Sustainable, High-Yielding Outdoor Mass Cultures of Chaetoceros muelleri var. subsalsum and Isochrysis galbana in Vertical Plate Reactors

Continuous cultures of Chaetoceros muelleri and Isochrysis galbana were grown outdoors in flat plate-glass reactors in which light-path length (LPL) varied from 5 to 30 cm. High daily productivity (13 to 16 g cell mass per square meter of irradiated reactor surface) for long periods of time was obtained in reactors in which the optical path as well as cell density were optimized. 'Twenty centimeters was the optimal LPL, yielding the highest areal productivity of cell mass (g m^–2d^–1), eicosapentaenoic acid, and docosahexaenoic acid, which was identical with that previously found for polysaccharide production of Porphyridium and not far from the optimal LPL affecting maximal productivity in Nannochloropsis species. Relating the energy impinging on a given reactor surface area to the appropriate number of cells showed that the most efficient light dose per cell, obtained with the 20-cm LPL reactor, was approximately 2.5 times lower than the light dose available per cell in the 5-cm LPL reactor, in which a significant decline in areal cell density accompanied the lowest areal output of cell mass. The most effective harvesting regimen was in the range of 10% to 15% of culture volume harvested daily and replaced with fresh growth medium, resulting in a sustainable culture density of 24 × 10⁶ and 28 × 10⁶ cells/ml of C. muelleri and I. galbana, respectively.     

Characterization of growth and arachidonic acid production of Parietochloris incisa comb. nov (Trebouxiophyceae, Chlorophyta)

Arachidonic acid (AA) is a precursor of biologically activeprostaglandines and leukotrienes. The commercial source for AA at present is afungus, but the recently discovered coccoid green alga,Parietochlorisincisa comb. nov., in which over 90% of total AA is deposited intriacylglycerols, makes this species a potential candidate for commercialproduction of AA. We investigated the effect of the light-regime on cell-AAcontent and on culture productivity, by manipulating the intensity of the lightsource, the length of the light-path (LPL), and the population density ofcultures grown in flat plate glass reactors under both controlled laboratoryconditions (continuously illuminated) as well as outdoors. The effect ofnitrogen deprivation on culture content of AA and its productivity was alsostudied.In all experiments, the longer light-path reactors with the highest arealvolumes (L m^–2) yielded the highest culture-AA or the highestamount of AA harvested per illuminated reactor surface. Highest culture contentof AA was obtained in cultures exposed to strong light andnitrogen-deprivation.In contrast, highest cell-AA content was obtained in cultures receiving thelowest light-dose. Maximum culture content of AA obtained in the laboratory was2667 mg L^–1, reached after a 38-day growth period(of which the final 17 days took place in nitrogen-free medium), undercontinuous exposure to 2000 mol photon m^–2s^–1. Maximal culture content of AA outdoors wassignificantly lower compared with the maximum obtained in the laboratory.     

Growth characteristics of ultrahigh-density microalgal cultures

The physiological characteristics of cultures of very high cell mass (e.g. 10 g cell mass/L), termed “ultrahigh cell density cultures” is reviewed. A close relationship was found between the length of the optical path (OP) in flat-plate reactors and the optimal cell density of the culture as well as its areal (g m⁻² day⁻¹) productivity. Cell-growth inhibition (GI) unfolds, as culture density surpasses a certain threshold. If it is constantly relieved, a 1.0 cm OP reactor could produceca. 50% more than reactors with longer OP,e.g. 5 or 10 cm. This unique effect, discovered by Hu et al. [3], is explained in terms of the relationships between the frequency of the light-dark cycle (L-D cycle), cells undergo in their travel between the light and dark volumes in the reactor, and the turnover time of the photosynthetic center (PC). In long OP reactors (5 cm and above) the L-D cycle time may be orders of magnitude longer than the PC turnover time, resulting in a light regime in which the cells are exposed along the L-D cycle, to long, wasteful dark periods. In contrast, in reactors with an OP ofca. 1.0 cm, the L-D cycle frequency approaches the PC turnover time resulting in a significant reduction of the wasteful dark exposure time, thereby inducing a surge in photosynthetic efficiency. Presently, the major difficulty in mass cultivation of ultrahigh-density culture (UHDC) concerns cell grwoth inhibition in the culture, the exact nature of which is awaiting detailed investigation.     

Light-path length and population density in photoacclimation of Nannochloropsis sp. (Eustigmatophyceae)

Photoacclimation in the marine eustigmatophyte Nannochlropsis sp., used extensively as a food chaincomponent in aquaculture, was studied both in thelaboratory and outdoors. Cell-chlorophyll andcarotenoids were used as markers to assessphotoacclimation to strong light, as well as todecreasing growth irradiance due to cellproliferation. Focusing on practical aspects involvedin mass cultivation, three different approaches wereused as follows: (a) cultures initially exposed to lowlight (150 mol photon m^-2 s^-1) thentransferred to strong light (1000 to 3000 molphoton m^-2 s^-1); (b) initially low celldensity cultures grown in reactors of differentlight-paths, exposed to strong PFD, in the laboratoryand outdoors; (c) initially low or high cell densitycultures exposed to strong light. As has already beenestablished in many reports, cell-chlorophyllrepresented a sensitive parameter in assessing cellresponse to changes in the intensity of the lightsource as well as to modifications in the light regimeto which the cells were exposed. Cell-chlorophyllconcentration sharply decreased initially upontransferring the culture from low PFD cell^-1 tohigh PFD cell^-1 due to either culture dilution(i.e. decrease in cell density and mutual shading) orto an increase in PFD. After some 7 days ofphotoacclimating to 2000 and 3000 mol photonm^-2 s^-1, chlorophyll a content began to riseat a much faster rate than cell number, which alsoincreased in response to the higher irradiance.Cell-chlorophyll in the culture exposed to 2000mol photon m^-2 s^-1 increased afteracclimation earlier and at a faster rate than in theculture exposed to 3000 mol photon m^-2s^-1, indicating the later irradiance affected astronger stress. The length of the reactor's lightpath exerted a decisive effect on cell response tostrong light through its influence on the light regimein the culture. Upon a sharp increase in PFD,carotenoids in the 1-cm reactor increased in muchhigher rate than chlorophyll, compared with the 3-cmlight path reactors. This marked difference in cellresponse to a shift-up in light was attributed to thevast variations in the light regime associated withdifferences in the length of the light path and areal density. Growth oflow cell density cultures ceased temporarily upontransfer to strong light, in contrast with high celldensity cultures transferred to strong light, whichcontinued growth without a lag.     

Light/dark cyclic movement of algal culture (<Emphasis Type="Italic">Synechocystis aquatilis</Emphasis>) in outdoor inclined tubular photobioreactor equipped with static mixers for efficient production of biomass

Synechocystis aquatilis SI-2 was grown outdoors in a 12.5cm diam. tubular photobioreactor equipped with static mixers. The static mixers ensured that cells were efficiently circulated between the upper (illuminated) and lower (dark) sections of the tubes. The biomass productivity varied from 22 to 45g m^–2d^–1, with an average of 35g m^–2d^–1, etc which corresponded to average CO₂ fixation rate of about 57 g CO₂ m^–2 d^–1. The static mixers not only helped in improving the biomass productivities but also have a high potential to lower the photoinhibitory effect of light during the outdoor cultures of algae. Revisions requested 27 July 2004; Revisions received 12 November 2004     

FIXED CARBON PARTITIONING IN THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA)

The main products of carbon fixation in the red algae are sulfated cell-wall polysaccharides, floridean starch, and low molecular weight (LMW) carbohydrates, mainly floridoside. In the red microalga Porphyridium sp., sulfated polysaccharide—cell bound and soluble—comprises up to 70% of the algal biomass. The purpose of this study was to elucidate the partitioning of fixed carbon in Porphyridium sp. toward the different products of carbon fixation. Using pulse-chase technique with [¹⁴C]bicarbonate, we followed ¹⁴C flow into the major compounds, namely, cell-wall polysaccharide, floridoside, starch, and protein, under various environmental conditions (i.e. carbon dioxide enrichment and nitrate starvation). ¹³C-NMR and gas chromatography analysis showed the main LMW product in Porphyridium sp. to be floridoside. After the short [¹⁴C]bicarbonate pulse (20 min), 42%–53% of total ¹⁴C uptake was initially found in floridoside. The appearance of ¹⁴C in the soluble polysaccharide was evident immediately at the end of the 20-min [¹⁴C]bicarbonate pulse. The specific radioactivity in the floridoside fraction declined by 80% after the 48-h chase, this decline being accompanied by increased labeling of starch and the soluble polysaccharide. In cells exposed to high CO₂ concentration, larger amounts of ¹⁴C (about twice as much) were channeled into starch and soluble polysaccharide than in cells under low CO₂ concentration. The most significant increase (1500%) in labeling during chase was found in the soluble polysaccharide of the nitrate-deprived cultures. It therefore seems likely that the large amounts of carbon incorporated by Porphyridium sp. cells into floridoside were subsequently used for the synthesis of macromolecular components. The data thus support the premise that floridoside serves as a dynamic carbon pool, which channels the fixed carbon toward polysaccharides and other end products according to the ambient conditions.     

Growth physiology of a marine nitrogen-fixing cyanobacterium (Nodularia harveyana) in outdoor culture

The performance ofNodularia harveyana, a N₂-fixing cyanobacterium isolated from seawater, has been studied outdoors in two different culture systems: open pond (OP) and tubular photobioreactor (TPR). The productivity in both devices was influenced by areal density. The maximum yield obtained was 12.0 g (d.wt) m^–2 day^–1 in OP and 14.0 g (d.wt) m^–2 day^–1 in TPR in August, corresponding to the highest solar radiation received. In a month-long experiment with the cyanobacterium cultivated in TPR at high circulation speed, a net increase in productivity was obtained over that at low circulation speed. The influence of temperature on the productivity of the cultures grown in open ponds and tubular photobioreactors has been investigated. The higher productivity obtained in TPR compared to OP was attributed to its better controlled temperature conditions. In outdoor culture the maximum nitrogenase activity did not coincide with the maximum light intensity, but occurred in early afternoon. The amount of carbohydrate accumulated during the day probably influenced the rate of dark nitrogenase activity and its duration in the night.     

Variation in some photosynthetic characteristics of microalgae cultured in outdoor thin-layered sloping reactors

In outdoor thin-layer sloping reactors algae are batch cultured and harvested at biomass concentrations of about 15 g (dw) I^-1 whereafter a portion is used as inoculum for the next cycle. Light saturation curves of the oxygen evolution (PII curves) of the algae were measured using diluted aliquots of suspension taken from the reactors. The maximum specific photosynthetic rates (P ^B _max) and the light intensity at the onset of saturated photosynthesis (I _k ) decreased whilst the maximum specific photosynthetic efficiency ( ^B ) increased with an increase in the biomass concentration, during the production cycle. These differences reflect transition from light- to dark-acclimated state of the algae that occurs as a result of an increase of the suspension concentration during the production cycle. During these experiments the thin-layered smooth sloping cultures (TLSS, culture depth 5–7 mm) had higher photosynthetic rates per volume than the thin-layered baffled sloping cultures (TLBS, culture depth 5–15 mm). This was ascribed to the higherP ^B _max values of the algae grown in the TLSS cultures, allowing them to utilise high incident irradiancies more effectively. However, the areal productivity of the TLBS was higher than the TLSS indicating a higher photosynthetic efficiency of the TLBS reactors. The specific productivity decreased rapidly with an increase in the biomass concentration, but the yield remained linear during the batch production cycle, even at high areal densities.     

Sulfated polysaccharides from brown seaweeds Saccharina japonica and Undaria pinnatifida: isolation, structural characteristics, and antitumor activity

During the last decade brown seaweeds attracted much attention as a source of polysaccharides, namely laminarans, alginic acids, and sulfated polysaccharides—fucoidans, with various structures and biological activities.In this study, sulfated polysaccharides were isolated from brown seaweeds Saccharina japonica (formerly named Laminaria) and Undaria pinnatifida and their antitumor activity was tested against human breast cancer T-47D and melanoma SK-MEL-28 cell lines.The sulfated polysaccharide form S. japonica was highly branched partially acetylated sulfated galactofucan, built up of (1→3)-α-l-fucose residues. The sulfated polysaccharide from U. pinnatifida was partially acetylated highly sulfated galactofucan consisting of (1→3)- or (1→3);(1→4)-α-l-fucose residues.Fucoidans from S. japonica and U. pinnatifida distinctly inhibited proliferation and colony formation in both breast cancer and melanoma cell lines in a dose-dependent manner. These results indicated that the use of sulfated polysaccharides from brown seaweeds S. japonica and U. pinnatifida might be a potential approach for cancer treatment.     

FLORIDOSIDE AS A CARBON PRECURSOR FOR THE SYNTHESIS OF CELL‐WALL POLYSACCHARIDE IN THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA)1

Although red algae are known to be obligatory photoautotrophs, the red microalga Porphyridium sp. was shown to assimilate and metabolize floridoside. A pulse‐chase experiment with [¹⁴C]floridoside showed that at the end of a 240‐min pulse, 70% of total ¹⁴C‐uptake by the cells remained in the floridoside fraction. To evaluate the assimilation of floridoside by Porphyridium sp. cells, we exposed Porphyridium sp. not only to [¹⁴C]floridoside but also to its constituents, [¹⁴C]glycerol and [¹⁴C]galactose, as compared with [¹⁴C]bicarbonate. The extent of incorporation of [¹⁴C] galactose by the Porphyridium sp. cells was insignificant (50–80 dpm·mL^?1), whereas uptake of ¹⁴C from [¹⁴C]glycerol into the algal cells was evident (2.4 × 10³ dpm·mL^?1) after 60 min of the pulse. The pattern of ¹⁴C distribution among the major constituent sugars, xylose, glucose and galactose, of the labeled soluble polysaccharide was dependent on the ¹⁴C source. The relative content of [¹⁴C]galactose in the soluble polysaccharide was highest (28.8%) for [¹⁴C]floridoside‐labeled culture and lowest (19.8%) for the [¹⁴C]glycerol‐labeled culture. Upon incubation of [¹⁴C]floridoside with a crude extract of a cell‐free system prepared from nonlabeled cells of Porphyridium sp., the label was indeed found to be incorporated into the sulfated polysaccharide. Our results suggested that the carbon metabolic pathway in Porphyridium sp. passes through the low molecular weight photoassimilatory product—floridoside—toward sulfated cell‐wall polysaccharide production.     

Optimizing the population density inIsochrysis galbana grown outdoors in a glass column photobioreactor

Particularly high population densities are readily sustainable in newly designed glass column reactors. The optimal density ofIsochrysis galbana in these columns in summer was 4.6 g L^–1 dry algal mass at which value the highest sustainable productivity obtained was a record of 1.6 g L^–1 d^–1. The population density exerted a direct effect on productivity: The higher the light intensity, the more pronounced was the dependence of the output rate on the population density, variations of 10%± from the optimal density resulting in a significant decline in productivity. The population density had also a very significant effect on the course of photoadaptation which took place during the first days after transferring the cultures from the laboratory to the outdoors. The output rate was lower by 5 to 35% on the first day of such transfer as compared to the light-adapted control. The higher the cell density, the faster was the process of photoadaptation as indicated by the rise of the productivity and O₂ tension to the control level. The potential for excess light damages was most prominent in the column reactors used, in which the light path was much reduced compared with that in open raceways. Significant photoinhibition took place at below optimal population density (2.8–3.8 g L^–1), and when cell density was further reduced (1.9 to 1.1 g L^–1), exposure to full sunlight caused photooxidative death within a few hours. The pattern of O₂ concentration in the culture that emerged along the day served as a useful indicator of photolimitation.Author for correspondence     

Responses of Porphyra linearis (Rhodophyta) to environmental factors under controlled culture conditions

The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 ^°C), low PPF (70–140 mol photon m^-2s^-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s^-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.     

Mass cultivation of Nannochloropsis sp. in annular reactors

A study was made on the mass cultivation of Nannochloropsis sp. in newly designed annular reactors operated under natural, artificial or combined illumination. The annular reactor consists of two 2-m-high Plexiglas cylinders of different diameter placed vertically one inside the other so as to form an annular culture chamber. Artificial illumination is supplied by lamps placed inside the inner cylinder. Two annular reactors of different diameter (50 and 91 cm), light path (4.5 and 3.0 cm) and illuminated surface area (5.3 and 9.3 m²) were experimented with. The effect of two different artificial light sources (fluorescent tubes and metal halide lamps) on culture productivity was investigated in both systems. The highest productivity on a per reactor basis (about 34 g (d. wt) reactor^–1 24 h^–1) was achieved with the larger reactor illuminated by a 400-W metal halide lamp. From February to May a 91-cm reactor illuminated only with natural light was operated in parallel with a 91-cm reactor subjected to combined illumination. Under natural illumination productivity increased from 16.6 g (d. wt) reactor^–1 d^–1 in February to 34.1 g (d. wt) reactor^–1 d^–1 in May. Under combined illumination productivity was 41.3 g (d. wt) reactor^–1 d^–1 in February and increased up to 48.3 g (d. wt) reactor^–1 d^–1 in May. Although the culture exposed to combined illumination always attained higher yields, the productivity gap between the two cultures decreased gradually along the season as solar radiation and minimum night temperatures increased. A 1200-L plant made of ten 50-cm annular reactors was set up and operated for two years with combined illumination yielding an average of 270 g of dry Nannochloropsis sp. biomass per day. More than 2000 L of concentrate suspension (50 g (d. wt) L^–1) of Nannochloropsis sp. were produced and successfully used by fish hatcheries as live feed for rotifers and for rearing seabream larvae with the green-water technique. This study indicates that the annular reactor can be profitably used for long-term cultivation of Nannochloropsis in temperate climates. Besides reliability and ease of operation, the main advantage of the system is that it can be used under natural illumination, yet artificial light can be also supplied to maintain high productivity levels in winter or on cloudy days.     

Biodegradation and detoxification of phenolic compounds by pure and mixed indigenous cultures in aerobic reactors

Degradation and detoxification of a mixture of persistent compounds (2-chlorophenol, phenol and m-cresol) were studied by using pure and mixed indigenous cultures in aerobic reactors. Biodegradation assays were performed in batch and continuous flow reactors. Biodegradation was evaluated by determining total phenols, ultraviolet spectrophotometry and chemical oxygen demand (COD). Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe the microbial community in the reactor. Detoxification was evaluated by using Daphnia magna toxicity tests. Individual compounds were degraded by pure bacteria cultures within 27 h. The mixture of 2-clorophenol (100 mgl⁻¹), phenol (50 mgl⁻¹) and m-cresol (50 mgl⁻¹) was degraded by mixed bacteria cultures under batch conditions within 36 h: 99.8% of total phenols and 92.5% of COD were removed; under continuous flow conditions 99.8% of total phenols and 94.9% of COD were removed. Mineralization of phenolic compounds was assessed by gas chromatography performed at the end of the batch assays and in the effluent of the continuous-flow reactor. Toxicity was not detected in the effluent of the continuous-flow reactor.     

Growth and carrageenan quality of <Emphasis Type="Italic">Kappaphycus striatum</Emphasis> var. <Emphasis Type="Italic">sacol</Emphasis> grown at different stocking densities,duration of culture and depth

Kappaphycus striatum var. sacol was grown in two separate studies: (1) at two stocking densities, and (2) at four different depths, each for three different durations of culture (30, 45 and 60 days) in order to determine the growth rate of the seaweed and evaluate the carrageenan content and its molecular weight. The results demonstrated that stocking density, duration of culture and depth significantly (P < 0.01) affected the growth rate, carrageenan content and molecular weight of K. striatum var. sacol. Decreasing growth rate was observed at both stocking densities and at four depths as duration of culture increased. A lower stocking density (500 g m⁻¹line⁻¹) showed a higher growth rate for the shortest durations, i.e. 30 days, as compared to those grown at a higher density. Likewise, decreasing growth rate was observed as depth increased, except at 50 cm after 60 days of culture. A 45-day culture period produced the highest molecular weight at both stocking densities (500 g m⁻¹line⁻¹ = 1,079.5 ± 31.8 kDa, 1,000 g m⁻¹line⁻¹ = 1,167 ± 270.6 kDa). ‘Sacol’ grown for 30 days at 50 cm (1,178 kDa) to 100 cm (1,200 kDa) depth showed the highest values of molecular weight of carrageenan extracted. The results suggested that K. striatum var. sacol is best grown at a stocking density of 500 g m⁻¹line⁻¹, at a depth of 50–100 cm, and for a duration of 30 days in order to provide the highest growth rate, carrageenan content and molecular weight.     

Optimization of a flat plate glass reactor for mass production of Nannochloropsis sp. outdoors

The relationships between areal (g m(-2) per day) and volumetric (g l(-1) per day) productivity of Nannochloropsis sp. as affected by the light-path (ranging from 1.3 to 17.0 cm) of a vertical flat plate glass photobioreactor were elucidated. In general, the shorter the length of the light-path (LP), the smaller the areal volume and the higher the volumetric productivity. The areal productivity in relation to the light-path, in contrast, yielded an optimum curve, the highest areal productivity was obtained in a 10 cm LP reactor, which is regarded, therefore, optimal for mass production of Nannochloropsis. An attempt was made to identify criteria by which to assess the efficiency of a photobioreactor in utilizing strong incident energy. Two basic factors which relate to reactor efficiency and its cost-effectiveness have been defined as (a) the total illuminated surface required to produce a set quantity of product and (b) culture volume required to produce that quantity. As a general guide line, the lower these values are, the more efficient and cost-effective the reactor would be. An interesting feature of this analysis rests with the fact that an open raceways is as effective in productivity per illuminated area as a flat-plate reactor with an optimal light path, both cultivation systems requiring ca. 85 m(2) of illuminated surface to produce 1 kg dry cell mass of Nannochloropsis sp. per day. The difference in light utilization efficiency between the two very different production systems involves three aspects - first, the open raceway requires ca. 6 times greater volume than the 10 cm flat plate reactor to produce the same quantity of cell-mass. Second, the total ground area (i.e. including the ground area between reactors) for the vertical flat plate reactor is less than one half of that occupied by an open raceway, indicating the former is more efficient, photosynthetically, compared with the latter. Finally, the harvested cell density is close to one order of magnitude higher in the flat plate reactor, which carries economic significance. The advantage of vertical lamination of photoautotrophic cells provided by vertical plate reactors, is thereby clearly seen. The optimal population density (i.e. which results in the highest areal productivity) in the 10 cm plate reactor was obtained by a daily harvest of 10% of culture volume, yielding an annual average of ca. 12.1 g dry wt. m(-2) per day (on the basis of the overall illuminated reactor surfaces, i.e. front and back) or 240 mg l(-1) per day.     

Sulfated polysaccharides from marine green algae Ulva conglobata and their anticoagulant activity

Sulfated polysaccharides from the green algae Ulva conglobata were isolated and prepared by extraction in hot water, precipitation with ethanol and purification by ion-exchange and size-exclusion column chromatography. The characterizations of the sulfated polysaccharides were defined, and containing 23.04–35.20% sulfate ester groups, 10.82–14.91% uronic acid and 3.82–4.51% protein. Gas chromatography analysis shows that the sulfated polysaccharides from Ulva conglobata are mainly consisted of rhamnose with variable contents of glucose and fucose, trace amounts of xylose, glactose and mannose. The anticoagulant properties of the sulfated polysaccharides were compared with those of heparin by studying the activated partial thromboplastin time using normal human plasma. The sulfated polysaccharide from Ulva conglobata collected in Qingdao, China is the most potent among the sulfated polysaccharides tested. The mechanism of anticoagulant activity mediated by the sulfated polysaccharides is due to the direct inhibition of thrombin and the potentiation of heparin cofactor II.     

Sulfated galactofucan from <Emphasis Type="Italic">Lobophora variegata</Emphasis>: Anticoagulant and anti-inflammatory properties

Sulfated polysaccharides (fucans and fucoidans) from brown algae show several biological activities, including anticoagulant and anti-inflammatory activities. We have extracted a sulfated heterofucan from the brown seaweed Lobophora variegata by proteolytic digestion, followed by acetone fractionation, molecular sieving, and ion-exchange chromatography. Chemical analyses and ¹³C-NMR and IR spectroscopy showed that this fucoidan is composed of fucose, galactose, and sulfate at molar ratios of 1:3:2. We compared the anticoagulant activity of L. variegata fucoidan with those of a commercial sulfated polysaccharide (also named fucoidan) from Fucus vesiculosus and heparin. The experimental inflammation models utilized in this work revealed that fucoidan from L. variegata inhibits leukocyte migration to the inflammation site. Ear swelling caused by croton oil was also inhibited when sulfated polysaccharides from F. vesiculosus and L. variegata were used. The precise mechanism of different action between homo-and heterofucans is not clear; nevertheless, the polysaccharides studied here may have therapeutic potential in inflammatory disorders. Published in Russian in Biokhimiya, 2008, Vol. 73, No. 9, pp. 1265–1273.     

Anti-apoptotic Activity of Laminarin Polysaccharides and their Enzymatically Hydrolyzed Oligosaccharides from Laminaria japonica

Laminarin polysaccharides (LP1) were prepared from Laminaria japonica, a marine brown alga with potential biological activities, by hot water extraction, ultrafiltration and gel chromatography; the molecular weights of the LP1s were between 5 and 10 kDa. Laminarin oligosaccharides (LO) derived by hydrolyzing LP1 with an endo-β-(1→3)-glucanase from Bacillus circulans were mainly di- and penta-oligosaccharides. Treatment of mouse thymocytes with LO or LP1 (1–4 mg ml⁻¹) suppressed apoptotic death around 3- or 2-fold and extended cell survival in culture at a rate of about 30 or 20%. A mouse cDNA microarray showing the genes coding for immune response proteins were induced and apoptotic cell death proteins were reduced significantly by LO provided preliminary information regarding the immunomodulatory mechanism of LO. These results suggest that laminarin oligosaccharides and polysaccharides can be utilized to develop new immunopotentiating substances and functional alternative medicines. Revisions requested 26 October 2005; Revisions received 19 December 2005     

Influence of areal density on β-carotene production by Dunaliella salina

High irradiance is probably the most important factor responsible for the massive accumulation of β-carotene by the halotolerant green alga Dunaliella salina. Operating outdoor cultures at optimal areal densities should result in maximal productivity. It is known that the optimal areal density is not fixed for all algae, where it could vary depending on the type of algae cultured, pond construction, turbulence and prevailing environmental conditions. At biomass concentrations below the optimum, more light per cell is available than that which could be absorbed by the biomass. These high light conditions should favour carotenogenesis and could result in higher β-carotene production rates. The results obtained clearly showed that over and above light and nutrient stress, an extremely important aspect is the residence time of the cells in the ponds. Longer residence times resulted in the development of larger cells, containing larger quantities of β-carotene. Productivity of biomass and β-carotene were about 70% higher at areal densities of 35–45 g m^-2, compared to areal densities of 15–25 g m^-2.