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1.
Cyanobacterial toxin production is allied to some unknown trigger resulting in the production of toxins such as microcystin. We hypothesize that microcystins serve as metal ligands to control bioavailability and toxicity of ambient metals. Since ultraviolet radiation (UVR) promotes photo-oxidation of organic metal ligands and influences trace metal bioavailability, the present study aimed to investigate the influence of UVR, Cu, and Zn on specific growth rates, biomass, photosynthetic capacity, and microcystin content in Microcystis aeruginosa. Two toxigenic strains of Microcystis were cultivated using either Lake Erie filtered water or a chemically defined medium, with realistic concentrations of Cu and Zn combined with natural or artificial UVR exposure. Cu was more toxic than Zn on the basis of free ion concentration of trace metals in synthetic medium, although in Lake Erie water total added Zn (10 nM) or Zn plus Cu (10 nM) had a more detrimental effect on biomass and specific growth rate. Natural UVR delivered at 25% ambient levels caused no decrease on the parameters measured (chlorophyll-a, photosynthetic rate), yet artificial levels of UVR (up to 5.9 μmol UVB photons m−2 s−1) negatively affected biomass and specific growth rate. Cellular levels of microcystin (per unit chlorophyll-a) were concomitant with specific growth rather than being triggered in response either of these stressors (UVR, Zn, and Cu) alone or in combination, in agreement with a purported constitutive production of microcystins.  相似文献   

2.
Water quality experienced changes throughout the 3-year ecological engineering experiment in the drinking water source in Meiliang Bay of Lake Taihu. Average concentrations of TN, TP, NH4+, BOD5 and transparency in the drinking water source during the period of July–December 2005 were 1.85, 0.13, 0.23, 3.03 mg L−1 and 27.5 cm, respectively, decreasing by 47.9%, 21.2%, 83.3%, 54.4% and 24.2%, compared to concentrations from the same period in 2003. Concentrations of chlorophyll a and COD were 89.9 μg L−1 and 6.45 mg L−1, increasing by 27.9% and 17.7%, compared to the values in 2003. Cyanobacteria (mainly Microcystis) dominated the phytoplankton community in the ecological engineering area during July–December 2005. Densities of cyanobacteria and Microcystis were higher in 2005 than in 2004 and higher inside the engineering area than outside. Density percentages of cyanobacteria and Microcystis to total algae were above 90% and 60% during the bloom period. Average density of flagellate algae was higher during July–December 2005 than in 2004. Changes in water quality in the engineering area resulted mainly from the weakening of waves, decrease in concentrations of suspended solids, and assimilation of mass algae and periphytons. In spite of initial improvement of water quality, cyanobacterial bloom still determined the phytoplankton dynamics and variations. Additionally, nutrient concentration still remained at a high level without control of external loading. Therefore, a more holistic approach and long-term management should be adopted in Lake Taihu.  相似文献   

3.
Catches of the economically important Nile tilapia (Oreochromis niloticus L.) from two eutrophic tropical lakes in Uganda, Lake Mburo and Murchison Bay, Lake Victoria, were examined to determine the presence of microcystins (MCs) in gut, liver and muscle of the fish. Analysis for MCs (RR, LR and YR) in both fish and water samples was by liquid chromatography coupled with mass spectroscopy (LC-MS) method. Physico-chemical parameters were also measured to establish the status of both lakes. MC-RR was the most prominent MC detected in Lake Mburo and Murchison Bay samples, there was no evidence of significant seasonal variation in the concentration of MCs in fish tissue. MCs were detected in all water samples from both study lakes. The mean concentration of MCs in water was found higher in dry times for Lake Mburo (P < 0.05) and higher in wet times for Murchison Bay (P < 0.05). MC concentrations in the fish guts were positively related with MC concentrations in water samples from Murchison bay (P < 0.05), no such correlation was found in Lake Mburo. In eutrophic tropical lakes, fish seem to have a high tolerance to the toxicity of cyanotoxins including MCs. However, there is a possibility of accumulating these toxins in their tissue with the threat of transferring them higher up in the food chain. Due to a low sample size and short sampling period, the results can only serve to highlight the potential risk of MC accumulation in Nile tilapia in these lakes. Further studies are needed for the purpose of risk assessment.  相似文献   

4.
Three microalgal species (Dictyosphaerium chlorelloides (D.c.), Scenedesmus intermedius (S.i.) and Scenedesmus sp. (S.s.)) were encapsulated in silicate sol–gel matrices and the increase in the amount of chlorophyll fluorescence signal was used to quantify simazine. Influence of several parameters on the preparation of the sensing layers has been evaluated: effect of pH on sol–gel gelation time; effect of algae density on sensor response; influence of glycerol (%) on the membrane stability. Long term stability was also tested and the fluorescence signal from biosensors remained stable for at least 3 weeks. D.c. biosensor presented the lowest detection limits for simazine (3.6 μg L−1) and the broadest dynamic calibration range (19–860 μg L−1) with IC50 125 ± 14 μg L−1. Biosensor was validated by HPLC with UV/DAD detection. The biosensor showed response to those herbicides that inhibit the photosynthesis at photosystem II (triazines: simazine, atrazine, propazine, terbuthylazine; urea based herbicides: linuron). However, no significant increases of fluorescence response was obtained for similar concentrations of 2,4-D (hormonal herbicide) or Cu(II). The combined use of two biosensors that use two different genotypes, sensitive and resistant to simazine, jointly allowed improving microalgae biosensor specificity.  相似文献   

5.
The development of epilithic cyanobacteria communities in a Mediterranean calcareous stream in the province of Murcia (SE Spain) was studied during the course of one year in an attempt to clarify the environmental variables that influence the production of microcystins. The predominant cyanobacteria were species of Rivularia, which formed conspicuous colonies throughout the year. Seasonally, other species were abundant: Schizothrix fasciculata, Tolypothrix distorta and Phormidium splendidum. All the species collected produced microcystins to a varying degree (up to five varieties), while the benthic community as a whole produced concentrations as high as 20.45 mg m−2. At the same time, the presence of microcystins dissolved in water was confirmed. Among environmental variables, air temperature and silicate content were positively and strongly correlated with total microcystins, while nitrite, nitrate, orthophosphate, calcium and flow were negatively correlated with them. Dissolved microcystins were negatively correlated with microcystin LR, P.A.R. and total phosphorus and positively with rainfall. The production of microcystin YR seems to be regulated by different factors from those regulating the other main varieties (microcystin LR and microcystin RR). The data obtained indicate that all the tested benthic cyanobacteria produced microcystins in this shallow calcareous stream, which may contribute to their predominance in the prevailing conditions. The accumulation of microcystins in mucilaginous colonies of other groups of algae poses new questions concerning the possible ecological function of these compounds and needs further study.  相似文献   

6.
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.  相似文献   

7.
Acid hydrolysis of sugarcane bagasse for lactic acid production   总被引:3,自引:0,他引:3  
In order to use sugarcane bagasse as a substrate for lactic acid production, optimum conditions for acid hydrolysis of the bagasse were investigated. After lignin extraction, the conditions were varied in terms of hydrochloric (HCl) or sulfuric (H2SO4) concentration (0.5–5%, v/v), reaction time (1–5 h) and incubation temperature (90–120 °C). The maximum catalytic efficiency (E) was 10.85 under the conditions of 0.5% of HCl at 100 °C for 5 h, which the main components (in g l−1) in the hydrolysate were glucose, 1.50; xylose, 22.59; arabinose, 1.29; acetic acid, 0.15 and furfural, 1.19. To increase yield of lactic acid production from the hydrolysate by Lactococcus lactis IO-1, the hydrolysate was detoxified through amberlite and supplemented with 7 g l−1 of xylose and 7 g l−1 of yeast extract. The main products (in g l−1) of the fermentation were lactic acid, 10.85; acetic acid, 7.87; formic acid, 6.04 and ethanol, 5.24.  相似文献   

8.
An open tank photobioreactor containing transparent rectangular chambers (TRCs) was developed to improve the photosynthetic efficiency of microalgal cultivation. The TRCs, made of transparent acrylic, conducted light deep into the photobioreactor, especially at high cell concentrations. The average irradiance, Iav, was calculated by Lambert–Beer's law, and was used to determine the light conditions in the cultivation system. The photobioreactor provided large areas of illumination that improved the effective utilization of light energy for microalgae growth and created a good artificial environment for a high rate of cell growth, even at low Iav. The biomass concentration of Chlorella sp. reached 3.745 g L−1 on the 13th day, with biomass productivity of 0.340 g L−1 d−1. The total biomass obtained was 56% more than that of similar culture systems without TRCs.  相似文献   

9.
Kim TB  Lee YJ  Kim P  Kim CS  Oh DK 《Biotechnology letters》2004,26(8):623-627
Long-term cell recycle fermentations of Candida tropicalis were performed over 14 rounds of fermentation. The average xylitol concentrations, fermentation times, volumetric productivities and product yields for 14 rounds were 105 g l–1, 333 h, 4.4 g l–1 h–1 and 78%, respectively, in complex medium; and 110 g l–1, 284 h, 5.4 g l–1 h–1 and 81%, respectively, in a chemically defined medium. These productivities were 1.7 and 2.4 times those with batch fermentation in the complex and chemically defined media, respectively. The xylitol yield from xylose with cell recycle fermentation using the chemically defined medium was 81% (w/w), which was 7% greater than the xylitol yield with batch fermentation (74%); both modes of fermentation gave the same yield using the complex medium. These results suggest that the chemically defined medium is more suitable for production of xylitol than complex medium.  相似文献   

10.
The dimorphic fungus Mucor indicus was grown in different forms classified as purely filamentous, mostly filamentous, mostly yeast-like and purely yeast-like, and the relationship between morphology and metabolite production, inhibitor tolerance and the cell wall composition was investigated. Low concentrations of spores in the inoculum with subsequent aeration promoted filamentous growth, whereas higher spore concentrations and anaerobic conditions promoted yeast-like growth. Ethanol was the main metabolite with glycerol next under all conditions tested. The yields of ethanol from glucose were between 0.39 and 0.42 g g−1 with productivities of 3.2–5.0 g l−1 h−1. The ethanol productivity of mostly filamentous cells was increased from 3.9 to 5.0 g l−1 h−1 by the presence of oxygen, whereas aeration of purely yeast-like cells showed no such effect. All growth forms were able to tolerate 4.6 g l−1 furfural and 10 g l−1 acetic acid and assimilate the sugars, although with different consumption rates. The cell wall content of the fungus measured as alkali insoluble materials (AIM) of the purely yeast-like cells was 26% of the biomass, compared to 8% of the pure filaments. However, the chitosan concentration of the filaments was 29% of the AIM, compared to 6% of the yeast-like cells.  相似文献   

11.
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.  相似文献   

12.
Laccase-catalyzed oxidation of phenolic compounds in organic media   总被引:1,自引:0,他引:1  
Rhus vernificera laccase-catalyzed oxidation of phenolic compounds, i.e., (+)-catechin, (−)-epicatechin and catechol, was carried out in selected organic solvents to search for the favorable reaction medium. The investigation on reaction parameters showed that optimal laccase activity was obtained in hexane at 30 °C, pH 7.75 for the oxidation of (+)-catechin as well as for (−)-epicatechin, and in toluene at 35 °C, pH 7.25 for the oxidation of catechol. Ea and Q10 values of the biocatalysis in the reaction media of the larger log p solvents like isooctane and hexane were relatively higher than those in the reaction media of lower log p solvents like toluene and dichloromethane. Maximum laccase activity in the organic media was found with 6.5% of buffer as co-solvent. A wider range of 0–28 μg protein/ml in hexane than that of 0–16.7 μg protein/ml in aqueous medium was observed for the linear increasing conversion of (+)-catechin. The kinetic studies revealed that in the presence of isooctane, hexane, toluene and dichloromethane, the Km values were 0.77, 0.97, 0.53 and 2.9 mmol/L for the substrate of (+)-catechin; 0.43, 0.34, 0.14 and 3.4 mmol/L for (−)-epicatechin; 2.9, 1.8, 0.61 and 1.1 mmol/L for catechol, respectively, while the corresponding Vmax values were 2.1 × 10−2, 2.3 × 10−2, 0.65 × 10−2 and 0.71 × 10−2 δA/μg protein min); 1.8 × 10−2, 0.88 × 10−2, 0.19 × 10−2 and 1.0 × 10−2 δA/μg protein min); 0.48 × 10−2, 0.59 × 10−2, 0.67 × 10−2 and 0.54 × 10−2 δA/μg protein min), respectively. FT-IR indicated the formation of probable dimer from (+)-catechin in organic solvent. These results suggest that this laccase has higher catalytic oxidation capacity of phenolic compounds in suitable organic media and favorite oligomers could be obtained.  相似文献   

13.
Can soil Chytridiomycota survive and grow in different osmotic potentials?   总被引:1,自引:1,他引:0  
Twenty isolates from soil in the orders Spizellomycetales, Blastocladiales and Chytridiales (Chytridiomycota) grew on complex solid media supplemented with 10 g l−1 sodium chloride. In a synthetic liquid medium, 4.4 g l−1 sodium chloride strongly inhibited growth in three of the five isolates, possibly because of the effect of the ions or osmolarity of the solution. The maximum concentration for growth in synthetic liquid medium with different osmotic potentials using polyethylene glycol (PEG) varied considerably amongst the isolates. Three patterns of growth with increasing concentrations of PEG were evident among isolates within the genus Rhizophydium. Up to the concentration where growth ceased, the dry weight of each isolate either decreased, remained constant, or in one case, increased. Most of the fungi survived when incubated at room temperature for 7 d in complex liquid media supplemented with 35 g l−1 sodium chloride or 300 g l−1 PEG. These data indicate that soil Chytridiomycota can survive various osmotic potentials that may occur during the wetting and drying phases in soils.  相似文献   

14.
The yeast Cryptococcus flavus secretes a glycosylated α-amylase (Amy1) when grown in a starch-containing medium. The effects of N-glycosylation on secretion, enzyme activity, and stability of this glycoprotein were studied. Addition of tunicamycin (TM) to the medium at a concentration higher than 0.5 μg mL−1 affected C. flavus growth. Amy1 activity increased by 55% in the intracellular fraction after C. flavus growth in the presence of 0.5 μg mL−1 TM. SDS–PAGE and gel activity detection showed that native enzyme and deglycosylated enzyme had apparent molecular mass of 68 and 64.5 kDa, respectively. The N-glycosylation process did not affect either optimum pH or optimum temperature. The KM values of native and non-glycosylated α-amylases were 0.052 and 0.098 mg mL−1, and Vmax values were 0.038 and 0.047 mg min−1, respectively. However, the non-glycosylated form was more sensitive to inactivation by both the proteolytic enzyme trypsin and high temperature. Furthermore, the activity of the non-glycosylated enzyme was affected by Hg2+ and Cu2+ suggesting that N-glycosylation is involved in the folding of Amy1.  相似文献   

15.
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.  相似文献   

16.
A multi-functional enzyme ICChI with chitinase/lysozyme/exochitinase activity from the latex of Ipomoea carnea subsp. fistulosa was purified to homogeneity using ammonium sulphate precipitation, hydrophobic interaction and size exclusion chromatography. The enzyme is glycosylated (14–15%), has a molecular mass of 34.94 kDa (MALDI–TOF) and an isoelectric point of pH 5.3. The enzyme is stable in pH range 5.0–9.0, 80 °C and the optimal activity is observed at pH 6.0 and 60 °C. Using p-nitrophenyl-N-acetyl-β-d-glucosaminide, the kinetic parameters Km, Vmax, Kcat and specificity constant of the enzyme were calculated as 0.5 mM, 2.5 × 10−8 mol min−1 μg enzyme−1, 29.0 s−1 and 58.0 mM−1 s−1 respectively. The extinction coefficient was estimated as 20.56 M−1 cm−1. The protein contains eight tryptophan, 20 tyrosine and six cysteine residues forming three disulfide bridges. The polyclonal antibodies raised and immunodiffusion suggests that the antigenic determinants of ICChI are unique. The first fifteen N-terminal residues G–E–I–A–I–Y–W–G–Q–N–G–G–E–G–S exhibited considerable similarity to other known chitinases. Owing to these unique properties the reported enzyme would find applications in agricultural, pharmaceutical, biomedical and biotechnological fields.  相似文献   

17.
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.  相似文献   

18.
Forty species of fungi, representing a range of ecological and taxonomic groups, were tested for their ability to grow on agar media amended with lithium chloride (LiCl) at 1.5, 3 and 6 g l−1. Species of Trichoderma varied considerably in their sensitivity to LiCl; at one week on 6 g l−1 LiCl medium, the growth of seven species of Trichoderma was considerably inhibited; however, by three weeks at this level, four of the species tested were able to attain ≥30 % of control growth. Of the seven species tested, an isolate of T. viride was the most sensitive to LiCl in agar. Eleven other imperfect fungi also showed a range of ability to grow on agar amended with LiCl, from total inhibition to complete lack of inhibition. Six ascomycete fungi were greatly inhibited by LiCl at all levels; however, an isolate of Chaetomium globosum was highly tolerant of LiCl. Seven basidiomycete wood-decay fungi were quite sensitive to LiCl in agar, showing total to nearly total inhibition even at the lowest level; however, after three weeks, an isolate of Postia placenta was nearly uninhibited except at 6 g l−1. Five ectomycorrhizal basidiomycete fungi were totally inhibited by all levels of LiCl; however, one ectomycorrhizal imperfect fungus (Cenococcum graniforme) was able to grow at 3 g l−1 and was uninhibited at 1.5 g l−1. Four zygomycete fungus isolates were nearly unaffected in their growth by all levels of LiCl.  相似文献   

19.
The objective of this study was to determine how fungal morphology influences the volumetric cellulase productivity of Trichoderma reesei cultured in four media with lactose and lactobionic acid as fed-batch in a 7 L stirred tank bioreactor. The use of a cellulose–yeast extract culture medium yielded the highest enzyme production with a volumetric enzyme activity of 69.8 U L−1 h−1, and a maximum fungal biomass of 14.7 g L−1. These findings were associated with the following morphological characteristics of the fungus: total mycelia was 98% of total mean projected area, mean hyphae length of 10 mm, mean hyphae volume of 45.1 mm3, mean hyphae diameter of 7.9 μm, number of branches 9, and number of tips per hypha 29. A positive correlation was found between the total mycelia, the number of tips and the volumetric enzyme productivity, indicating the weight of these variables on the enzyme productivity.  相似文献   

20.
Biomass, primary production and nutrient budgets associated to Sarcocornia perennis subspecies (ssp.) alpini were studied in the Palmones River estuary salt marsh (Southern Spain) to evaluate the nutrient sequestration capacity of the low marsh. Above- and belowground living and dead biomass, as well as carbon, nitrogen and phosphorus content were monitored during 1 year. Additionally, the fate of aboveground detritus was evaluated in an experiment on litter decomposition. The detritus production of S. perennis ssp. alpini was almost equivalent to its annual primary production indicating a rapid turnover of biomass. We calculated that only 12% of the aboveground detritus was exported out of the low marsh while the rest was decomposed in the sediment with a rate of 0.8 year−1. Changes in concentrations of total carbon, nitrogen and phosphorus in the sediment showed patterns related to S. perennis ssp. alpini belowground biomass. Our results suggested that the sediment functions as a net sink for nutrients accumulating 550 g C m−2 year−1, 55 g N m−2 year−1, and 13 g P m−2 year−1.  相似文献   

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