Predicting Epipelic Diatom Exopolymer Concentrations in Intertidal Sediments from Sediment Chlorophyll a

Abstract In many intertidal cohesive—sediment habitats, epipelic diatoms are the dominant microphytobenthic organisms. In such sediments, concentrations of colloidal carbohydrate [including the exopolymeric substances (EPS) produced by diatoms during motility] are closely correlated with the biomass (chlorophyll a) of epipelic diatoms. A model describing this relationship (log (conc. coll. carbo. + 1) = 1.40 + 1.02(log (chl. a conc. + 1)) was derived from published data. It was validated against published and unpublished data from 6 different estuaries, and accounted for 64.6% of the variation in sediment colloidal carbohydrate concentrations. The model was valid for intertidal habitats with cohesive sediments where epipelic diatoms constituted >50% of the microphytobenthic assemblage. In sites with noncohesive sediments, or where the microphytobenthic assemblage was dominated by other algal groups, the model was not applicable. The mean percentage of EPS in colloidal carbohydrate extracts varied between 11 and 37% for axenic cultures of epipelic diatoms (with higher values obtained during stationary phase), and between 22.7% and 24.3% for natural sediments dominated by epipelic diatoms. Assuming an EPS percentage of 25% in colloidal extracts yielded an EPS chl. a ratio of 2.62:1. Maximum rates of EPS production in diatom cultures occurred at the beginning of stationary phase (1.6–5.09 μg EPS μg⁻¹ chl a d⁻¹), with Nitzschia sigma having a significantly (P < 0.05) higher rate of production than N. frustulum, Navicula perminuta and Surirella ovata. Similar rates of EPS production were measured in the field. The dynamics of EPS production and loss on mudflats is discussed, with reference to the model and these production rates. Received: 25 February 1997; Accepted: 23 May 1997     

Large-scale cultivation of adventitious roots of Echinacea purpurea in airlift bioreactors for the production of chichoric acid, chlorogenic acid and caftaric acid

Adventitious roots of Echinacea purpurea were cultured in airlift bioreactors (20 l, 500 l balloon-type, bubble bioreactors and 1,000 l drum-type bubble bioreactor) using Murashige and Skoog (MS) medium with 2 mg indole butyric acid l⁻¹ and 50 g sucrose l⁻¹ for the production of chichoric acid, chlorogenic acid and caftaric acid. In the 20 l bioreactor (containing 14 l MS medium) a maximum yield of 11 g dry biomass l⁻¹ was achieved after 60 days. However, the amount of total phenolics (57 mg g⁻¹ DW), flavonoids (34 mg g⁻¹ DW) and caffeic acid derivatives (38 mg g⁻¹ DW) were highest after 50 days. Based on these studies, pilot-scale cultures were established and 3.6 kg and 5.1 kg dry biomass were achieved in the 500 l and 1,000 l bioreactors, respectively. The accumulation of 5 mg chlorogenic acid g⁻¹ DW, 22 mg chichoric acid g⁻¹ DW and 4 mg caftaric acids g⁻¹ DW were achieved with adventitious roots grown in 1,000 l bioreactors.     

Effects of macro elements and nitrogen source on biomass accumulation and bacoside A production from adventitious shoot cultures of <Emphasis Type="Italic">Bacopa monnieri</Emphasis> (L.)

The present work deals with optimization of adventitious shoot culture of Bacopa monnieri for the production of biomass and bacoside A and has investigated the effects of macro elements (NH₄NO_3, KNO_3, CaCl_2, MgSO₄ and KH₂PO₄) and nitrogen source [NH₄ ⁺/NO₃ ⁻] of Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium (MS) on accumulation of biomass and bacoside A content. Optimum number of adventitious shoots (99.33 shoots explant⁻¹), fresh weight (1.841 g) and dry weight (0.150 g) were obtained in the medium with 2.0× strength of NH₄NO₃. The highest production of bacoside A content was also recorded in the medium of 2.0× NH₄NO₃, which produced 17.935 mg g⁻¹ DW. The number of adventitious shoot biomass and bacoside A content were optimum when the NO₃ ⁻ concentration was higher than that of NH₄ ⁺. Maximum number of shoots (70.00 shoots explant⁻¹), biomass (fresh weight 1.137 g and dry weight 0.080 g) and also bacoside A content (27.106 mg g⁻¹ DW) were obtained at NH₄ ⁺/NO₃ ⁻ ratio of 14.38/37.60 mM. Overall, MS medium supplemented with 2.0× NH₄NO₃ is recommended for most efficient bacoside A production.     

Characterization of depth-related bacterial communities and their relationships with the environmental factors in the river sediments

To better understand the bacterial processes in river sediments, it is necessary to investigate the depth-related bacterial communities in the whole sediment profile. Sediment samples were collected to a depth of 25 cm from the Pearl River. Bacterial abundance, activity, cell-specific respiration rate, and diversity were measured, respectively, by 4′, 6-diamidino-2-phenylindole direct count, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining, electron transport system by CTC reduction, and denaturing gradient gel electrophoresis analysis of 16S rRNA amplification fragments. Results showed that the bacterial metabolism activities decreased with the sediment depth. The total bacterial abundance was highest in the surface sediment with 65.1 × 10⁷ cells g⁻¹, and decreased to 11.1 × 10⁷ cells g⁻¹ below 20 cm in the sample location that suffered from heavy sewage inputs. The active bacteria accounted for 7.50–46.7% of the total bacterial number and decreased with the sediment depth. Electron transport system by the CTC reduction showed that bacterial respiration rate declined from 1.093 μmol CTC-formazan h⁻¹ g⁻¹ in the surface sediment to a half in the bottom sediment, while the cell-specific respiration increased significantly with the depth from 3.56 to 93.75 fmol CTC-formazan cell⁻¹. The bacterial diversity also changed with the depth. Beta-Proteobacteria were the dominant species in the surface sediment, whereas Delta-Proteobacteria were the main species below 10 cm. Results of canonical correspondence analysis (CCA) indicated that the distribution of bacteria was affected by the combined effect of various dissolved inorganic matter, while the respiration rate was independent of the nutrient conditions. The specific bacterial distribution contributed to not only the nutrient cycle but also enhanced pollutant decomposition in sediment of the Pearl River. The results showed that some specific bacterial species had a strong activity in the deeper layers. Therefore, the metabolic functions of the deeper bacterial species should not be neglected.     

Characterization of extracellular polymeric substances from biofilm in the process of starting-up a partial nitrification process under salt stress

In this study, the characteristics of extracellular polymeric substance (EPS) fractions of biofilm during the process of establishing a partial nitrification under salt stress were analyzed in terms of concentrations, molecular weight distribution, and three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy. A partial nitrification was formed successfully with a salinity of 1%. Results indicated that the amount of total EPS increased from 54.2 mg g⁻¹ VSS⁻¹ on day 1 to 99.6 mg g⁻¹ VSS⁻¹ on day 55 due to the NaCl concentration changed from 0 to 10.0 g L⁻¹ in a biofilm reactor. The changes of loosely bound EPS (LB-EPS) compounds under different salt concentrations appeared to be more significant than those of the tightly bound EPS. A clear release of polysaccharides in the LB-EPS fraction was detected during the enhancement of salinity. This was considered as a protective response of bacteria to the salinity. Three fluorescence peaks were identified in the EEM fluorescence spectra of the EPS fraction samples. Two peaks were assigned to the protein-like fluorophores, and the third peak was located at the excitation/emission wavelengths of 275 nm/425–435 nm of the spectra of EPS fractions till the salinity maintained constant at 1%. This information is valuable for understanding the characteristics of EPS isolated from biomass in a saline nitrogen removal system.     

Phenylpropanoid production in callus and cell suspension cultures of <Emphasis Type="Italic">Buddleja cordata</Emphasis> Kunth

Plant tissue cultures represent a potential source for producing secondary metabolites. In this work, Buddleja cordata tissue cultures were established in order to produce phenylpropanoids (verbascoside, linarin and hydroxycinnamic acids), as these metabolites are credited with therapeutic properties. Highest callus induction (76.4–84.3%) was obtained in five treatments containing 2,4-Dichlorophenoxyacetic acid (2,4-d: 0.45–9.05 μM) with Kinetin (KIN: 2.32, 4.65 μM), whereas highest root induction (79.6%) corresponded to the α-Naphthaleneacetic acid (9.05 μM) with KIN (2.32 μM) treatment. Verbascoside was the major phenylpropanoid produced in in vitro cultures (root, white and green callus) [66.24–86.26 mg g⁻¹ dry weight (DW)], while linarin and hydroxycinnamic acid production was low (0.95–3.01 mg g⁻¹ DW). Verbascoside and linarin production were improved in cell suspension culture (116 mg g⁻¹ DW and 8.12 mg g⁻¹ DW, respectively).     

Primary production in papyrus (<Emphasis Type="Italic">Cyperus papyrus</Emphasis> L.) of Rubondo Island,Lake Victoria,Tanzania

Above- and below-ground production and morphological characteristics of papyrus wetlands were measured at monthly intervals from July 2005 to June 2006 at Rubondo Island, Lake Victoria, Tanzania. The average value of live culm biomass (5,789 ± 435 g DW m⁻²) was higher than that of umbel biomass (2,902 ± 327 g DW m⁻²) by 50%. Root to rhizome means biomass value ratio was 1:1.8, rhizome biomass (4,144 ± 452 g DW m⁻²) being higher than roots biomass (2,254 ± 314 g DW m⁻²) by 45%. Direct proportion was observed between shoot density and culm–unit (culms and umbels) biomass. The average value of detritus/litter biomass (1,306 ± 315 g DW m⁻²) was less than total aerial biomass by 86%. The values of biomass are average of 12 sampling months from July 2005 to June 2006.     

Maximum Photosynthetic Yield of Green Microalgae in Photobioreactors

The biomass yield on light energy of Dunaliella tertiolecta and Chlorella sorokiniana was investigated in a 1.25- and 2.15-cm light path panel photobioreactor at constant ingoing photon flux density (930 μmol photons m⁻² s⁻¹). At the optimal combination of biomass density and dilution rate, equal biomass yields on light energy were observed for both light paths for both microalgae. The observed biomass yield on light energy appeared to be based on a constant intrinsic biomass yield and a constant maintenance energy requirement per gram biomass. Using the model of Pirt (New Phytol 102:3–37, 1986), a biomass yield on light energy of 0.78 and 0.75 g mol photons⁻¹ and a maintenance requirement of 0.0133 and 0.0068 mol photons g⁻¹ h⁻¹ were found for D. tertiolecta and C. sorokiniana, respectively. The observed yield decreases steeply at low light supply rates, and according to this model, this is related to the increase of the amount of useable light energy diverted to biomass maintenance. With this study, we demonstrated that the observed biomass yield on light in short light path bioreactors at high biomass densities decreases because maintenance requirements are relatively high at these conditions. All our experimental data for the two strains tested could be described by the physiological models of Pirt (New Phytol 102:3–37, 1986). Consequently, for the design of a photobioreactor, we should maintain a relatively high specific light supply rate. A process with high biomass densities and high yields at high light intensities can only be obtained in short light path photobioreactors.     

Two-stage culture for producing berberine by cell suspension and shoot cultures of <Emphasis Type="Italic">Berberis buxifolia</Emphasis> Lam

In vitro cultures of Berberis buxifolia were established using thidiazuron (4.5, 23 and 45 mM) or picloram (4 and 40 mM) as plant growth regulators for sustaining growth. For producing berberine, a two-stage culture was performed. In the first step, thidiazuron or picloram were used for biomass production followed by the production stage where benzylaminopurine (4.4 mM) was added as a plant growth regulator. Berberine yields (102 mg g⁻¹ DW) and in vitro shoot cultures (200 mg g⁻¹ DW) were significantly lower than those of whole plants in the field (416 mg g⁻¹ DW). The highest productivity (0.18 mg 1⁻¹ day⁻¹) was attained using picloram (either 4 on 40 mM) in the first stage for producing biomass.     

Soil algal communities inhabiting zinc and lead mine spoils

Algal communities inhabiting four calamine mine spoils differing in time since cessation of exploitation and loaded with high concentrations of zinc (20,284–61,599 μg g⁻¹ soil DW), lead (2,620–3,885 μg g⁻¹ DW) and cadmium (104–232 μg g⁻¹ DW) were studied. In dump soils of slightly alkaline pH (7.28–7.52) and low nutrient (, , ) concentrations, chlorophyll a content ranged from 0.41 to 2.27 μg g⁻¹ soil DW. In total, 23 algal species were recorded. Chlorophyta were the dominant taxonomic group (42–55% of all identified species) followed by Cyanobacteria (28–36%) and Heterokontophyta (13–21%). The highest species richness (18) was observed in the oldest dump (120 years old) with natural succession, while in younger dumps it was lower (11–15). Total algal abundance ranged between 5.5 and 19.1 × 10² ind. g⁻¹ soil DW, and values of Margalef’s diversity indices (1.59–2.25) were low. These results may suggest that both high concentrations of heavy metals and low nutrient content influenced the algal communities in all the dumps studied. The differences in algal microflora observed between tailing dumps may indicate that habitat quality improved with time and that algae isolated from Zn/Pb-loaded soils may be Zn/Pb-resistant ecotypes of ubiquitous species.     

Inoculum size and auxin concentration influence the growth of adventitious roots and accumulation of ginsenosides in suspension cultures of ginseng ( Panax ginseng C.A. Meyer)

The effect of the root-inoculum size and axuin concentration on growth of adventitious roots and accumulation of ginsenosides were studied during suspension cultures of ginseng (Panax ginseng C.A. Meyer). Of the various concentrations of indole-3-butyric acid (IBA) and γ-naphthaleneacetic acid (NAA) used as supplementary growth regulators along with Murashige and Skoog medium, 25 μM IBA was found suitable for lateral root induction and growth, as well as accumulation of ginsenosides. Inoculum size of 5 g L⁻¹ was found suitable for optimal biomass (10.5 g L⁻¹ dry biomass) and ginsenosides (5.4 mg g⁻¹ DW) accumulation. Of the various length of root inocula tested (chopped to 1–3, 4–6, 7–10 mm and un-chopped), root inocula of 7–10 mm was found suitable for biomass and ginsenoside accumulation.     

Effects of aeration intensity on formation of phenol-fed aerobic granules and extracellular polymeric substances

Effect of air aeration intensities on granule formation and extracellular polymeric substances content in three identical sequential batch reactors were investigated. The excitation–emission–matrix spectra and multiple staining and confocal laser scanning microscope revealed proteins, polysaccharides, lipids, and humic substances in the sludge and granule samples. Seed sludge flocs were compacted at low aeration rate, with produced extracellular polymeric substances of 50.2–76.7 mg g⁻¹ of proteins, 50.2–77.3 mg g⁻¹ carbohydrates and 74 mg g⁻¹ humic substances. High aeration rate accelerated formation of 1.0–1.5 mm granules with smooth outer surface. The corresponding quantities of extracellular polymeric substances were 309–537 mg g⁻¹ of proteins, 61–109 mg g⁻¹ carbohydrates, 49–92 mg g⁻¹ humic substances, and 49–68 mg g⁻¹ lipids. Intermediate aeration rate produced 3.0–3.5 mm granules with surface filaments. Reactor failure occurred with overgrowth of filaments, probably owing to the deficiency of nutrient in liquid phase. No correlation was noted between extracellular polymeric substances composition and the proliferation of filamentous microorganisms on granule surface.     

Zooplankton biomass in tropical reservoirs in southern Brazil

In order to test the hypothesis that zooplankton biomass distribution (total and taxonomic groups) was influenced by the nutrient concentration and primary productivity distribution in three tropical reservoirs, subsurface samples were taken in the fluvial, transitional and lacustrine regions of three reservoirs (oligotrophic, mesotrophic and eutrophic) in southern Brazil (Paraná State) in March and September 2002. Zooplankton biomass ranged from 0.04 to 264.47 mg DW m⁻³. Higher biomass values were observed for cladocerans (73.60%; 0.01–259.86 mg DW m⁻³), followed by copepods (22.05%; 0.01–69.69 mg DW m⁻³) and rotifers (4.35%; 0.01–11.52 mg DW m⁻³). In general, the total zooplankton, rotifer, cladoceran and copepod biomass, and chlorophyll-a and total nutrient concentrations showed a similar longitudinal distribution within the reservoirs. Total zooplankton, rotifer and cladoceran biomass were related to the chlorophyll-a concentration, and zooplankton biomass was related to the total phosphorus distribution. This may have been due to the significant multicolinearity between the chlorophyll-a and total phosphorus concentrations. Cyanobacteria influenced the taxonomic group biomass results by interfering with the filter feeding in larger zooplankton species, which favoured the dominance of smaller species. As regards the longitudinal distribution of copepod biomass, cyanobacteria biomass determined the displacement of the microcrustaceans to the fluvial region of Iraí Reservoir. Our results supported the hypothesis formulated and the primary productivity was the major predictor of the zooplankton biomass distribution in the reservoirs. Handling editor: S. Dodson     

Nutrient content of tropical edible seaweeds, Eucheuma cottonii, Caulerpa lentillifera and Sargassum polycystum

The proximate composition, vitamin C, α-tocopherol, dietary fibers, minerals, fatty acid and amino acid profiles of three tropical edible seaweeds, Eucheuma cottonii (Rhodophyta), Caulerpa lentillifera (Chlorophyta) and Sargassum polycystum (Phaeophyta) were studied. The seaweeds were high in ash (37.15–46.19%) and dietary fibers (25.05–39.67%) and low in lipid content (0.29–1.11%) on dry weight (DW) basis. These seaweeds contained 12.01–15.53% macro-minerals (Na, K, Ca and Mg) and 7.53–71.53 mg.100 g⁻¹ trace minerals (Fe, Zn, Cu, Se and I). The crude protein content of E. cottonii (9.76% DW) and C. lentillifera (10.41% DW) were higher than that of S. polycystum (5.4% DW), and protein chemical scores are between 20 and 67%. The PUFA content of E. cottonii was 51.55%, C. lentillifera 16.76% and S. polycystum 20.34%. Eicosapentaenoic acid (EPA), accounted for 24.98% of all fatty acids in E. cottonii. These seaweeds have significant vitamin C (∼35 mg.100 g⁻¹) and α-tocopherol (5.85–11.29 mg.100 g⁻¹) contents.     

The shikonin derivatives and pyrrolizidine alkaloids in hairy root cultures of Lithospermum canescens (Michx.) Lehm.

Hairy root cultures of Lithospermum canescens were established using three strains of Agrobacterium rhizogenes: ATCC 15834, LBA 9402 and NCIB 8196. Eight lines resulting from infection with A. rhizogenes ATCC 15834 demonstrated sufficient biomass increase and were submitted to further investigations. The contents of acetylshikonin (ACS) and isobutyrylshikonin (IBS) in transformed hairy roots made up ca. 10% of those observed in natural roots of L. canescens (24.35 and 14.48 mg g⁻¹ DW, respectively). One line, Lc1-D, produced the largest amounts of ACS (2.72 mg g⁻¹ DW) and IBS (0.307 mg g⁻¹ DW). Traces of pyrrolizidine alkaloids (PA), canescine and canescenine, were found in all lines of transformed hairy roots.     

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.     

Spatial and Temporal Variability in Sediment Denitrification Within an Agriculturally Influenced Reservoir

Reservoirs are intrinsically linked to the rivers that feed them, creating a river–reservoir continuum in which water and sediment inputs are a function of the surrounding watershed land use. We examined the spatial and temporal variability of sediment denitrification rates by sampling longitudinally along an agriculturally influenced river–reservoir continuum monthly for 13 months. Sediment denitrification rates ranged from 0 to 63 μg N₂O g ash free dry mass of sediments (AFDM)⁻¹ h⁻¹ or 0–2.7 μg N₂O g dry mass of sediments (DM)⁻¹ h⁻¹ at reservoir sites, vs. 0–12 μg N₂O gAFDM⁻¹ h⁻¹ or 0–0.27 μg N₂O gDM⁻¹ h⁻¹ at riverine sites. Temporally, highest denitrification activity traveled through the reservoir from upper reservoir sites to the dam, following the load of high nitrate (NO₃⁻-N) water associated with spring runoff. Annual mean sediment denitrification rates at different reservoir sites were consistently higher than at riverine sites, yet significant relationships among theses sites differed when denitrification rates were expressed per gDM vs. per gAFDM. There was a significant positive relationship between sediment denitrification rates and NO₃⁻-N concentration up to a threshold of 0.88 mg NO₃⁻ -N l⁻¹, above which it appeared NO₃⁻-N was no longer limiting. Denitrification assays were amended seasonally with NO₃⁻-N and an organic carbon source (glucose) to determine nutrient limitation of sediment denitrification. While organic carbon never limited sediment denitrification, all sites were significantly limited by NO₃⁻-N during fall and winter when ambient NO ₃⁻-N was low.     

Different nutrient use strategies of expansive grasses <Emphasis Type="Italic">Calamagrostis epigejos</Emphasis> and <Emphasis Type="Italic">Arrhenatherum elatius</Emphasis>

Enhanced nitrogen (N) levels accelerate expansion of Calamagrostis epigejos and Arrhenatherum elatius, highly aggressive expanders displacing original dry acidophilous grassland vegetation in the Podyjí National Park (Czech Republic). We compared the capability of Calamagrostis and Arrhenatherum under control and N enhanced treatments to (i) accumulate N and phosphorus (P) in plant tissues, (ii) remove N and P from above-ground biomass during senescence and (iii) release N and P from plant material during decomposition of fresh formed litter. In control treatment, significantly higher amounts of total biomass and fresh aboveground litter were observed in Calamagrostis than in Arrhenatherum. Contrariwise, nutrient concentrations were significantly higher (11.6–14.3 mg N g⁻¹ and 2.3 mg P g⁻¹) in Arrhenatherum peak aboveground biomass than in Calamagrostis (8.4–10.3 mg N g⁻¹ and 1.6–1.7 mg P g⁻¹). Substantial differences between species were found in resorption of nutrients, mainly P, at the ends of growing seasons. While P concentrations in Arrhenatherum fresh litter were twice and three times higher (1.6–2.5 mg P g⁻¹) than in Calamagrostis (0.7–0.8 mg P g⁻¹), N concentrations were nearly doubled in Arrhenatherum (13.1–15.6 mg N g⁻¹) in comparison with Calamagrostis (7.4–8.7 mg N g⁻¹). Thus, the nutrients (N and mainly P) were retranslocated from the aboveground biomass of Calamagrostis probably more effectively in comparison with Arrhenatherum at the end of the growing season. On the other hand, Arrhenatherum litter was decomposed faster and consequently nutrient release (mainly N and P) was higher in comparison with Calamagrostis which pointed to different growth and nutrient use strategies of studied grass species.     

Bioreactor application on adventitious root culture of <Emphasis Type="Italic">Astragalus membranaceus</Emphasis>

Astragalus membranaceus is one of the most widely used traditional medicinal herbs in China, but the time required to generate a useful product in the field production is long. The growth of adventitious root cultures was compared between cultures grown in solid, liquid, or a 5-L balloon-type bubble bioreactor. The maximum growth ratio (final dry weight/initial dry weight) was determined for adventitious roots grown in the bioreactor. Studies carried out to optimize biomass production of adventitious roots compared adventitious root growth from various inoculum root lengths, inoculum densities, and aeration volume in the bioreactors. The maximum growth ratio occurred in treatments with a 1.5-cm inoculum root length, with 30 g (fresh weight) of inoculum per bioreactor or with an aeration volume of 0.1 vvm (air volume/culture medium volume per min). The polysaccharide, saponin, and flavonoid content of roots from bioreactor-grown cultures were compared to roots from field-grown plants grown for 1 and 3 yr. Total polysaccharide content of adventitious roots in the bioreactor (30.0 mg g⁻¹ dry weight (DW)) was higher than the roots of 1-yr-old (13.8 mg g⁻¹ DW) and 3-yr-old (21.1 mg g⁻¹ DW) plants in the field. Total saponin (3.4 mg g⁻¹ DW) and flavonoid (6.4 mg g⁻¹ DW) contents were nearly identical to 3-yr-old roots and higher than that of 1-yr-old roots under field cultivation.     

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.