light:dark regimen (100 μmol photon m−2s−1) and harvested during late-logarithmic phase. Thiamine content was also examined in six non-Australian strains commonly used in aquaculture, Chaetoceros muelleri, Thalassiosira pseudonana, Nannochloris atomus, Nannochloropsis oculata, Isochrysis sp. (T.ISO) and Pavlova lutheri. Values (average 61 μg g−1; range 40 to 82) were similar to those in the Australian strains (average 61 μg g−1; range 29 to 109) and increased during stationary phase (average 94 μg g−1; 38 to 131). Comparison of the data with the known nutritional requirements for marine fish species and prawns suggests that the microalgae should provide excess or adequate levels of the vitamins for aquaculture food chains. The data may be used to guide the content of vitamins included in micro-diets developed as replacements for live diets.
197 citations
TL;DR: It is reported that UV light exposure, especially in the UV-C range, can stimulate phenolic-antioxidant production in aplanospores of C. nivalis effecting biochemical pathways related to proline metabolism.
Abstract: The snow alga Chlamydomonas nivalis was collected from the Sierra Nevada, California, USA, and examined for its ability to produce phenolic compounds, free proline, and provide antioxidant protection factor in response to UV-A and UV-C light. Exposure of C. nivalis cells to UV-A light (365nm) for 5 days resulted in a 5–12% increase in total phenolics, where as exposure to UV-C light (254 nm) resulted in a 12–24% increase in phenolics after 7 days of exposure. Free proline was not affected by UV-A, but increased markedly after UV-C exposure. A three-fold increase in free proline occurred within two days after exposure to UV-C, but then dropped as cells became bleached. Antioxidant protection factor (PF) increased after treatment of cells with UV-A and remained constant throughout UV-C exposure. Spectral analysis of algal extracts revealed a decrease in absorption in the 215–225 nm region, short-term (2day) stimulation of pigment at 280 nm, and an increase in carotenoids (473 nm), after exposure to UV-A. Snow alga exposed to UV-C light had a different spectrum from that of UV-A exposed cells, i.e. an enhancement of three major peaks at 220, 260, and 280 nm, and loss of absorption in the carotenoid region.We report that UV light exposure, especially in the UV-C range, can stimulate phenolic-antioxidant production in aplanospores of C. nivalis effecting biochemical pathways related to proline metabolism.
182 citations
TL;DR: To enable the production of conchospores for net seeding, the phenology of these species and the conditions for their vegetative conchocelis exponential growth, conchosporangium induction, and Conchospore maturation were determined.
Abstract: For rapid growth and appropriate pigmentation, Porphyra requires the constant availability of nutrients, especially in summer when temperate waters are generally nutrient depleted. Cultivation near salmon cages allows the alleviation of this seasonal depletion by using the significant loading of fish farms, which is then valued (wastes become fertilisers) and managed (competition for nutrients between desirable algal crops and problem species associated with severe disturbances). Porphyra, being an extremely efficient nutrient pump, is an excellent candidate for integrated aquaculture for bioremediation and economic diversification. Frequent harvesting provides for constant removal of significant quantities of nutrients from coastal waters, and for production of seaweeds of commercial value. The production of P. yezoensis being limited in the Gulf of Maine, an assessment of the potential of seven native north-west Atlantic Porphyra species is presently in progress. To enable the production of conchospores for net seeding, the phenology of these species and the conditions for their vegetative conchocelis exponential growth, conchosporangium induction, and conchospore maturation were determined. The development of integrated aquaculture systems is a positive initiative for optimising the efficiency of aquaculture operations, while maintaining the health of coastal waters.
169 citations
TL;DR: An increasing number of such metabolites is being found to be directed against oxygenic photosynthetic processes, which, in the microbial world, are unique to algae and cyanobacteria.
Abstract: Cyanobacteria produce a large number and variety of bioactive allelochemical substances, with a diverse range of biological activities and chemical structures, and with effects on many biochemical processes within cells. An increasing number of such metabolites is being found to be directed against oxygenic photosynthetic processes, which, in the microbial world, are unique to algae and cyanobacteria. Such chemicals are likely to be involved in regulating natural populations, and are potentially useful as biochemical tools, and as herbicidal or biocontrol agents.
138 citations
TL;DR: Structural and functional changes of marine benthic vegetation typical of eutrophic waters, in particular mass development (blooms) of certain seaweeds, are not merely the result of increased nutrient loading, but must be attributed to complex interactions of primary and secondary effects during the eutrophication process.
Abstract: Seaweed responses to eutrophication and their role in coastal eutrophication processes were compared at 8 different sites along the European coasts from the Baltic to the Mediterranean as part of the EU-ENVIRONMENT Project Marine Eutrophication and benthic Macrophytes (EUMAC). Structural and functional changes of marine benthic vegetation typical of eutrophic waters, in particular mass development (blooms) of certain seaweeds, are not merely the result of increased nutrient loading, but must be attributed to complex interactions of primary and secondary effects during the eutrophication process. Due to species-specific physiological properties of the algae (nutrient kinetics, growth potential, light, temperature requirements), the combined effects of abiotic and biotic factors on juvenile or adult developmental stages control the development of algal blooms in different ways. In particular the role of light, temperature, water motion and oxygen depletion, as well as of grazers, on early and adult developmental stages of the algae are considered. The result are discussed in the context of coastal eutrophication control and management.
136 citations
TL;DR: The use of enzymes degrading the cell wall polysaccharides as an alternative method to improve the extraction and the solubilization of algal proteins is discussed.
Abstract: With protein contents higher than 20% (dry weight), some red or green seaweeds are potential sources of commercially useful plant proteins. However, the presence of anionic or neutral polysaccharides in large quantities in the cell wall strongly hinders the solubilization of proteins during the application of classical extraction procedures. A present this limits the study and industrial use of seaweed proteins. This short paper is a discussion about the use of enzymes degrading the cell wall polysaccharides as an alternative method to improve the extraction and the solubilization of algal proteins.
118 citations
TL;DR: In this paper, photosynthesis and cell composition of Porphyraleucosticta discs grown at low (< 00001% in air), current (control) and high (1% CO2 in air)inorganic carbon (Ci) concentrations were analyzed.
Abstract: Photosynthesis and cell composition of Porphyraleucosticta discs grown at low (< 00001% in air), current (control) and high (1% CO2 in air)inorganic carbon (Ci) concentrations were analyzed Carbohydrate content in discs grown at high Ci increased (151 mg g-1 FW) with respect to the control (64 mg g FW-1), whereas soluble protein content decreased to one-third (56 to21 mg g-1 FW) Carbohydrate content was unaffected and soluble protein slightly increased in discs grown at low Ci As a consequence of these changes, a lower C/N molar ratio (86) was found in the discs grown at low compared to high Ci(124) Nitrate reductase activity increased at high Ci from 03 ± 02 to 17 ± 04 μmolNO2
- g-1 FW h-1indicating that reduction and assimilation of nitrate were uncoupled The response of photosynthesis to increasing irradiance, estimated from O2evolution vs irradiance curves, was affected by the treatments Maximum quantum yield (Φ O2°) and effective quantum yield (Φ O2) at 150 μmol photon m-2s-1 decreased by 20% and 50%, respectively, at low Ci These differences could be due to changes in photosynthetic electron flow between PSII and PSI Treatments also produced changes in maximal (Fv/Fm) and effective (ΔF/Fm′)quantum yield for photosystem II charge separation
113 citations
TL;DR: It is concluded that P. linearisuses primarily CO2 with HCO3- being an alternative source of Ci for photosynthesis, and its fast growth could be related to the enzyme carbonic anhydrase whose activity was detected intra- and extracellularly.
Abstract: Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were determined for Porphyralinearis grown in 05 L glass cylinders in the laboratory, or in 40 L fibreglass outdoor tanks with running seawater While net photosynthetic rates were uniform at pH 60–80, dropping only at pH 87, growth rates were significantly affected by pH levels other than that of seawater (c pH 83) In glass cylinders, weekly growth rates averaged 76% at external pH 80, 13% at pH 87 and 26% at pH 70 Photosynthetic O2 evolution on a daily basis(ie total O2 evolved during day time less total O2 consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark respiration rates measured at acidic pH Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with regular air (360 mg L-1 CO2) and 28% in algae grown in tanks aerated with CO2-enriched air (750 mg L-1 CO2) The pH of the seawater medium in which P linear is was grown increased slightly during the day and only rarely reached 90 The pH at the boundary layer of algae submerged in seawater increased in response to light reaching, about pH 89 within minutes, or remained unchanged for algae submerged in a CO2-free artificial sea water medium Photosynthesis of P linearissaturated at Ci concentrations of seawater (K05560 μM at pH 82) and showed low photosynthetic affinity for CO2(K05 61 μM) at pH 60 It is therefore concluded that P linearisuses primarily CO2 with HCO3- being an alternative source of Ci for photosynthesis Its fast growth could be related to the enzyme carbonic anhydrase whose activity was detected intra- and extracellularly
TL;DR: The oleic acid (18:1) content maintained a positive and significant correlation with the carotene content per cell and with the irradiance, and may be the main determinant of this correlation.
Abstract: The variation of the fatty acid profile and the carotene content of Dunaliella salina in response to irradiance (80, 128, 640, 1000, 1500 μmol photon m−2 s−1) and nitrogen starvation were analysed. The highest fatty acid content per cell and the least polyunsaturated fatty acid percentage were exhibited under 1500 μmol photon m−2 s−1. Furthermore, the oleic acid (18:1) content maintained a positive and significant correlation with the carotene content per cell and with the irradiance. The composition of the carotene globules in Dunaliella salina may be the main determinant of this correlation.
TL;DR: In this article, a long-term research program on the effect of copper contamination on biota in Chilean coastal waters was presented, and the results indicated that the current low algal diversity and abundance is strongly influenced by herbivory, although chronic effects of the discharges cannot be ruled out.
Abstract: Results are presented of a long-term research programme on the effect of copper contamination on biota in Chilean coastal waters In spite of the magnitude of the copper mining tailings that affected Caleta Palito and surroundings in northern Chile, the effects on the intertidal assemblages remain restricted to a small geographic area Even within the affected area, the effects are not homogeneous and there is evidence of active recovery in biological diversity in recent few years Experimental evidence suggests that the current low algal diversity and abundance is strongly influenced by herbivory, although chronic effects of the discharges cannot be ruled out Cellular changes in Enteromorpha compressa from the impacted area were characterised by abnormal granules in the cytoplasm, though these granules did not contain detectable levels of copper or other heavy metals
TL;DR: The yields attained in this study rank among the highest reported for any intensively managed photosynthetic crop and demonstrate the feasibility of growing red macroalgae like Gracilaria at a sustained high yield in a large-scale, land-based culture system.
Abstract: Gracilaria ferox J. Agardh was grown continuously in large, outdoor tanks under a pulse-fed nutrient regime for four years. Productivity ranged from 21.4 to 59.2 g d. wt m−2 d−1 with a mean of 39.7 g d. wt m−2 d−1 over the entire study period. Because the cultures were maintained under non-nutrient limiting conditions, productivity was regulated primarily by seasonal changes in light and temperature, which accounted for 75% of the variability of growth in algal yields. Salinity ranged from 31.0 to 36.5‰ and had insignificant effects on growth within this range. The original vegetative strain was maintained over the entire study without the need for additional supplementation from field-collected stock. Because of the pulse-fed nutrient supply, epiphytic growth on the target species was negligible (< 3% total biomass) throughout the study. The yields attained in this study rank among the highest reported for any intensively managed photosynthetic crop and demonstrate the feasibility of growing red macroalgae like Gracilaria at a sustained high yield in a large-scale, land-based culture system.
TL;DR: It is concluded that the technology for reducing LHP content is a useful method for improving photosynthetic productivity in algal mass production by reducing the light harvesting pigment content in high cell density cultures at high light intensities.
Abstract: Microalgal productivity was examined using both a wild type and a phycocyanin-deficient mutant of Synechocystis PCC 6714 (PD-1). The culture was conducted at various light intensities under low and high cell densities in a continuous culture system. At low light intensity, photosynthetic productivity was almost the same for both low and high cell densities. However, at higher light intensities photosynthetic productivity was higher in mutant PD-1 than in the wild type. At 2000 μmol photon m−2 s−1 the productivity was 50% higher in mutant PD-1. This result is consistent with our first report (Nakajima & Ueda, 1997), which showed that photosynthetic productivity can be improved by reducing the light harvesting pigment content in high cell density cultures at high light intensities. It is concluded that the technology for reducing LHP content is a useful method for improving photosynthetic productivity in algal mass production.
TL;DR: Phylogenetic trees based on division in complete 18S rDNA sequence data show a deep division in the genus Porphyra that is not obviously correlated with existing morphological characters, and indicate that representatives of the New Zealand flora have undergone long reproductive isolation.
Abstract: The long geographic isolation of New Zealand, an archipelago with a large latitudinal range (29°to 54°S) and an extensive coastline, has resulted in a high level of endemism in both land and coastal marine flora. The genus Porphyra in NZ is represented by 5 epiphytic species and a number of epilithic species, many of which are undescribed. Systematic studies aimed at understanding variation inmorphology and life history are underway, and have led to the description of a number of new species. The present study uses sequence data from the18S rDNA locus to investigate genetic variation in New Zealand Porphyra. Sequences have been fully determined for 10 epilithic species. A subset of these data has been shown to be sufficient to distinguish established taxa and to identify new entities. Our data indicate that New Zealand harbours at least 12 epilithic species of Porphyra, establishing the NZ coastline as a repository of diversity for this genus. Phylogenetic trees based on division in complete 18S rDNA sequence data show a deep division in the genus that is not obviously correlated with existing morphological characters, and indicate that representatives of the New Zealand flora have undergone long reproductive isolation.
TL;DR: Quantitatively different relationships of magnitude and position of spectral reflectance features with chlorophyll- a concentration reflect different optical properties of algae (their scattering and absorption) may be useful for taxonomic characterization by remote sensing.
Abstract: A comparative study was conducted with representatives of four ecologically important freshwater algal phyla (Chlorophyta, Cyanophyta, Bacillariophyta and Pyrrophyta) in order to (1) analyze the relationship between reflectance spectral features and algal density, and (2) to elucidate and characterize possible diagnostic spectral reflectance features for identification of dominant groups in algal bloom states. Algae (two chlorophytes, a cyanophyte and a bacillariophyte) were cultured in mesocosm tanks and then their densities were reduced through dilution with clear water in four experiments. In a fifth experiment, use was made of the pyrrophyte Peridinium gatunense, which bloomed in Lake Kinneret, Israel, practically forming a unialgal ‘culture’. The basic quantitative procedures for spectroradiometeric measurements and support data collection (pigment concentrations) were consistent among the experiments. Several spectral reflectance characteristics were found to be common to all the species examined in the study: a depression between 440 and 500 nm, a salient trough around 670 nm, and prominent peaks centered around 570 nm and 700 nm. The increase in magnitude of a near infra-red peak and shift of its position towards longer wavelengths with increased chlorophyll- a concentration was found to be a common trait for all the species studied. Other specific spectral reflectance features were also found and are discussed here. Quantitatively different relationships of magnitude and position of spectral reflectance features with chlorophyll- a concentration reflect different optical properties of algae (their scattering and absorption). This may be useful for taxonomic characterization by remote sensing.
TL;DR: The results emphasise the potential of the tetraspore progeny for strain selection in K. alvarezii and suggest that the tetrasporophyte used in these studies is of hybrid origin.
Abstract: A brown strain of Kappaphycus alvarezii from the Philippines produced tetraspores in the summer and autumn (December 1995 to May 1996) in cultivation experiments in the sea at Ubatuba, Sao Paulo State, Brazil. In vitro tetraspore release and germination experiments showed a mass mortality two to four days after release. Only 20 plants derived from tetraspores were grown successfully for over a year in the laboratory. Large differences in morphology, colour, size and growth rates were observed amongst these plants. The individual plants differed from one another in one or more characteristic. Differences appeared in the early developmental stages and persisted through time. After ten months, the plants that grew best in laboratory culture were transferred into the sea, but the others remained very small (3 to 5 mm), even after two years. In the sea, the plants also showed individual differences in their ability to survive and grow. These results emphasise the potential of the tetraspore progeny for strain selection in K. alvarezii. The results also suggest that the tetrasporophyte used in these studies is of hybrid origin.
TL;DR: An examination of the specific terms used to describe reproduction and life history in the red algal genus Porphyra is undertaken, it is recommended that the terms carpospore and carposporangium are no longer used for this genus.
Abstract: An examination of the specific terms used to describe reproduction and life history in the red algal genus Porphyra is undertaken to clarify the subject. It is recommended that the terms carpospore and carposporangium are no longer used for this genus. The term phyllospore is proposed for spores produced in spore packets by the blade phase, unless the ploidy or subsequent development of the spores is known, in which case, the terms zygotospore, agamospore or neutral spore can be applied. It is recommended that the terms spermatia and spermatangia are used for male reproductive structures. Archeospores, endospores, protothalli, conchospores and neutral conchospores are also defined.
TL;DR: Basic issues involved in effective use of a high photon irradiance for mass production of microalgae are elucidated: efficient utilisation of high irradiance requires cultures of high cell density grown in reactors with a narrow light path.
Abstract: Basic issues involved in effective use of a high photon irradiance for mass production of microalgae are elucidated: efficient utilisation of high irradiance requires cultures of high cell density grown in reactors with a narrow light path. The smaller the light-path, the higher the growth rate and the volume output rate (g L−1d−1) of cell mass. Areal productivity (g m−2d−1) may be inversely related to the length of light-path (e.g. Spirulina platensis) or directly related to it, as is the case with Nannochloropsis sp., in which the areal output rate increased with the increase in the light-path and the areal volume (L m−2). Inhibition of cell growth in Nannochloropsis became evident as cell concentration increased above a certain point. Response in cell growth to elevated irradiance was therefore possible only when the growth medium of ultrahigh cell density cultures was frequently changed. Inhibitory activity to culture growth may be directly involved in determining the optimal cell density (which results in the highest output of cell mass) and hence the optimal light-path. Under optimal growth conditions, cultures of high cell densities responded well to the rate of stirring, the relative beneficial effect of mixing increasing with the increase in cell density.
TL;DR: The chemical composition and structures of several ulvan extracts isolated from various Ulva species were studied in this article, where they were all composed mainly of rhamnose, glucuronic acid, xylose, glucose and sulphate with smaller amounts of iduronic acids and traces of galactose.
Abstract: The chemical composition and structures of several ulvan extracts isolated from various Ulva species were studied. They were all composed mainly of rhamnose, glucuronic acid, xylose, glucose and sulphate with smaller amounts of iduronic acid and traces of galactose. Proteins were also present, most likely as contaminants. Precise quantification of the uronic acid content by chemical-enzymatic hydrolysis coupled to HPAEC-PAD analysis and by colorimetry was not achieved, most likely due to the incomplete hydrolysis of glucuronan segments, inadequate HPAEC-pulsed-amperometric response factor for iduronic acid and to a possible differential colorimetric response of the two uronic acids. 13C NMR spectroscopic investigation of different ulvans demonstrated that they were all based on ulvanobiuronic acid 3-sulphate A and B repeating units [β-D-Glcp A-(l->4)-α-L-Rhap3S and α- L-IdopA-(l->4)-α-L-Rhap3S, respectively] as well as contiguous β l->4 linked D-glucuronic acids possibly occurring either in ulvan or as a separate glucuronan. Marked variations in the content of the repeating structures were seen among the different samples. However, due to the limited number of samples studied, no conclusion was reached concerning the effects of species and ecophysiological conditions on the chemistry of ulvan.
TL;DR: The results suggest that the decrease in Fv/Fm induced by photoinhibition in outdoor Spirulina cultures was a result of the inactivation of PSII reaction centers and also suggests that the measurement of polyphasic fluorescence transients is a powerful tool to study the mechanism of photoin inhibition.
Abstract: Photoinhibition in outdoor cultures of Spirulina platensis was studied by measuring the polyphasic rise of chlorophyll fluorescence transients, which provide information on the primary photochemistry of PSII. The maximum efficiency of PSII photochemustry (Fv/Fm) declined in response to daily increasing irradiance and recovered as daily irradiance decreased. The greatest inhibition (15%) in Fv/Fm was observed at 12:00 hr which responded to the highest irradiance. The absorption flux, the trapping flux, and the electron transport flux per PSII reaction center increased in response to daily increasing irradiance and decreased as irradiance decreased. The daily change in the concentration of PSII reaction centers followed the same pattern as Fv/Fm. However, no significant changes in the probability of electron transport beyond QA (Ψo) were observed during the day. The results suggest that the decrease in Fv/Fm induced by photoinhibition in outdoor Spirulina cultures was a result of the inactivation of PSII reaction centers. The results also suggest that the measurement of polyphasic fluorescence transients is a powerful tool to study the mechanism of photoinhibition in outdoor Spirulina cultures and to screen strains for photoinhibition tolerance.
TL;DR: In this article, the effect of temperature (70, 80, 90C) and time (1−9 h) during the alginate extraction step on alginates yield and quality were studied.
Abstract: The effect of temperature (70, 80, 90C) and time (1‐9 h) during the alkaline extraction step on alginate yield and quality were studied. The alginate yield increased with time and maximum yield was obtained after 3.5 h treatment, ranging from 19.4% at 70C to 21.9% at 90C. The viscosity of the alginate produced was inversely correlated with the temperature and time. At 70C the slope of the curve was almost zero (753 to 923 mPa s); at 90 Ct he viscosity loss was 154 mPa s per hour during the first two hours, reducing from 523 to 86 mPa s after 5 h; 80 C yielded values between those for 70C and 90C. The best conditions for alkaline extraction were using pH 10 at 80C for two hours. The curves obtained gave useful information for controlling the viscosity of the alginate during production. It was found that viscosity of the paste formed during alkaline extraction (‘process viscosity’) was the best parameter to determine the reaction rate during extraction. Alginate yield increased during filtration time from 17.6% to 23.7% after 55 min at 70C. In this step the viscosity of the alginate obtained remained almost constant (522‐610 mPa s), indicating no degradation of the products during filtration. The best dilution to filter the alginate extract was obtained at 45 mPa s. Diatomaceous earth (Celite) and expanded lava (Perlite) were tested as filter aids. Expanded lava was the best filter aid, using 1 kg per kilogram of alginate produced. Three methods were studied to separate the alkaline-insoluble residues after extraction: filtration, centrifugation, flocculation, and combinations of them. The best system found was filtration with flocculant in a rotary vacuum filter, with a knife advance of 0.1 mm every 3.5 seconds and drum rotation of 2 rpm, yielding an average filtration flow rate of 10.5 L min 1 .
TL;DR: Determination of mycosporine-like amino acids (MAAs)before and during exposure to solar simulated irradiation showed a high initial concentration of MAAs but no increase due to the irradiance treatment, which led to a large decrease in quantum yield after short periods of irradiation.
Abstract: Porphyra umbilicalis was cultured under constant light conditions but showed a diurnal pattern in chlorophyll fluorescence. Photoinhibition after light treatment was determined by PAM fluorescence measurements. Treatment with only UV irradiation caused a slow but steady decline in the effective photosynthetic quantum yield from which there was no recovery. Solar simulated irradiation led to a large decrease in quantum yield after short periods of irradiation; partial recovery occurred after shading the samples. No significant difference was found between samples exposed to PAR only or to PAR + UV-A and/or UV-B irradiation. Determination of mycosporine-like amino acids (MAAs)before and during exposure to solar simulated irradiation showed a high initial concentration of MAAs but no increase due to the irradiance treatment.
TL;DR: The chemical structure and the hydrodynamic properties play a determinant role on the rheology of these carrageenans, and κ-Carrageenans from the Gigartinaceae displayed good gelling properties, while T. crinitus displayed the properties of ’random coil' only at high temperatures.
Abstract: The chemical and gel characteristics of carrageenans isolated from the most abundant algal species growing on the Russian Pacific coast – Chondrus pinnulatus, C. armatus and Iridaea cornucopiae belonging to the Gigartinaceae and Tichocarpus crinitus from the Tichocarpaceae were investigated. The polysaccharides were identified by FTIR and NMR spectroscopy as predominantly κ-carrageenans with traces of ι-type (Gigartinaceae) and κ / β-type repeating structures (Tichocarpaceae) together with a small quantity of λ-carrageenan (10%). The chemical structure and the hydrodynamic properties play a determinant role on the rheology of these carrageenans. κ-Carrageenans from the Gigartinaceae displayed good gelling properties. The highest gel strength was obtained from C. pinnulatus (1232.7 Pa) at a 2.5% polymer concentration, while carrageenans from the Tichocarpaceae formed very weak gels (77.4 Pa) at the same concentration. Optimum gel characteristics were found with 1.0–2.0% KCI concentrations for kappa- carrageenans from Gigartinaceae and 0.75% for T. crinitus. The flow curves of λ-carrageenans solutions from the Gigartinaceae were similar, all between 20 and 65 °C, and characteristic of conformational disordered ‘random coil’ polysaccharides. Carrageenans from T. crinitus displayed the properties of ’random coil' only at high temperatures.
TL;DR: The glycosylation of protein extract, which was especially marked in February, could explain the differences in behaviour of U. armoricana proteins in response to the digestive action of human enzymes.
Abstract: The in vitro digestibility of Ulva armoricana proteins by trypsin, chymotrypsin and human intestinal juice was determined to evaluate their nutritional value. The amino acid composition of the protein fraction and its changes during a sampling period from October to February were also studied. Some differences in the protein pattern shown by SDS PAGE were found in different months, such as the presence of a 54 kDa protein in February. The protein fraction is composed mainly of aspartic and glutamic acids (24–35% of protein fraction, according to season) and the essential amino acids constitute 27–36% of the total fraction. The efficiencies of trypsin and chymotrypsin in Ulva protein digestion are comparable. Only four proteins with apparent molecular weights of 86, 68, 40, and 29 KDa are digested by these proteolytic systems. The proteins from the October sample were more sensitive to chymotrypsin than those from the February sample. For instance, two proteins with apparent molecular weights of 100 and 67 kDa were weakly digested by chymotrypsin in the February extract, were fully digested in the October sample. The February sample differed from two others in the presence of glycosylated proteins, most of which have apparent molecular weights higher than 43 KDa. With the October sample, the activity of human intestinal juice was more effective than two other proteolytic systems. This is especially evident with a 27 kDa protein, which was only partially digested by the intestinal liquid and not digested by chymotrypsin or trypsin. However, human intestinal juice in the February apparently did not attack the 27 kDa protein. These data suggest a change in protein structure making it less sensitive to human intestinal juice. The glycosylation of protein extract, which was especially marked in February, could explain the differences in behaviour of U. armoricana proteins in response to the digestive action of human enzymes.
TL;DR: Bioassays using Euglena gracilis suggest that the inhibitory compounds are not derived from the phototransformation of straw decomposition products and do not act primarily by inhibiting photosynthesis.
Abstract: Decomposing barley straw has previously been shown to inhibit the growth of a limited number of algae under both laboratory and field conditions. Bioassays were conducted on a range of algae to evaluate their relative sensitivities to straw-derived inhibitor(s). A range of sensitivities was found, including some species that were resistant to the straw-derived inhibitor(s). A microcystin-producing strain of Microcystis aeruginosa was very susceptible to decomposing barley straw. Bioassays using Euglena gracilis suggest that the inhibitory compounds are not derived from the phototransformation of straw decomposition products and do not act primarily by inhibiting photosynthesis. Susceptibility to barley straw appears not to be related to general taxonomic or structural features. Possible implications for algal populations in natural freshwaters are briefly discussed.
TL;DR: It is demonstrated that several species of Eucheuma contain high yields of lectins homologous between species, suggesting that the genus as a whole may be considered as a valuable source of lectin proteins.
Abstract: We previously reported that the red alga Eucheuma serra contains large amounts of mitogenic isolectins (ESA-1 and ESA-2), the hemagglutinating activities of which were strongly inhibited by glycoproteins bearing high mannose-type N-glycans. We therefore further examined two other species, E. amakusaensis and E. cottonii. Several lectins were isolated easily by a combination of extraction with aqueous ethanol, precipitation with cold ethanol, gel filtration, and ion exchange chromatography from both species, respectively. The purified lectins were designated as EAA-1, EAA-2, EAA-3, ECA-1 and ECA-2 after the specific names of both algae. The yields of EAAs and ECAs were as high as 2.8 and 2.7 mg g−1 of dry tissue, respectively, indicating that both species would also be good sources for high lectin yields. The five purified lectins shared the same properties in hemagglutinating activity, mitogenic activity, and hemagglutination-inhibition test in which glycoproteins bearing high mannose-type N-glycans were the most inhibitory. They also had almost identical molecular weight and 20 N-terminal amino acid sequence to each other and to those of ESAs, and only differed in the isoelectric point, indicating that they are isolectins to each other. The study thus demonstrated that several species of Eucheuma contain high yields of lectins homologous between species, suggesting that the genus as a whole may be considered as a valuable source of lectin proteins.
TL;DR: Ssu rRNA gene structure was classified into four types by the presence and absence of intron(s) and exon nucleotide sequences were identical within the same species, but differed among species.
Abstract: The complete nucleotide sequences of ssu rRNA genes were determined for nine species of Porphyra. Ssu rRNA gene structure was classified into four types by the presence and absence of intron(s). Gene structure even differed within the same species. Exon nucleotide sequences were identical within the same species, but differed among species. Seventeen species of Porphyra were discriminated by comparing the sequences of these diversified regions, using the results of this study and previous studies.