The influence of size on domoic acid concentration in king scallop, Pecten maximus (L.)

Concentrations of domoic acid (DA), the biotoxin responsible for amnesic shellfish poisoning (ASP), exceeding the regulatory limit of 20 μg g⁻¹ have caused restricted harvesting and closures of wild king scallop fisheries. Toxin monitoring programmes have reported significant inter-animal variation in DA concentration between scallops from the same area. For the development of reliable sampling and management protocols an understanding of the magnitude and causes of inter-animal variation in toxin concentration are important. Ten samples were collected from an aquaculture site in Clew Bay, Co. Mayo off the west coast of Ireland between February 2003 and February 2004, each sample comprising 12 scallops of each of the following size groups: small (70–85 mm), medium (85–100 mm), large (100–115 mm) and very large (>115 mm). DA concentration in each hepatopancreas and in composite samples of both gonad and adductor muscle from each size group on each sampling occasion were measured. High inter-animal variability in DA concentration in hepatopancreas was recorded; CVs ranging from 12.5% to 82.5%. One negative correlation (R² = 0.7079) between DA concentration in hepatopancreas and scallop shell length, three positive but weak correlations (R² = 0.4536, 0.3459 and 0.4665) and six no correlations were exhibited. Negative correlations were attributed to faster DA uptake by smaller scallops, positive correlations to faster DA depuration by smaller scallops. If only scallops greater than or equal to 100 mm shell length, the minimum commercial size of this species were considered, no correlation occurred on any of the 10 sampling occasions.     

Spatial variability of domoic acid concentration in king scallops Pecten maximus off the southeast coast of Ireland

Amnesic shellfish poisoning (ASP) has proved problematic in Irish king scallop, Pecten maximus fisheries necessitating restrictions on the sale of fresh scallops (in-shell), which achieve a higher market price than frozen processed product. An investigation of variability in domoic acid (DA) concentration in king scallop from 69 sampling sites within a limited area off the southeast coast of Ireland was performed. Variation in DA concentration was examined in the whole area, within smaller sub-areas, with size, age, and water depth. Mean DA concentrations in whole scallop ranged from 6.5 to 154.3 μg g⁻¹, with an overall mean of 40.6 ± 30.8 μg g⁻¹. The concentration in gonad exceeded 20 μg g⁻¹ in 17 sites and in adductor muscle in 3 sites. Significant differences in DA concentration were detected between scallops from different sampling stations. Whole scallop tissue and individual scallop tissues with the exception of gonad, exhibited significant negative correlations with water depth. Highest DA concentrations were recorded in inshore, shallow sites and lowest DA concentrations in deeper offshore waters. Significant positive correlations between DA concentration in hepatopancreas and scallop size were exhibited at inshore sites but not at offshore sites. High inter-animal and spatial variability in toxin concentration demonstrated the importance of a reliable sampling protocol for the management of ASP outbreaks to ensure public safety and to avoid unnecessary fishery closures.     

Effect of storage on amnesic shellfish poisoning (ASP) toxins in king scallops (Pecten maximus)

Since 1998, king scallops (Pecten maximus) obtained from Scottish offshore sites have been monitored for domoic acid (DA) and epi-domoic acid (epi-DA), the principal toxic compounds associated with amnesic shellfish poisoning (ASP). The presence of these toxins in king scallops harvested from Scottish waters at concentrations exceeding the current regulatory limit (20 μg g⁻¹ shellfish flesh) is a recurrent event. However, little information was available to determine the effects that different storage conditions experienced during sample transportation to the monitoring laboratory may have on the toxin concentrations, which are subsequently detected. Furthermore, the stability of DA and epi-DA in the solvents (methanol:water (1:1, v/v) and citric acid buffer (0.5 M, pH 3.2)) routinely used for their extraction from shellfish has not previously been assessed. Results from this study demonstrate that when king scallop samples were stored for 2–3 days at 12 °C, a significantly higher toxin concentration was detected in the gonad than when samples were stored at 4 °C and analysed within 48 h. This implies that monitoring programmes must consider transport and storage conditions between harvest and analysis. Stability studies showed rapid decomposition of DA and epi-DA in aqueous methanol extracts while DA and epi-DA seem acceptably stable when stored refrigerated in citrate buffer.     

Impact of preparation method on gonad domoic acid levels in the scallop, Pecten maximus (L.)

The king scallop, Pecten maximus (L.), fishery is a valuable economic resource in the UK, and is reliant on supplying premium “roe-on” processed scallops to the continental market. A considerable degree of variability is observed in domoic acid (DA) levels among individual P. maximus and their body components, which complicates the management of the fishery during amnesic shellfish poisoning (ASP) events. This study examined the impact of professional processing and three differing laboratory preparation techniques on final gonadal DA levels. DA analysis was conducted using a LC–MS/MS procedure. The results demonstrate that different methods of preparation can significantly alter gonadal toxicities in scallops from the same site, and the extent to which DA within the digestive loop, which passes through the gonad, contributes to total gonadal DA. Mean gonadal toxicity attributed to the digestive loop contents was estimated at 4.7–24.7 μg DA g⁻¹. Despite large individual variations in toxin levels; in scallops with elevated gonadal toxicities resulting from higher digestive loop content toxicity, the effect of flushing out the contents of the digestive loop significantly reduced the DA content of the tissue and lowered the frequency of individuals harbouring levels above the 20 μg DA g⁻¹ statutory safety limit. Removal of the digestive loop contents can potentially result in an 87% decrease in gonadal DA burden. Furthermore, the method applied by professional processors effectively removed the contents of the digestive loop and reduced gonadal DA to levels comparable with the laboratory techniques. Deliberate contamination with scallop mucus did not increase gonadal DA levels. The extent of toxin variation resulting from differing gonad preparations demonstrates the need to standardize scallop tissue preparation techniques during ASP events. Consequently, detailed protocols aimed at minimizing the contamination of edible components should be developed and adhered to by both processing facilities and monitoring bodies.     

Paralytic shellfish toxins in zooplankton, mussels, lobsters and caged Atlantic salmon, Salmo salar, during a bloom of Alexandrium fundyense off Grand Manan Island, in the Bay of Fundy

Substantial mortalities of Atlantic salmon (Salmo salar) at two aquaculture sites in Long Island Sound, off Grand Manan Island, Bay of Fundy (BoF) (New Brunswick, Canada) in September 2003, were associated with a bloom of Alexandrium fundyense (>3 × 10⁵ cells L⁻¹), a dinoflagellate alga that produces toxins which cause paralytic shellfish poisoning (PSP). Cells of A. fundyense collected from surface waters while fish were dying had total paralytic shellfish (PS) toxin concentrations of 70.6 pg STX equiv. (saxitoxin equivalents) cell⁻¹ and PS toxin profiles rich in carbamate toxins (78.2%). The zooplankton sampled contained PS toxins (63.1 pg STX equiv. g⁻¹ wet wt) and the toxin profile matched that of A. fundyense cells.Mean PS toxin levels were low (<4 μg STX equiv. 100 g⁻¹ wet wt) in stomach, gill and muscle tissues of moribund salmon, suggesting that PS toxins are very lethal to salmon.The PS toxin concentrations in blue mussels (Mytilus edulis) growing on the salmon cages (37; 526 μg STX equiv. 100 g⁻¹ wet wt) were the highest recorded to date from this region. Their PS toxin profiles showed enhanced carbamate contents (85.5%) compared with that found in A. fundyense. Blue mussels collected from an adjacent Canadian Food Inspection Agency (CFIA) monitoring site in Grand Manan had PS toxin concentrations of 4214 and 150 μg STX equiv. 100 g⁻¹ wet wt in late September and December, respectively, well above the regulatory limit (RL), and horse mussels (Modiolus modiolus) collected in late September had PS toxin concentrations of 2357 μg STX equiv. 100 g⁻¹ wet wt. Detoxification under laboratory conditions suggested that blue mussels may require up to 19 weeks for elimination below RL when they accumulate these high concentrations of PS toxins. This depuration period may be shorter in the field.PS toxin levels above RL were detected in hepatopancreatic tissues of lobster (Homarus americanus), with lower levels (<16 μg STX equiv. 100 g⁻¹ wet wt) in tail muscle and gills.These results illustrate the movement of PS toxins through the marine food chain following an A. fundyense bloom in the BoF, and support earlier studies suggesting that kills from the region of zooplanktivorous fish, such as herring (Clupea harengus harengus), can be attributed to blooms of A. fundyense. This is the first reported incident of PSP associated with mortalities of caged Atlantic salmon in the BoF. Analyses of muscle tissues and viscera from the affected salmon indicated that any portion would not be a health hazard if consumed.     

Does uptake of Alexandrium fundyense cysts contribute to the levels of PSP toxin found in the sea scallop, Placopecten magellanicus?

Atlantic sea scallops, Placopecten magellanicus, in most areas of the Bay of Fundy, New Brunswick, Canada, have year-round concentrations of paralytic shellfish posioning (PSP) toxins greater than the regulatory concentration of 80 μg STX eq. 100 g⁻¹ wet weight. Scallops (mean shell height of 10.7 cm, age 3–5 years) were collected by SCUBA and individually tagged near Parker Island, Bay of Fundy. Half were hung 2 m below the low tide water level and the remainder were placed on the bottom (11 m depth at low tide) under the scallops held at 2 m. Scallop, water and sediment samples were collected monthly for determination of concentrations of PSP toxins and Alexandrium fundyense.In October, 1993, mean concentrations of PSP toxins in digestive gland, and mantle were 3205 and 1018 μg STX eq. 100 g⁻¹ wet weight, respectively. Eight months later (June 1994), PSP concentrations in digestive glands from the surface and bottom had declined to 504 and 682 μg STX eq. 100 g⁻¹ wet weight, respectively, whereas those in the mantle had declined to 802 and 681 μg STX eq. 100 g⁻¹ wet weight. During July 1994, A. fundyense concentrations observed at Parker Island and offshore were 320 cells l⁻¹ and 14,200 cells l⁻¹, respectively. Subsequently, toxin concentrations in surface and bottom scallop digestive glands increased to 12,720 and 11,408 μg STX eq. 100 g⁻¹ wet weight, whereas concentrations in mantles increased to 2126 and 1748 μg STX eq. 100 g⁻¹ wet weight, respectively. Concentrations of PSP toxins in these tissues in October 1994 were similar to those measured in October 1993. Concentrations of PSP toxin were less than the regulatory concentration in the gonads and non-detectable in adductor muscles of all scallops sampled.There were no statistically significant differences in profiles for uptake and depuration of PSP toxins in scallops held at the surface compared to those from bottom, suggesting that A. fundyense cysts at the concentrations found in the sediment (45 cysts cm⁻³) did not contribute significantly to the year-round presence of PSP toxins within scallop tissues. The year-round occurrence of PSP toxin is probably due to accumulation during summer blooms followed by a very slow rate of depuration.     

Blooms of Pseudo-nitzschia and domoic acid in the San Pedro Channel and Los Angeles harbor areas of the Southern California Bight, 2003–2004

Abundances of Pseudo-nitzschia spp. and concentrations of particulate domoic acid (DA) were determined in the Southern California Bight (SCB) along the coasts of Los Angeles and Orange Counties during spring and summer of 2003 and 2004. At least 1500 km² were affected by a toxic event in May/June of 2003 when some of the highest particulate DA concentrations reported for US coastal waters were measured inside the Los Angeles harbor (12.7 μg DA L⁻¹). Particulate DA levels were an order of magnitude lower in spring of 2004 (February and March), but DA concentrations per cell at several sampling stations during 2004 exceeded previously reported maxima for natural populations of Pseudo-nitzschia (mean = 24 pg DA cell⁻¹, range = 0–117 pg DA cell⁻¹). Pseudo-nitzschia australis dominated the Pseudo-nitzschia assemblage in spring 2004. Overall, DA-poisoning was implicated in >1400 mammal stranding incidents within the SCB during 2003 and 2004. Ancillary physical and chemical data obtained during our regional surveys in 2004 revealed that Pseudo-nitzschia abundances, particulate DA and cellular DA concentrations were inversely correlated with concentrations of silicic acid, nitrogen and phosphate, and to specific nutrient ratios. Particulate DA was detected in sediment traps deployed at 550 and 800 m depth during spring of 2004 (0.29–7.6 μg DA (g sediment dry weight)⁻¹). The highest DA concentration in the traps was measured within 1 week of dramatic decreases in the abundances of Pseudo-nitzschia in surface waters. To our knowledge these are the deepest sediment trap collections from which DA has been detected. Sinking of the spring Pseudo-nitzschia bloom may constitute a potentially important link between DA production in surface waters and benthic communities in the coastal ocean near Los Angeles. Our study indicates that toxic blooms of Pseudo-nitzschia are a recurring phenomenon along one of the most densely populated coastal stretches of the SCB and that the severity and magnitude of these events can be comparable to or greater than these events in other geographical regions affected by domoic acid.     

Cyanobacteria and cyanobacterial toxins in the alkaline crater lakes Sonachi and Simbi, Kenya

The phytoplankton communities and the production of cyanobacterial toxins were investigated in two alkaline Kenyan crater lakes, Lake Sonachi and Lake Simbi. Lake Sonachi was mainly dominated by the cyanobacterium Arthrospira fusiformis, Lake Simbi by A. fusiformis and Anabaenopsis abijatae. The phytoplankton biomasses measured were high, reaching up to 3159 mg l⁻¹ in L. Sonachi and up to 348 mg l⁻¹ in L. Simbi. Using HPLC techniques, one structural variant of the hepatotoxin microcystin (microcystin-RR) was found in L. Sonachi and four variants (microcystin-LR, -RR, -LA and -YR) were identified in L. Simbi. The neurotoxin anatoxin-a was found in both lakes. To our knowledge this is the first evidence of cyanobacterial toxins in L. Sonachi and L. Simbi. Total microcystin concentrations varied from 1.6 to 12.0 μg microcystin-LR equivalents g⁻¹ DW in L. Sonachi and from 19.7 to 39.0 μg microcystin-LR equivalents g⁻¹ DW in L. Simbi. Anatoxin-a concentrations ranged from 0.5 to 2.0 μg g⁻¹ DW in L. Sonachi and from 0 to 1.4 μg g⁻¹ DW in L. Simbi. In a monocyanobacterial strain of A. fusiformis, isolated from L. Sonachi, microcystin-YR and anatoxin-a were produced. The concentrations found were 2.2 μg microcystin g⁻¹ DW and 0.3 μg anatoxin-a g⁻¹ DW. This is the first study showing A. fusiformis as producer of microcystins and anatoxin-a. Since A. fusiformis occurs in mass developments in both lakes, a health risk for wildlife can be expected.     

Reduction of cyanobacterial toxins through coprophagy in Mytilus edulis

An experiment was conducted to follow the fate of the cyanobacterial toxin, nodularin, produced by Nodularia spumigena through ingestion by Mytilus edulis and re-ingestion of faecal material (coprophagy). Mussels were fed with cultures of N. spumigena, and the faeces that were produced were fed to other mussels not previously exposed to N. spumigena. Concentrations of nodularin were measured in the food (N. spumigena), the mussels and in the faeces in order to make a toxin budget. High concentrations of nodularin were found in the mussels and their faeces after 48 h incubation with N. spumigena. When the toxic faeces were fed to new mussels, the toxin content of faeces was reduced from 95 μg nod g⁻¹ dry weight (DW) to 1 μg nod g⁻¹ DW through the process of coprophagy. Hence, when toxic faeces were fed to mussels, the nodularin concentration of the resulting faecal material was reduced by 99%. Pseudofaeces were produced when the mussels were grazing on N. spumigena, but not when grazing on faeces. The pseudofaeces contained high concentrations of nodularin and apparently intact N. spumigena cells. However, these cells were growth-inhibited and their potential contribution to seeding a bloom is probably limited. Our data indicate that a large fraction of ingested nodularin in M. edulis is egested with the faeces, and that the concentration of nodularin in the faeces is reduced when faeces are re-ingested.     

Ergosterol contents of some wood-rotting basidiomycete fungi grown in liquid and solid culture conditions

Ergosterol contents of six wood-rotting basidiomycetes were analyzed under different cultivation conditions. Four white-rot and two brown-rot fungi were cultivated in liquid synthetic medium with low nutrient nitrogen (2 mM) and 0.1% glucose, and ergosterol in mycelial biomasses were measured weekly for 35 days. The highest ergosterol content per fungal dry mass in the white-rot fungi was found in Phanerochaete chrysosporium being 2100 μg g⁻¹, while in Ceriporiopsis subvermispora it was 1700 μg g⁻¹, Phlebia radiata 700 μg g⁻¹, and Physisporinus rivulosus 560 μg g⁻¹. In brown-rot fungi the ergosterol content was in Poria placenta 2868 μg g⁻¹ and in Gloeophyllum trabeum 3915 μg g⁻¹. On agar media, P. chrysosporium and P. radiata reached the highest ergosterol value in 7 days, while in wood block cultures the ergosterol contents were quite stable. The conversion factors for ergosterol-to-fungal biomass varied from 48 and 243, which were lower than values for ascomycetous soil fungi reported in the literature.     

Comparison on the removal of phthalic acid diesters in a bioreactor landfill and a conventional landfill

The removal of phthalic acid diesters (PAEs) in municipal solid waste (MSW) from two simulated landfill reactors was compared. The results showed that the original concentrations of dimethyl phthalate (DMP), dibutyl phthalate (DBP) and dioctyl phthalate (DOP) in the refuse were 3.3 μg g⁻¹, 18.5 μg g⁻¹ and 0.8 μg g⁻¹, respectively. The concentrations of DMP and DBP in both leachate and refuse decreased greatly during decomposition of the waste in both reactors. The major loss of PAEs from the landfill occurred during an active methanogenic environment with a low concentration of volatile fatty acids (VFA) in the later period. In addition, strong correlations were found between the residual DMP, DBP concentrations and the biologically degradable material (BDM) of the refuse. Finally, PAEs degraded more rapidly in the landfill that was operated in conjunction with the methanogenic reactor when compared to the landfill with direct leachate discharge.     

Note on the occurrence of Pseudo-nitzschia australis and domoic acid in squid from Monterey Bay, CA (USA)

Over the past decade diatom blooms of domoic acid (DA)-producing Pseudo-nitzschia spp. have been responsible for numerous marine mammal and bird mortalities in Monterey Bay, CA. One possible toxin vector is the market squid, Loligo opalescens, a small pelagic mollusk that plays an important role in the near-shore food web of the California Current ecosystem as a favored vertebrate prey species. This study examined the trophic link between toxic Pseudo-nitzschia and L. opalescens using toxin and stomach content analyses of animals collected from Monterey Bay, CA in 2000. Receptor binding assay data (confirmed by tandem mass spectrometry), demonstrated the presence of DA in squid during a toxic Pseudo-nitzschia event, with P. australis frustules observed in stomach samples. Though DA levels were low (<0.5 μg DA g⁻¹ tissue) in L. opalescens during the study period, it is now clear that this potent neurotoxin can occur in squid and is likely delivered through its krill prey species, which are known to retain DA after feeding on toxic Pseudo-nitzschia. Our findings suggest that further study of the relationship between Pseudo-nitzschia blooms and DA contamination of squid is warranted to better evaluate the potential health risk to humans and wildlife associated with this major commercial seafood species and important prey item.     

Enhanced yield of medium-chain-length polyhydroxyalkanoates from nonanoic acid by co-feeding glucose in carbon-limited, fed-batch culture

Medium-chain-length polyhydroxyalkanoates (MCL-PHAs) were produced in carbon-limited, single-stage, fed-batch fermentations of Pseudomonas putida KT2440 by co-feeding nonanoic acid (NA) and glucose (G) to enhance the yield of PHA from NA. An exponential (μ = 0.25 h⁻¹) followed by a linear feeding strategy at a NA:G ratio of 1:1 (w/w) achieved 71 g l⁻¹ biomass containing 56% PHA. Although the same overall PHA productivity (1.44 g l⁻¹ h⁻¹) was obtained when NA alone was fed at the same specific growth rate, the overall yield of PHA from NA increased by 25% (0.66 g PHA g NA⁻¹ versus 0.53 g g⁻¹) with glucose co-feeding. Further increasing glucose in the feed (NA:G = 1:1.5) resulted in a slightly higher yield (0.69 g PHA g NA⁻¹) but lower PHA content (48%) and productivity (1.16 g l⁻¹ h⁻¹). There was very little change in the PHA composition.     

Nitrogenous preference of toxigenic Pseudo-nitzschia australis (Bacillariophyceae) from field and laboratory experiments

Field and laboratory experiments were designed to determine the differential growth and toxin response to inorganic and organic nitrogen additions in Pseudo-nitzschia spp. Nitrogen enrichments of 50 μM nitrate (KNO₃), 10 μM ammonium (NH₄Cl), 20 μM urea and a control (no addition) were carried out in separate carboys with seawater collected from the mouth of the San Francisco Bay (Bolinas Bay), an area characterized by high concentrations of macronutrients and iron. All treatments showed significant increases in biomass, with chlorophyll a peaking on days 4–5 for all treatments except urea, which maintained exponential growth through the termination of the experiment. Pseudo-nitzschia australis Frenguelli abundance was 10³ cells l⁻¹ at the start of the experiment and increased by an order of magnitude by day 2. Particulate domoic acid (pDA) was initially low but detectable (0.15 μg l⁻¹), and increased throughout exponential and stationary phases across all treatments. At the termination of the experiment, the urea treatment produced more than double the amount of pDA (9.39 μg l⁻¹) than that produced by the nitrate treatment (4.26 μg l⁻¹) and triple that of the control and ammonium treatments (1.36 μg l⁻¹ and 2.64 μg l⁻¹, respectively). The mean specific growth rates, calculated from increases in chlorophyll a and from cellular abundance of P. australis, were statistically similar across all treatments.These field results confirmed laboratory experiments conducted with a P. australis strain isolated from Monterey Bay, CA (isolate AU221-a) grown in artificial seawater enriched with 50 μM nitrate, 50 μM ammonium or 25 μM of urea as the sole nitrogen source. The exponential growth rate of P. australis was significantly slower for cells grown on urea (ca. 0.5 day⁻¹) compared to the cells grown on either nitrate or ammonium (ca. 0.9 day⁻¹). However the urea-grown cells produced more particulate and dissolved domoic acid (DA) than the ammonium- or nitrate-grown cells. The field and laboratory experiments demonstrate that P. australis is able to grow effectively on urea as the primary source of nitrogen and produced more pDA when grown on urea in both natural assemblages and unialgal cultures. These results suggest that the influence of urea from coastal runoff may prove to be more important in the development or maintenance of toxic blooms than previously thought, and that the source of nitrogen may be a determining factor in the relative toxicity of west coast blooms of P. australis.     

Prorocentrum lima (Dinophyceae) in northeastern USA coastal waters: II: Toxin load in the epibiota and in shellfish

The seasonal variation in diarrhetic shellfish poisoning (DSP)-type toxins was followed in the epibiotic community and in shellfish between 41° and 44°N in coastal waters of the northwest Atlantic during a 2-year period. Low levels of okadaic-acid equivalents were detected at all stations in the <90 μm fraction of the collected epibiota as measured by the protein phosphatase inhibition assay, but only 3.5% of the samples had values greater than 100 ng (g dry weight of epibiota)⁻¹. No seasonal pattern could be detected due to differences in intensity, duration and timing of toxin content in the epibiota between the 2 years and between stations. Nevertheless, the concentration of DSP-type toxins in the epibiota correlated weakly but significantly with the abundance of Prorocentrum lima, when data from all stations were considered. A very limited toxin uptake by shellfish was measured at only one station in October and November 2001 and in June and July 2002 at times of maximum cell concentration of P. lima in the epibiota. Toxin levels in shellfish remained well below regulatory limits that would have required quarantine or bans on harvesting. Results from our 2-year survey suggest that, at this time, the threat of DSP events appears minimal. However, the presence of a known toxin producer and its demonstrated ingestion by shellfish would argue for further studies to better understand conditions leading to DSP outbreaks generated by an epiphytic dinoflagellate.     

Enhancement of taxane production in hairy root culture of Taxus x media var. Hicksii

This study assessed the effect of two precursors (l-phenylalanine and p-amino benzoic acid) used alone or in combination with methyl jasmonate, on the growth and accumulation of paclitaxel, baccatin III and 10-deacetylbaccatin III in hairy root cultures of Taxus x media var. Hicksii. The greatest increase in dry biomass was observed after 4 weeks of culturing hairy roots in medium supplemented with 1 μM of l-phenylalanine (6.2 g L⁻¹). Addition of 1 μM of l-phenylalanine to the medium also resulted in the greatest 10-deacetylbaccatin III accumulation (422.7 μg L⁻¹), which was not detected in the untreated control culture. Supplementation with 100 μM of l-phenylalanine together with 100 μM of methyl jasmonate resulted in the enhancement of paclitaxel production from 40.3 μg L⁻¹ (control untreated culture) to 568.2 μg L⁻¹, the highest paclitaxel content detected in the study. The effect of p-amino benzoic acid on taxane production was less pronounced, and the highest yield of paclitaxel (221.8 μg L⁻¹) was observed when the medium was supplemented with 100 μM of the precursor in combination with methyl jasmonate.Baccatin III was not detected under the conditions used in this experiment and the investigated taxanes were not excreted into the medium.     

First evidence for the production of cylindrospermopsin and deoxy-cylindrospermopsin by the freshwater benthic cyanobacterium, Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck

Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck is a common mat-forming benthic cyanobacterium from freshwater habitats. We found that two populations from southeast Queensland (Australia) produce the potent cyanotoxin cylindrospermopsin (CYN) and its analogue, deoxy-cylindrospermopsin (deoxy-CYN). The highest concentrations in environmental samples were 20 and 550 μg g⁻¹ dry weight for CYN and deoxy-CYN, respectively. A sub-sample maintained in culture for over 16 months yielded concentrations of 33 and 308 μg g⁻¹ dry weight for CYN and deoxy-CYN, respectively. The concentration of deoxy-CYN in L. wollei was 10–300 times higher than CYN, suggesting that, unlike many other CYN-producing cyanobacteria, the primary compound produced by L. wollei is deoxy-CYN. The production of CYN and deoxy-CYN by L. wollei represents a potential human health risk and an additional source of these toxins in freshwaters. This is the first report of the production of CYN and deoxy-CYN by L. wollei or any species of the Oscillatoriales.     

Toxicity of Dinophysis spp. in relation to population density and environmental conditions on the Swedish west coast

The aim of this study in the field was to investigate whether there are differences between the outer archipelago (Gullmar Fjord) and a semi-enclosed fjord system (Koljö Fjord) in occurrences of D. acuta and D. acuminata as well as in their content of diarrheic shellfish toxin (DST) per cell. When all data pairs of cell toxicity of D. acuminata and the corresponding number of cells l⁻¹ from the two sites were tested in a regression analysis, a statistically significant negative correlation became evident and was apparent as a straight line on a log–log plot (p < 0.0001). Obviously, there was an overall inverse relationship between the population density of D. acuminata and the toxin content per cell. Plotted on a linear scale, all data-pairs of cell toxicity and cell number made up a parabolic curve. On this curve the data-pairs could be separated into three groups: (i) D. acuminata occurring in numbers of fewer than approximately 100 cells l⁻¹, and with a toxin content per cell above 5 ρg cell⁻¹; (ii) cell numbers between 100 and approximately 250 cells l⁻¹ with a cell toxin content from 5 to 2 ρg cell⁻¹; (iii) when the population became greater than 250 cells l⁻¹, the toxicity, with few exceptions, was less than 2 ρg cell⁻¹. By applying this subdivision, some clear patterns of the distribution of the differently toxic D. acuminata became evident. When comparing the cell toxicity of the two sites, it was obvious that the D. acuminata cells from all depths from the Gullmar Fjord as a mean were significantly more toxic compared to the Koljö Fjord samples. The results have demonstrated that approximately 100 high-toxicity cells in a low-density population at surface may lead to the same accumulation of DST in a mussel as the ingestion of 1500 low-toxicity cells from a high-density pycnocline population.     

Cross-linked enzyme aggregates (CLEAs) with controlled particles: Application to Candida rugosa lipase

Aggregation agent type and concentration, lipase and glutaraldehyde concentration, and pH are able to affect the formation of cross-linked lipase. The carrier-free immobilized Candida rugosa lipase with a particle size of 40–50 μm showed higher activity than that of the lipase with other particle sizes. The carrier-free immobilized C. rugosa lipase can keep 86% original lipase activity (0.018 g g⁻¹ min⁻¹). The enantioselectivity of the carrier-free immobilized lipase (23.3) was about 1.8 times as much as that of the native lipase (13.0) in kinetic resolution of ibuprofen racemic mixture.     

Spread and persistence of a rugulosin-producing endophyte in Picea glauca seedlings

We have studied Picea glauca (white spruce) endophyte colonization and its affect on the growth of Choristoneura fumiferana (spruce budworm). Here we examine the spread and persistence of a rugulosin-producing endophyte and rugulosin in needles from trees maintained in the nursery, as well as in trees planted in a test field site. Additionally, we report toxicity of rugulosin against three P. glauca needle herbivores: C. fumiferana, Lambdina fiscellaria (hemlock looper) and Zeiraphera canadensis (spruce budmoth). Reduction in body weight for both the C. fumiferana and L. fiscellaria were observed at 25 and 50 μm, respectively, and head capsules were reduced at 100 and 150 μm. Z. canadensis larvae did not perform as well in tests due to an Aspergillus fumigatus infection, but were shown to be lighter when tested with 100 and 150 μm compared with controls. The endophyte and its toxin were shown to spread throughout the nursery-grown seedlings. After 3.5 and 4.5 y post-inoculation (one and two years in the test site), the inoculated endophyte and its toxin had remained present with an average rugulosin concentration of 1 μg g⁻¹.