Ulva rigida (Ulvales,Chlorophyta) tank culture as biofilters for dissolved inorganic nitrogen from fishpond effluents

Ulva rigida was cultivated in 7501 tanks at different densities with direct and continuous inflow (at 2, 4, 8 and 12 volumes d^–1) of the effluents from a commercial marine fishpond (40 metric tonnes, Tm, of Sparus aurata, water exchange rate of 16 m³ Tm^–1) in order to assess the maximum and optimum dissolved inorganic nitrogen (DIN) uptake rate and the annual stability of the Ulva tank biofiltering system. Maximum yields (40 g DW m^–2 d^–1) were obtained at a density of 2.5 g FW 1^–1 and at a DIN inflow rate of 1.7 g DIN m^–2 d^–1. Maximum DIN uptake rates were obtained during summer (2.2 g DIN M^–2 d^–1), and minimum in winter (1.1 g DIN m^–2 d^–1) with a yearly average DIN uptake rate of 1.77 g DIN m^–2 d^–1 At yearly average DIN removal efficiency (2.0 g DIN m^–2 d^–1, if winter period is excluded), 153 m² of Ulva tank surface would be needed to recover 100% of the DIN produced by 1 Tm of fish.Abbreviations DIN= dissolved inorganic nitrogen (NH _inf4 ^sup+ + NO _inf3 ^sup– + NO _inf2 ^sup– ); - FW= fresh weight; - DW= dry weight; - PFD= photon flux density; - V= DIN uptake rate     

Forecasting infections of the red rot disease on Porphyra yezoensis Ueda (Rhodophyta) cultivation farms

Pythium porphyrae is a fungal pathogen responsible for red rot disease of the seaweed Porphyra (Rhodophyta). Infection forecasts of Porphyra by P. porphyrae were estimated from the epidemiological observations of Porphyra thalli and numbers of zoospore of P. porphyrae in laboratory and cultivation areas. Four features of forecasting infections were determined by relating zoospore concentrations to the incidence of thallus infection; infection (in more than 1000 zoospores L⁻¹), microscopic infection [less than 2 mm in diameter of lesion (in from 2000 to 3000 zoospores L⁻¹)], macroscopic infection [more than 2 mm in diameter of lesion (in from 3000 to 4000 zoospores L⁻¹), and thallus disintegration (in more than 4000 zoospores L⁻¹). High zoospore concentrations led to more infection. The tendency that zoospore concentration of P. porphyrae increased with the rate of infection of Porphyra thalli was generally observed in forecasting infections in both the laboratory and in cultivation areas. Based on the Porphyra cultivation areas, the accuracy and consistency of forecasting infections suggest that this method could be employed to manage and control red rot disease.     

Biofiltering efficiency, uptake and assimilation rates of Ulva clathrata (Roth) J. Agardh (Clorophyceae) cultivated in shrimp aquaculture waste water

The growth, biofiltering efficiency and uptake rates of Ulva clathrata were studied in a series of outdoor tanks, receiving waste water directly from a shrimp (Litopenaeus vannamei) aquaculture pond, under constant aeration and two different water regimes: (1) continuous flow, with 1 volume exchange a day (VE day^-1) and (2) static regime, with 1 VE after 4 days. Water temperature, salinity, pH, dissolved inorganic nitrogen (DIN), phosphate (PO₄), chlorophyll-a (chl-a), total suspended solids (TSS), macroalgal biomass (fresh weight) and tissue nutrient assimilation were monitored over 12 days. Ulva clathrata was highly efficient in removing the main inorganic nutrients from effluent water, stripping 70–82% of the total ammonium nitrogen (TAN) and 50% PO₄ within 15 h. Reductions in control tanks were much lower (Tukey HSD, P < 0.05). After 3 days, the mean uptake rates by the seaweed biomass under continuous flow were 3.09 mg DIN g DW day⁻¹ (383 mg DIN m⁻² day⁻¹) and 0.13 mg PO₄ g DW day⁻¹ (99 mg PO₄ m⁻² day⁻¹), being significantly higher than in the static regime (Tukey HSD, P < 0.05). The chl-a decreased in seaweed tanks, suggesting that U. clathrata inhibited phytoplankton growth. Correlations between the cumulative values of DIN removed from the water and total nitrogen assimilated into the seaweed biomass (r = 0.7 and 0.8, P < 0.05), suggest that nutrient removal by U. clathrata dominated over other processes such as phytoplankton and bacterial assimilation, ammonia volatilization and nutrient precipitation.     

Productivity, CO2/O2 exchange and hydraulics in outdoor open high density microalgal (Chlorella sp.) photobioreactors operated in a Middle and Southern European climate

Two variants of open photobioreactors were operated at surface-to-volume ratios up to 170 m⁻¹. The mean values for July and September obtained for photobioreactor PB-1 of 224 m² culture area (length 28 m, inclination 1.7%, thickness of algal culture layer 6 mm), operated in Třeboň (49^∘N), Czech Republic, were: net areal productivity, P _net = 23.5 and 11.1 g dry weight (DW) m⁻² d⁻¹; net photosynthetic efficiency (based on PAR – Photosynthetic Active Radiation), η = 6.48 and 5.98%. For photobioreactor PB-2 of 100 m² culture area (length 100 m, inclination 1.6%, thickness of algal culture layer 8 mm) operated in Southern Greece (Kalamata, 37^∘N) the mean values for July and October were: P _net = 32.2 and 18.1 g DW m⁻² d⁻¹, η = 5.42 and 6.07%. The growth rate of the alga was practically linear during the fed-batch cultivation regime up to high biomass densities of about 40 g DW L⁻¹, corresponding to an areal density of 240 g DW m⁻² in PB-1 and 320 g DW m⁻² in PB-2. Night biomass loss (% of the daylight productivity, P _L) caused by respiration of algal cells were: 9–14% in PB-1; 6.6–10.8% in PB-2. About 70% of supplied CO₂ was utilized by the algae for photosynthesis. The concentration of dissolved oxygen (DO) increased from about 12 mg L⁻¹ at the beginning to about 35 mg L⁻¹ at the end of the 100 m long path of suspension flow in PB-2 at noon on clear summer days. Dissipation of hydraulic energy and some parameters of turbulence in algal suspension on culture area were estimated quantitatively.     

Effect of irradiation intensity on cell growth and kalata B1 accumulation in <Emphasis Type="Italic">Oldenlandia affinis</Emphasis> cultures

Light irradiation had remarkable effects on callus growth of Oldenlandia affinis with an optimum intensity of 35 μmol m⁻² s⁻¹. Biosynthesis of kalata B1, the main cyclic peptide in O. affinis, was induced and triggered with rising irradiation intensities. The highest concentration of kalata B1, 0.49 mg g⁻¹ DW characterised by the maximum productivity of 3.88 μg per litre and day was analysed at 120 μmol m⁻² s⁻¹, although callus growth was repressed. The light saturation point was established to be 35 μmol m⁻² s⁻¹, where kalata B1 productivity was in a similar order (3.41 μg per day) due to the higher growth index. O. affinis suspension cultures were shown to accumulate comparable specific kalata B1 concentrations in a delayed growth associated production pattern. These were dependent on irradiation intensity (0.16 mg g⁻¹ at 2 μmol m⁻² s⁻¹; 0.28 mg g⁻¹ at 35 μmol m⁻² s⁻¹). The batch cultivation process resulted in a maximum productivity of 27.30 μg per litre and day with culture doubling times of 1.16 d⁻¹. Submers operation represented a 8-fold product enhancement compared to callus cultivation.     

Effects of temperature and ammonium on growth,pigment production and nitrogen uptake by four species of <Emphasis Type="BoldItalic">Porphyra</Emphasis> (Bangiales,Rhodophyta) native to the New England coast

Porphyra is one of the world’s most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta, P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities (100–150 μmol photons m⁻²s⁻¹) and six combinations of ammonium (25 and 250 μmoles L⁻¹) and temperature (10, 15 and 20°C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day⁻¹. Phycoerythrin (PE) content was higher at 10°C and 250 μmoles L⁻¹ in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g⁻¹ FW⁻¹) and P. umbilicalis (26 mg g⁻¹ FW⁻¹) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on average 1.45% higher at 250 μmoles L⁻¹ than at 25 μmoles L⁻¹ ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10°C and 250 μmoles L⁻¹ ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture.     

Integrated outdoor culture of two estuarine macroalgae as biofilters for dissolved nutrients from <Emphasis Type="Italic">Sparus auratus</Emphasis> waste waters

An integrated outdoor cultivation of two macroalgal species: Ulva rotundata (Chlorophyta) and Gracilariopsis longissima (Rhodophyta) was designed. The macroalgae were cultured in effluents from an intensive marine culture (growout phase) of gilthead seabream Sparus aurata. The biomass evolution of the algal tanks followed a logistic curve, where the approach to the maximum stocking density of seaweeds was governed by thalli self-shading, as nutrient limitation in the cultivation tank was unlikely. The maximum stocking density of the system was approximately 27.8 g U. rotundata L⁻¹ (16.7 Kg m⁻²) and 11.9 g G. longissima L⁻¹ (7.12 Kg m⁻²). Yield was more than 3 times higher in U. rotundata than in G. longissima. Overall, U. rotundata removed a greater percentage of phosphate (8.9%) and total dissolved inorganic nitrogen (54%) flowing into the algal tanks than G. longissima. The latter species biofiltered approximately 3.2% of phosphate and 17% of the total dissolved inorganic nitrogen input. However, mean nutrient uptake rates on wet weight basis were usually higher in G. longissima than in U. rotundata. The production of total oxidised nitrogen in the algal tanks, considered as being the nitrification rate occurring on the algal fronds by nitrifying bacteria, was less than half of the ammonium uptake by the macroalgae, suggesting that seaweeds competed efficiently for ammonia against the nitrifyers. The biofiltration during a diel cycle showed that mean phosphate biofiltration was lower than 4.5% in the two species whereas ammonium was biofiltered efficiently (up to 67%), especially in U. rotundata. The metal and heavy metal content in the algal tissue at the end of the monitoring period suggested no metal contamination of tissues so that both macroalgal species could be used in the food industry. The study reveals the value of ecological engineering techniques in reducing the dissolved nutrient content in effluents from the fish farm, with the prospect of a better management practises, based on integrated mariculture designs, being developed by the local farmers.     

The relative contribution of symbiotic N2 fixation and other nitrogen sources to grassland ecosystems along an altitudinal gradient in the Alps

The significance of symbiotic N₂ fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps. The total annual symbiotic N₂ fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition). The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from 15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline in the activity of symbiotic N₂ fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N₂ fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since an addition of NH₄ ⁺ or NO₃ ⁻ fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N₂ fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m⁻² yr⁻¹) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m⁻² yr⁻¹) and wet deposition (0.4 g to 0.6 g m⁻² yr⁻¹) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic N₂ fixation (at least 0.1 g N m⁻² yr⁻¹) and wet deposition (0.3 g N m⁻² yr⁻¹) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m⁻² yr⁻¹). At high altitudes, wet N deposition and symbiotic N₂ fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear to be much less important. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cultivation of the brown alga <Emphasis Type="Italic">Hizikia fusiformis</Emphasis> (Harvey) Okamura: stress resistance of artificially raised young seedlings revealed by chlorophyll fluorescence measurement

Commercial farming of the intertidal brown alga Hizikia fusiformis (Harvey) Okamura in China and South Korea in the sea depends on three sources of seedlings: holdfast-derived regenerated seedlings, young plants from wild population and zygote-derived seedlings. Like many successfully farmed seaweed species, the sustainable development of Hizikia farming will rely on a stable supply of artificial seedlings via sexual reproduction under controlled conditions. However, the high rate of detachment of seedlings after transfer to open sea is one of the main obstacles, and has limited large-scale application of zygote-derived seedlings. To seek the optimal condition for growing seedlings on substratum in land-based tanks for avoidance of detachment in this investigation, young seedlings were grown in both outdoor tanks exposed directly to sunlight and in indoor raceway tanks in reduced, filtered sunlight. Results showed that young seedlings, immediately after fertilization, could withstand a daily fluctuation of direct solar irradiance up to a level of 1800 μmol photons m⁻² s⁻¹, and maintained a faster growth rate than seedlings grown in indoor tanks. Detailed experiments by use of chlorophyll fluorescence measurements further demonstrated that the overnight (12 h) recovery of optimal fluorescence quantum yield (F_v/F_m) of seedlings after 1 h treatment at 40°C was 98%, and the 48 h recovery of F_v/F_m of seedlings after 1 h exposure to 1800 μmol m⁻² s⁻¹ was 92%. Forty-one-day-old seedlings showed no significant decrease of optimal fluorescence quantum yield at salinity ranging from 30 to 5 ppt for a treatment up to 17 h. Six-hour desiccation treatment did not have any influence on the optimal fluorescence quantum yield. Exposure to 18 mmol L⁻¹ sodium hypochlorite for 10 min did not damage the PSII efficiency, and thus could be used to remove epiphytic algae. The strong tolerance of young seedlings to high temperature, high irradiance, low salinity and desiccation found in this investigation supports the view that mass production of Hizikia seedlings should be performed in ambient light and temperature instead of in shaded greenhouse tanks.     

Excess irradiance causes early symptoms of senescence during leaf expansion in photoautotrophically <Emphasis Type="Italic">in vitro</Emphasis> grown tobacco plants

Photosynthetic parameters, growth, and pigment contents were determined during expansion of the fourth leaf of in vitro photoautotrophically cultured Nicotiana tabacum L. plants at three irradiances [photosynthetically active radiation (400–700 nm): low, LI 60 μmol m⁻² s⁻¹; middle, MI 180 μmol m⁻² s⁻¹; and high, HI 270 μmol m⁻² s⁻¹]. During leaf expansion, several symptoms usually accompanying leaf senescence appeared very early in HI and then in MI plants. Symptoms of senescence in developing leaves were: decreasing chlorophyll (Chl) a+b content and Chl a/b ratio, decreasing both maximum (F_V/F_M) and actual (Φ_PS2) photochemical efficiency of photosystem 2, and increasing non-photochemical quenching. Nevertheless, net photosynthetic oxygen evolution rate (P _N) did not decrease consistently with decrease in Chl content, but exhibited a typical ontogenetic course with gradual increase. P _N reached its maximum before full leaf expansion and then tended to decline. Thus excess irradiance during in vitro cultivation did not cause early start of leaf senescence, but impaired photosynthetic performance and Chl content in leaves and changed their typical ontogenetic course.     

Mass production of bacterial communities adapted to the degradation of volatile organic compounds (TEX)

This study focuses on the mass cultivation of bacteria adapted to the degradation of a mixture composed of toluene, ethylbenzene, o-, m- and p-xylenes (TEX). For the cultivation process Substrate Pulse Batch (SPB) technique was adapted under well-automated conditions. The key parameters to be monitored were handled by LabVIEW software including, temperature, pH, dissolved oxygen and turbidity. Other parameters, such as biomass, ammonium or residual substrate concentrations needed offline measurements. SPB technique has been successfully tested experimentally on TEX. The overall behavior of the mixed bacterial population was observed and discussed along the cultivation process. Carbon and nitrogen limitations were shown to affect the integrity of the bacterial cells as well as their production of exopolymeric substances (EPS). Average productivity and yield values successfully reached the industrial specifications, which were 0.45 kg_DW m⁻³ d⁻¹ and 0.59 g_DW g_C⁻¹, respectively. Accuracy and reproducibility of the obtained results present the controlled SPB process as a feasible technique.     

Recent trends in nori products and markets in Asia

Since 1960s, modern techniques for nori (Porhyra) cultivation, artificial seeding of conchospores, floatingnet cultivation and freeze storage of nets, have been introduced into Japan, Korea and China. Owing to recent developments of these techniques, mechanization of processing and adaptation of fast-growing varieties of Porphyra, annual yield of nori have increased rapidly. Individual problems have, however, arisen in each country. In Japan, as the result of overproduction of nori, the farmers' profit level has, in general, decreased. As a consequence, the number of nori farmers, especially among those who would enter the industry, has declined markedly, and this is currently a serious problem. In Korea, there is a pressing need to improve the quality of nori, which is more important than increasing production. In China, the technical level of producing high quality Porphyra through cultivation and processing high quality nori is relatively undeveloped. There is thus a critical requirement to develop basic techniques in both cultivation and processing of nori in China.     

Production of high-density Chlorella culture grown in fermenters

The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L⁻¹ in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L⁻¹ h⁻¹. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L⁻¹ in 26.5 h at a mean growth rate 3.37 g DW L⁻¹ h⁻¹. Mean specific growth rate μ was about 0.1 h⁻¹ in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from 0.8 to 81.6 g DW L⁻¹ in 66.5 h at a mean growth rate 1.22 g DW L⁻¹ h⁻¹ and μ = 0.07 h⁻¹. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities higher than 10 g DW L⁻¹) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L⁻¹) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)⁻¹. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency.     

Effect of temperature and irradiance on the uptake of ammonium and nitrate by <Emphasis Type="Italic">Laurencia brongniartii</Emphasis> (Rhodophyta,Ceramiales)

The effects of temperature (20, 24 and 28 °C) and irradiance (15 and 40 μmol photon m⁻² s⁻¹) on the nitrate and ammonium uptake rates of the subtropical red alga, Laurencia brongniartii, were investigated to prepare for tank cultivation. Nitrate uptake followed saturation kinetics and was faster at higher irradiances and temperatures. In contrast, ammonium uptake was linear over the experimental range and was not affected by an increase in temperature. A parameter, β, was calculated to compare substrate uptake rates of nitrate along the linear portion of the uptake curve with that of ammonium. For nitrate, β was lower at low irradiance and higher at high irradiance (β = 0.007 ± 0.003 and 0.030 ± 0.002 [μmol N L⁻¹ (μmol N g_ww⁻¹ d⁻)⁻¹], respectively). However, β was 0.023 ± 0.002 and 0.034 ± 0.002 [μmol N L⁻¹ (μmol N g_ww⁻¹ d⁻¹)⁻¹] for ammonium, suggesting a preference for ammonium over nitrate.     

Cadmium accumulation in relation to organic acids in leaves of Solanum nigrum L. as a newly found cadmium hyperaccumulator

The influence of various cadmium concentrations on organic acid levels in leaves of the Cd hyperaccumulator, Solanum nigrum L. and a closely related species, Solanum melongena L., were investigated. In particular, the relationship of organic acids with Cd accumulation in the two plants was investigated. The results showed that Cd accumulation in the shoots of S. nigrum was significantly higher than that of S. melongena. The accumulation of Cd in the leaves of S. nigrum ranged from 2.0 to 167.8 μg g⁻¹ dry weight (DW), but only from 1.2 to 64.0 μg g⁻¹ DW in S. melongena. Solanum melongena was considerably less tolerant to Cd than S. nigrum. Approximately 20% of the total Cd in S. nigrum leaves was water-soluble, suggesting that some accumulated Cd was associated with water-soluble compounds such as organic acids. Malic acid in the leaves of S. nigrum was the most abundant organic acid [up to 115.6–145.7 μmol g⁻¹ fresh weight (FW)], but this acid was not significantly affected by the Cd concentration in soil. However, the level of malic acid in S. melongena plants was much lower, only 16.3–75.4 μmol g⁻¹ FW. The significant positive correlations between total Cd and water-soluble Cd concentrations and both acetic and citric acid concentrations in the leaves of S. nigrum were observed. In contrast, there was no correlation between concentrations of the two acids and Cd concentrations in the leaves of S. melongena. These results indicated that acetic and citric acids in the leaves of S. nigrum might be related to its Cd hyperaccumulation.     

Photosynthetic Response of Carrots to Varying Irradiances

Response to irradiance of leaf net photosynthetic rates (P _N) of four carrot cultivars: Cascade, Caro Choice (CC), Oranza, and Red Core Chantenay (RCC) were examined in a controlled environment. Gas exchange measurements were conducted at photosynthetic active radiation (PAR) from 100 to 1 000 μmol m⁻² s⁻¹ at 20 °C and 350 μmol (CO₂) mol⁻¹(air). The values of P _N were fitted to a rectangular hyperbolic nonlinear regression model. P _N for all cultivars increased similarly with increasing PAR but Cascade and Oranza generally had higher P _N than CC. None of the cultivars reached saturation at 1 000 μmol m⁻² s⁻¹. The predicted P _N at saturation (P _Nmax) for Cascade, CC, Oranza, and RCC were 19.78, 16.40, 19.79, and 18.11 μmol (CO₂) m⁻² s⁻¹, respectively. The compensation irradiance (I _c) occurred at 54 μmol m⁻² s⁻¹ for Cascade, 36 μmol m⁻² s⁻¹ for CC, 45 μmol m⁻² s⁻¹ for Oranza, and 25 μmol m⁻² s⁻¹ for RCC. The quantum yield among the cultivars ranged between 0.057–0.033 mol(CO₂) mol⁻¹(PAR) and did not differ. Dark respiration varied from 2.66 μmol m⁻² s⁻¹ for Cascade to 0.85 μmol m⁻² s⁻¹ for RCC. As P _N increased with PAR, intercellular CO₂ decreased in a non-linear manner. Increasing PAR increased stomatal conductance and transpiration rate to a peak between 600 and 800 μmol m⁻² s⁻¹ followed by a steep decline resulting in sharp increases in water use efficiency. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of macroelements and nitrogen source on biomass accumulation and withanolide-A production from cell suspension cultures of <Emphasis Type="Italic">Withania somnifera</Emphasis> (L.) Dunal

Withania somnifera is an important medicinal plant that contains withanolides and withaferins, both bioactive compounds. We have tested the effects of macroelements and nitrogen source in W. somnifera cell suspension cultures with the aim of optimizing the production of biomass and withanolide A. The effects of the macroelements NH₄NO_3, KNO_3, CaCl_2, MgSO₄ and KH₂PO₄ at concentrations of 0.0, 0.5, 1.0, 1.5 and 2.0× strength and of the nitrogen source [NH₄ ⁺/NO₃ ⁻ (mM/mM) ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20, and 14.38/37.60 (mM)] in Murashige and Skoog medium were tested for biomass and withanolide A production. The highest accumulation of biomass [147.81 g l⁻¹ fresh weight (FW) and 14.02 g l⁻¹ (dry weight (DW)] was recorded in the medium containing a 0.5× concentration of NH₄NO₃, and the highest production of withanolide A content was recorded in the medium with 2.0× KNO₃ (4.36 mg g⁻¹ DW). The NH₄ ⁺/NO₃ ⁻ ratio also influenced cell growth and withanolide A production, with both parameters being larger when the NO₃ ⁻ concentration was higher than that of NH₄ ⁺. Maximum biomass growth (110.45 g l⁻¹ FW and 9.29 g l⁻¹ DW) was achieved at an NH₄ ⁺/NO₃ ⁻ ratio of 7.19/18.80, while withanolide A production was greatest (3.96 mg g⁻¹ DW) when the NH₄ ⁺/NO₃ ⁻ ratio was 14.38/37.60 mM.     

Enhanced iturin A production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> and its effect on suppression of the plant pathogen <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

The behavior of Streptomyces peucetius var. caesius N47 was studied in a glucose limited chemostat with a complex cultivation medium. The steady-state study yielded the characteristic constants μ _max over 0.10 h⁻¹, Y _XS 0.536 g g⁻¹, and m_S 0.54 mg g⁻¹ h⁻¹. The product of secondary metabolism, ɛ-rhodomycinone, was produced with characteristics Y _PX 12.99 mg g⁻¹ and m _P 1.20 mg g⁻¹ h⁻¹. Significant correlations were found for phosphate and glucose consumption with biomass and ɛ-rhodomycinone production. Metabolic flux analysis was conducted to estimate intracellular fluxes at different dilution rates. TCA, PPP, and shikimate pathway fluxes exhibited bigger values with production than with growth. Environmental perturbation experiments with temperature, airflow, and pH changes on a steady-state chemostat implied that an elevation of pH could be the most effective way to shift the cells from growing to producing, as the pH change induced the biggest transient increase to the calculated ɛ-rhodomycinone flux.     

Chlorophyll fluorescence imaging of photosynthetic activity in sun and shade leaves of trees

The differences in pigment levels, photosynthetic activity and the chlorophyll fluorescence decrease ratio R _Fd (as indicator of photosynthetic rates) of green sun and shade leaves of three broadleaf trees (Platanus acerifolia Willd., Populus alba L., Tilia cordata Mill.) were compared. Sun leaves were characterized by higher levels of total chlorophylls a + b and total carotenoids x + c as well as higher values for the weight ratio chlorophyll (Chl) a/b (sun leaves 3.23–3.45; shade leaves: 2.74–2.81), and lower values for the ratio chlorophylls to carotenoids (a + b)/(x + c) (with 4.44–4.70 in sun leaves and 5.04–5.72 in shade leaves). Sun leaves exhibited higher photosynthetic rates P _N on a leaf area basis (mean of 9.1–10.1 μmol CO₂ m⁻² s⁻¹) and Chl basis, which correlated well with the higher values of stomatal conductance G _s (range 105–180 mmol m⁻² s⁻¹), as compared to shade leaves (G _s range 25–77 mmol m⁻² s⁻¹; P _N: 3.2–3.7 μmol CO₂ m⁻² s⁻¹). The higher photosynthetic rates could also be detected via imaging the Chl fluorescence decrease ratio R _Fd, which possessed higher values in sun leaves (2.8–3.0) as compared to shade leaves (1.4–1.8). In addition, via R _Fd images it was shown that the photosynthetic activity of the leaves of all trees exhibits a large heterogeneity across the leaf area, and in general to a higher extent in sun leaves than in shade leaves.     

Cultivation of the green alga, Codium fragile (Suringar) Hariot, by artificial seed production in Korea

Codium fragile (Suringar) Hariot is an edible green alga farmed in Korea using seed stock produced from regeneration of isolated utricles and medullary filaments. Experiments were conducted to reveal the optimal conditions for nursery culture and out-growing of C. fragile. Sampling and measurement of underwater irradiance were carried out at farms cultivating C. fragile at Wando, on the southwestern coast of Korea, from October 2004 to August 2005. Growth of erect thalli and underwater irradiance were measured over a range of depths for three culture stages. During the nursery cultivation stage (Stage I), growth rate was greatest at 0.5 m depth (0.055 ± 0.032 mm day⁻¹), where the average midday irradiance over 60 days was 924 ± 32 μmol photons m⁻² s⁻¹. During the pre-main cultivation stage (Stage II), the greatest growth rate occurred at a depth of 2 m (0.113 ± 0.003 mm day⁻¹) with an average irradiance of 248 ± 116 μmol photons m⁻² s⁻¹. For the main cultivation stage (Stage III) of the alga, thalli achieved the greatest increase in biomass at 1 m depth (7.2 ± 1.0 kg fresh wt m⁻¹). These results suggest that optimal growth at each cultivation stages of C. fragile could be controlled by depth of cultivation rope.