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Christopher P Saint - One of the best experts on this subject based on the ideXlab platform.
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EXPRESSION OF THE Geosmin SYNTHASE GENE IN THE CYANOBACTERIUM ANABAENA CIRCINALIS AWQC318(1).
Journal of phycology, 2011Co-Authors: Steven Giglio, Christopher P Saint, Paul MonisAbstract:The occurrence of taste and odor episodes attributed to Geosmin continues to trouble water utilities worldwide, and only recently have advances been made in our fundamental understanding of the biochemical and genetic mechanisms responsible for the production of Geosmin in microorganisms. For the first time, we have examined the expression of the Geosmin synthase gene and corresponding Geosmin production by Anabaena circinalis Rabenh. ex Bornet et Flahault AWQC318 under conditions of continuous light illumination and the removal of light as a stimulus and demonstrate that the expression of Geosmin synthase appears to be constitutive under these conditions. The decrease in Geosmin synthase transcription post maximum cell numbers and stationary phase suggests that a decrease in isoprenoid synthesis may occur before a decrease in the transcription of ribosomal units as the process of cell death is initiated.
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biodegradation of Geosmin by a novel gram negative bacterium isolation phylogenetic characterisation and degradation rate determination
Water Research, 2009Co-Authors: Daniel Hoefel, Christopher P Saint, Paul Monis, Gayle NewcombeAbstract:Biologically active sand filters within water treatment plants (WTPs) are now recognised as an effective barrier for the removal of Geosmin. However, little is known regarding the actual microbiological processes occurring or the bacteria capable of degrading Geosmin. This study reports the enrichment and isolation of a Gram-negative bacterium, Geo48, from the biofilm of a WTP sand filter where the isolate was shown to effectively degrade Geosmin individually. Experiments revealed that Geo48 degraded Geosmin in a planktonic state by a pseudo-first-order mechanism. Initial Geosmin concentrations ranging from 100 to 1000ng/l were shown to directly influence Geosmin degradation in reservoir water by Geo48, with rate constants increasing from 0.010h(-1) (R(2)=0.93) to 0.029h(-1) (R(2)=0.97) respectively. Water temperature also influenced degradation of Geosmin by Geo48 where temperatures of 11, 22 and 30 degrees C resulted in rate constants of 0.017h(-1) (R(2)=0.98), 0.023h(-1) (R(2)=0.91) and 0.019h(-1) (R(2)=0.85) respectively. Phylogenetic analysis using the 16S rRNA gene of Geo48 revealed it was a member of the Alphaproteobacteria and clustered with 99% bootstrap support with an isolate designated Geo24, a Sphingopyxis sp. previously described as degrading Geosmin but only as a member of a bacterial consortium. Of the previously described bacteria, Geo48 was most similar to Sphingopyxis alaskensis (97.2% sequence similarity to a 1454bp fragment of the 16S rRNA gene). To date, this is the only study to report the isolation and characterisation of a Gram-negative bacterium from a biologically active sand filter capable of the sole degradation of Geosmin.
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enhancing the biofiltration of Geosmin by seeding sand filter columns with a consortium of Geosmin degrading bacteria
Water Research, 2009Co-Authors: Bridget Mcdowall, Lionel Ho, Daniel Hoefel, Christopher P Saint, Gayle NewcombeAbstract:Geosmin is a secondary metabolite that can be produced by many species of cyanobacteria and Actinomycetes. It imparts a musty/earthy taste and odour to drinking water which can result in consumer complaints and a general perception that there is a problem with the water quality. As Geosmin is recalcitrant to conventional water treatment, processes are sought to ensure effective removal of this compound from potable water. Biological filtration (biofiltration) is an attractive option for Geosmin removal as this compound has been shown to be biodegradable. However, effective biofiltration of Geosmin can be site specific as it is highly dependent upon the types of organism present and there is often an extended acclimation period before efficient removals are achieved. We report here, a novel approach to enhance the biofiltration of Geosmin by seeding sand filter columns with a bacterial consortium previously shown to be capable of effectively degrading Geosmin. Geosmin removals of up to 75% were evident through sand columns which had been inoculated with the Geosmin-degrading bacteria, when compared with non-inoculated sand columns where Geosmin removals were as low as 25%. These low Geosmin removals through the non-inoculated sand columns are consistent with previous studies and were attributed to physical/abiotic losses. The presence of an existing biofilm was shown to influence Geosmin removal, as the biofilm allowed for greater attachment of the Geosmin-degrading consortium (as determined by an ATP assay), and enhanced removals of Geosmin. Minimal difference in Geosmin removal was observed when the Geosmin-degrading bacteria were inoculated into the sand columns containing either an active or inactive biofilm.
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cooperative biodegradation of Geosmin by a consortium comprising three gram negative bacteria isolated from the biofilm of a sand filter column
Letters in Applied Microbiology, 2006Co-Authors: Daniel Hoefel, Lionel Ho, Alexandra Keegan, W Aunkofer, Paul Monis, Gayle Newcombe, Christopher P SaintAbstract:Aims: To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, Geosmin. In doing so, to investigate if these organisms degrade Geosmin either individually or if an alternative mechanism is utilized. Methods and Results: Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with Geosmin as the sole carbon source. By day 51, 21·7 mg l−1 of Geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2·12 log10 increase in active bacterial numbers as measured using the BacLightTM bacterial viability kit and flow cytometric enumeration. During the onset of Geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of Geosmin, when present as either the sole carbon source (ranging from 40 ng l−1 to 20 mg l−1) or when spiked into sterile reservoir water (37 and 131 ng l−1), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading Geosmin either individually or in any combination of two. Conclusions: This study has reported, for the first time, the cooperative degradation of Geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column. Significance and Impact of the Study: These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of Geosmin by bacteria, as such studies may be complicated by the discovery of Geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.
Daniel Hoefel - One of the best experts on this subject based on the ideXlab platform.
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biodegradation of Geosmin by a novel gram negative bacterium isolation phylogenetic characterisation and degradation rate determination
Water Research, 2009Co-Authors: Daniel Hoefel, Christopher P Saint, Paul Monis, Gayle NewcombeAbstract:Biologically active sand filters within water treatment plants (WTPs) are now recognised as an effective barrier for the removal of Geosmin. However, little is known regarding the actual microbiological processes occurring or the bacteria capable of degrading Geosmin. This study reports the enrichment and isolation of a Gram-negative bacterium, Geo48, from the biofilm of a WTP sand filter where the isolate was shown to effectively degrade Geosmin individually. Experiments revealed that Geo48 degraded Geosmin in a planktonic state by a pseudo-first-order mechanism. Initial Geosmin concentrations ranging from 100 to 1000ng/l were shown to directly influence Geosmin degradation in reservoir water by Geo48, with rate constants increasing from 0.010h(-1) (R(2)=0.93) to 0.029h(-1) (R(2)=0.97) respectively. Water temperature also influenced degradation of Geosmin by Geo48 where temperatures of 11, 22 and 30 degrees C resulted in rate constants of 0.017h(-1) (R(2)=0.98), 0.023h(-1) (R(2)=0.91) and 0.019h(-1) (R(2)=0.85) respectively. Phylogenetic analysis using the 16S rRNA gene of Geo48 revealed it was a member of the Alphaproteobacteria and clustered with 99% bootstrap support with an isolate designated Geo24, a Sphingopyxis sp. previously described as degrading Geosmin but only as a member of a bacterial consortium. Of the previously described bacteria, Geo48 was most similar to Sphingopyxis alaskensis (97.2% sequence similarity to a 1454bp fragment of the 16S rRNA gene). To date, this is the only study to report the isolation and characterisation of a Gram-negative bacterium from a biologically active sand filter capable of the sole degradation of Geosmin.
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enhancing the biofiltration of Geosmin by seeding sand filter columns with a consortium of Geosmin degrading bacteria
Water Research, 2009Co-Authors: Bridget Mcdowall, Lionel Ho, Daniel Hoefel, Christopher P Saint, Gayle NewcombeAbstract:Geosmin is a secondary metabolite that can be produced by many species of cyanobacteria and Actinomycetes. It imparts a musty/earthy taste and odour to drinking water which can result in consumer complaints and a general perception that there is a problem with the water quality. As Geosmin is recalcitrant to conventional water treatment, processes are sought to ensure effective removal of this compound from potable water. Biological filtration (biofiltration) is an attractive option for Geosmin removal as this compound has been shown to be biodegradable. However, effective biofiltration of Geosmin can be site specific as it is highly dependent upon the types of organism present and there is often an extended acclimation period before efficient removals are achieved. We report here, a novel approach to enhance the biofiltration of Geosmin by seeding sand filter columns with a bacterial consortium previously shown to be capable of effectively degrading Geosmin. Geosmin removals of up to 75% were evident through sand columns which had been inoculated with the Geosmin-degrading bacteria, when compared with non-inoculated sand columns where Geosmin removals were as low as 25%. These low Geosmin removals through the non-inoculated sand columns are consistent with previous studies and were attributed to physical/abiotic losses. The presence of an existing biofilm was shown to influence Geosmin removal, as the biofilm allowed for greater attachment of the Geosmin-degrading consortium (as determined by an ATP assay), and enhanced removals of Geosmin. Minimal difference in Geosmin removal was observed when the Geosmin-degrading bacteria were inoculated into the sand columns containing either an active or inactive biofilm.
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cooperative biodegradation of Geosmin by a consortium comprising three gram negative bacteria isolated from the biofilm of a sand filter column
Letters in Applied Microbiology, 2006Co-Authors: Daniel Hoefel, Lionel Ho, Alexandra Keegan, W Aunkofer, Paul Monis, Gayle Newcombe, Christopher P SaintAbstract:Aims: To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, Geosmin. In doing so, to investigate if these organisms degrade Geosmin either individually or if an alternative mechanism is utilized. Methods and Results: Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with Geosmin as the sole carbon source. By day 51, 21·7 mg l−1 of Geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2·12 log10 increase in active bacterial numbers as measured using the BacLightTM bacterial viability kit and flow cytometric enumeration. During the onset of Geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of Geosmin, when present as either the sole carbon source (ranging from 40 ng l−1 to 20 mg l−1) or when spiked into sterile reservoir water (37 and 131 ng l−1), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading Geosmin either individually or in any combination of two. Conclusions: This study has reported, for the first time, the cooperative degradation of Geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column. Significance and Impact of the Study: These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of Geosmin by bacteria, as such studies may be complicated by the discovery of Geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.
Lionel Ho - One of the best experts on this subject based on the ideXlab platform.
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enhancing the biofiltration of Geosmin by seeding sand filter columns with a consortium of Geosmin degrading bacteria
Water Research, 2009Co-Authors: Bridget Mcdowall, Lionel Ho, Daniel Hoefel, Christopher P Saint, Gayle NewcombeAbstract:Geosmin is a secondary metabolite that can be produced by many species of cyanobacteria and Actinomycetes. It imparts a musty/earthy taste and odour to drinking water which can result in consumer complaints and a general perception that there is a problem with the water quality. As Geosmin is recalcitrant to conventional water treatment, processes are sought to ensure effective removal of this compound from potable water. Biological filtration (biofiltration) is an attractive option for Geosmin removal as this compound has been shown to be biodegradable. However, effective biofiltration of Geosmin can be site specific as it is highly dependent upon the types of organism present and there is often an extended acclimation period before efficient removals are achieved. We report here, a novel approach to enhance the biofiltration of Geosmin by seeding sand filter columns with a bacterial consortium previously shown to be capable of effectively degrading Geosmin. Geosmin removals of up to 75% were evident through sand columns which had been inoculated with the Geosmin-degrading bacteria, when compared with non-inoculated sand columns where Geosmin removals were as low as 25%. These low Geosmin removals through the non-inoculated sand columns are consistent with previous studies and were attributed to physical/abiotic losses. The presence of an existing biofilm was shown to influence Geosmin removal, as the biofilm allowed for greater attachment of the Geosmin-degrading consortium (as determined by an ATP assay), and enhanced removals of Geosmin. Minimal difference in Geosmin removal was observed when the Geosmin-degrading bacteria were inoculated into the sand columns containing either an active or inactive biofilm.
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cooperative biodegradation of Geosmin by a consortium comprising three gram negative bacteria isolated from the biofilm of a sand filter column
Letters in Applied Microbiology, 2006Co-Authors: Daniel Hoefel, Lionel Ho, Alexandra Keegan, W Aunkofer, Paul Monis, Gayle Newcombe, Christopher P SaintAbstract:Aims: To isolate and identify bacteria from a sand filter column capable of degrading the taste and odour compound, Geosmin. In doing so, to investigate if these organisms degrade Geosmin either individually or if an alternative mechanism is utilized. Methods and Results: Geosmin-degrading bacteria from a biologically active sand filter column were enriched by their growth in a minimal medium supplemented with Geosmin as the sole carbon source. By day 51, 21·7 mg l−1 of Geosmin had been degraded as determined by solid-phase microextraction gas chromatography/mass spectrometry, and was accompanied by a 2·12 log10 increase in active bacterial numbers as measured using the BacLightTM bacterial viability kit and flow cytometric enumeration. During the onset of Geosmin degradation, the predominance of three bacteria, most similar to previously cultured species of Sphingopyxis alaskensis, Novosphingobium stygiae and Pseudomonas veronii based on 16S rRNA gene sequences was detected by denaturing gradient gel electrophoresis. Subsequent isolation of these organisms revealed that degradation of Geosmin, when present as either the sole carbon source (ranging from 40 ng l−1 to 20 mg l−1) or when spiked into sterile reservoir water (37 and 131 ng l−1), occurred only when all three isolates were present. None of the isolates was shown to be capable of degrading Geosmin either individually or in any combination of two. Conclusions: This study has reported, for the first time, the cooperative degradation of Geosmin by a consortium comprising three gram-negative bacteria isolated from a biologically active sand filter column. Significance and Impact of the Study: These results are important for researchers currently employing molecular-based approaches to further understand the biodegradation of Geosmin by bacteria, as such studies may be complicated by the discovery of Geosmin degradation occurring by a consortium. This study also advances the knowledge surrounding the types of bacteria capable of degrading the taste and odour compound, as investigations to date regarding this are limited.
David E Cane - One of the best experts on this subject based on the ideXlab platform.
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Geosmin biosynthesis. Mechanism of the fragmentation-rearrangement in the conversion of germacradienol to Geosmin.
Journal of the American Chemical Society, 2007Co-Authors: Jiaoyang Jiang, David E CaneAbstract:Geosmin (1) is responsible for the characteristic odor of moist soil. Incubation of farnesyl diphosphate (2, FPP) with recombinant Streptomyces coelicolor germacradienol/Geosmin synthase generated Geosmin (1), germacradienol (3), germacrene D (4), octalin 5, and acetone, which was trapped as 2,2-dimethylthiazolidine (9) by reaction with cysteamine. The acetone was shown to be derived by fragmentation of the 2-hydroxypropyl moiety of germacradienol by incubation with [13,13,13-2H3]FPP (2a), giving rising to the corresponding derivative of d3-acetone, 9a. GC−MS analysis of the labeling pattern of [6-2H]Geosmin (1b) resulting from the incubation of germacradienol/Geosmin synthase with [2-2H]FPP (2b) revealed that the H-2 proton on FPP undergoes the predicted 1,2-hydride shift to ring B of Geosmin. Both sets of experimental results are consistent with a proposed mechanism of Geosmin formation involving protonation-cyclization of germacradienol with loss of the 2-hydroxypropyl moiety as acetone by a retro-Prin...
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Geosmin Biosynthesis in Streptomyces avermitilis . Molecular Cloning, Expression, and Mechanistic Study of the Germacradienol/Geosmin Synthase
The Journal of Antibiotics, 2006Co-Authors: David E Cane, Seiji Kobayashi, Xiaofei He, Satoshi Omura, Haruo IkedaAbstract:Geosmin Biosynthesis in Streptomyces avermitilis . Molecular Cloning, Expression, and Mechanistic Study of the Germacradienol/Geosmin Synthase
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Geosmin biosynthesis in streptomyces avermitilis molecular cloning expression and mechanistic study of the germacradienol Geosmin synthase
The Journal of Antibiotics, 2006Co-Authors: David E Cane, Seiji Kobayashi, Satoshi ōmura, Haruo IkedaAbstract:Geosmin Biosynthesis in Streptomyces avermitilis . Molecular Cloning, Expression, and Mechanistic Study of the Germacradienol/Geosmin Synthase
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Geosmin Biosynthesis in Streptomyces avermitilis. Molecular Cloning, Expression, and Mechanistic Study of the Germacradienol/Geosmin Synthase
The Journal of Antibiotics, 2006Co-Authors: David E Cane, Seiji Kobayashi, Satoshi Ōmura, Haruo IkedaAbstract:Geosmin ( 1 ) is responsible for the characteristic odor of moist soil. The Gram-positive soil bacterium Streptomyces avermitilis produces Geosmin ( 1 ) as well as its precursor germacradienol ( 3 ). The S. avermitilis gene SAV2163 ( geoA ) is extremely similar to the S. coelicolor A3(2) SCO6073 gene that encodes a germacradienol/Geosmin synthase. S. avermitilis mutants with a deleted geoA were unable to produce either germacradienol ( 3 ) or Geosmin ( 1 ). Biosynthesis of both compounds was restored by introducing an intact geoA gene into the mutants. Incubation of recombinant GeoA, encoded by the SAV2163 gene of S. avermitilis , with farnesyl diphosphate ( 2 ) in the presence of Mg^2+ gave a mixture of (4 S ,7 R )-germacra-1(10) E ,5 E -diene-11-ol ( 3 ) (66%), (7 S )-germacrene D ( 4 ) (24%), Geosmin ( 1 ) (8%), and a hydrocarbon, tentatively assigned the structure of octalin 5 (2%). Incubation of this germacradienol/Geosmin synthase with [1,1-^2H_2]FPP ( 2a ) gave Geosmin-d_1 ( 1a ), as predicted. When recombinant GeoA from either S. avermitilis or S. coelicolor A3(2) was incubated with nerolidyl diphosphate ( 8 ), only the acyclic elimination products β-farnesene ( 10 ), ( Z )-α-farnesene ( 11 ), and ( E )-α-farnesene ( 12 ) were formed, thereby ruling out nerolidyl diphosphate as an intermediate in the conversion of farnesyl diphosphate to Geosmin, germacradienol, and germacrene D.
Johan W. Schrama - One of the best experts on this subject based on the ideXlab platform.
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Effect of feeding during off-flavour depuration on Geosmin excretion by Nile tilapia (Oreochromis niloticus)
Aquaculture, 2021Co-Authors: Edward Schram, Johan A.j. Verreth, Albertinka J. Murk, Christiaan Kwadijk, Angelo Hofman, Ainhoa Blanco, Johan W. SchramaAbstract:Abstract The effect of feeding during off-flavour depuration on the elimination of Geosmin from muscle tissue (fillet) and ovaries as a model for caviar was assessed in Nile tilapia (Oreochromis niloticus) (mean ± SD weight of 185 ± 15.0 g). The experiment had a 2 × 4 factorial design with feeding level (starved or fed) and depuration time (24, 48, 72 and 96 h) as factors with duplicates for each of the 8 treatment combinations. Fish were normally loaded with Geosmin prior to the experiment. During off-flavour depuration Geosmin levels in fillet and ovary declined over time in both fed and starved tilapia. In fed tilapia Geosmin declined faster from the ovaries compared to starved fish (p = 0.018). The same trend of a faster decline was observed for the muscle tissue (fillets) of fed tilapia, though only numerically (p = 0.11). Because faster Geosmin elimination paralleled with high blood lipids, we do not rule out that blood lipids are involved in Geosmin transport via the circulatory system and that low blood lipid levels are limiting Geosmin elimination in starved fish. No difference in Geosmin elimination rate was detected between ovary and muscle tissue in Nile tilapia. Off-flavour depuration time is strongly reduced when farmers adopt a practice of feeding Nile tilapia during off-flavour depuration.
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Experimental validation of Geosmin uptake in rainbow trout, Oncorhynchus mykiss (Waldbaum) suggests biotransformation
Aquaculture Research, 2017Co-Authors: Edward Schram, Tobias Van Kooten, Jan W Van De Heul, Johan W. Schrama, Johan A.j. Verreth, Christiaan Kwadijk, Harm Kampen, Albertinka J. MurkAbstract:The bioconcentration of waterborne Geosmin in rainbow trout, Oncorhynchus mykiss (Waldbaum) was assessed. Fifty rainbow trout with a mean (SD) weight of 226.6 (29.0) g and lipid content of 6.2 (0.6) % (w/w) were exposed to Geosmin in static water for 0, 2, 4, 6, 8, 12, 24, 36, 48 and 120 hr, with one tank containing five fish for eac h exposure period. Geosmin concentrations were measured in fish tissue and water samples collected over time. With time the Geosmin concentration in the fish increased and decreased in the water. However, the total absolute amount of Geosmin in the system declined over time which could be explained by induction of biotransformation. This is in accordance with the decreasing lipid normalized Geosmin levels in the liver compared with the liver-free carcass. Geosmin distribution within rainbow trout clearly is not exclusively governed by the lipid content of tissues. In vivo Geosmin bioconcentration in rainbow trout is slower and the body burden reached is lower than the generally accepted theoretical model predicts.
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Geosmin depuration from European eel (Anguilla anguilla) is not affected by the water renewal rate of depuration tanks
Aquaculture Research, 2017Co-Authors: Edward Schram, Tobias Van Kooten, Jan W Van De Heul, Johan W. Schrama, Johan A.j. Verreth, Albertinka J. MurkAbstract:This study established that Geosmin depuration from European eel is not affected by the water renewal rate of depuration tanks. A general fish bioaccumulation model extended with terms that account for effects of tank water renewal rate and system losses of chemicals, predicted strong effects of the water renewal rate of depuration tanks on Geosmin depuration from European eel. Model predictions were validated in a depuration experiment with Geosmin-loaded European eel (n = 95) with a mean (SD) individual weight of 134.4 (5.0) g and a mean (SD) lipid content of 33.7 (2.8) % (w/w). Fish were depurated for 24, 48 or 72 h at three different tank water renewal rates (0.3, 3.3 and 33 day−1). Treatments were installed by three different mean (SD) water flow rates (13.8 (1.3), 143.5 (9.2) and 1511 (80) L kg fish−1 day−1) over 30-L tanks. Eels eliminated Geosmin from their bodies, but unlike the model predicted, this was independent of the water renewal rate of the depuration tanks. Although being eliminated from the fish, Geosmin hardly appeared and certainly did not accumulate in the water of the depuration tanks as the model predicted. This observation may be explained by Geosmin being eliminated from eel as metabolite rather than the parent compound. Geosmin elimination from eel seems not to occur according to the generally accepted passive diffusion mechanism for excretion of lipophilic chemicals, and Geosmin biotransformation by the eel seems indicated. Clearly Geosmin depuration from European eel cannot be enhanced by increasing water renewal rates of depuration tanks.
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Effects of exercise and temperature on Geosmin excretion by European eel (Anguilla anguilla)
Aquaculture, 2016Co-Authors: Edward Schram, Johan W. Schrama, Christiaan Kwadijk, Kasper Kusters, Arjan P. PalstraAbstract:Abstract The presence of Geosmin in fish products causes an earthy or musty off-flavour. To avoid economic damage resulting from market entrance of off-flavoured fish products, fish farmers utilize the reversibility of Geosmin uptake to depurate the off-flavours from their fish crops by holding them in clean water just before harvest. To improve this process, effects of exercise and temperature on the excretion of Geosmin by European eel ( Anguilla anguilla ) were assessed. Fish loaded with Geosmin were depurated for 23 h during which they were subjected to combinations of exercise (spontaneous swimming activity at 0.05 m s − 1 or forced swimming at optimal swimming speed of 0.55 m s − 1 ) and temperature (15 °C or 25 °C) treatments. Oxygen consumption was measured during depuration. Whole body Geosmin concentrations were measured in samples collected at t = 0 and t = 23 h to assess Geosmin excretion. Geosmin excretion by European eel was clearly enhanced by exercise, but temperature had no statistically significant effect. Exercise increased oxygen consumption, which in turn showed a positive linear relation with Geosmin excretion. These findings support the idea that the physiological responses aimed at increasing oxygen uptake also affect the branchial exchange of lipophilic xenobiotic chemicals between the fish and its surroundings. Exercise can be used to reduce the time required to depurate off-flavours from fish. These findings are relevant for aquaculture industries confronted with off-flavoured fish crops. Statement of relevance Fish raised in land-based aquaculture systems may bio-concentrate Geosmin, a lipophilic organic compound produced by microbiota. The presence of Geosmin in fish products causes an earthy or musty off-flavour which human consumers do not appreciate and this poses one of the most significant economic problems for land-based aquaculture. To avoid economic damage resulting from market entrance of off-flavoured fish, fish farmers utilize the reversibility of Geosmin bio-concentration to depurate the off-flavours from their fish crops. To this end fish are kept in water free of Geosmin just before harvest. This procedure, however, is not always sufficiently effective and it is costly as it requires time, effort and use of specific facilities. Therefore better understanding of factors enhancing the Geosmin excretion is needed to be able to improve the off-flavour depuration process. This study established that forced exercise during off-flavour depuration increases the rate at which European eel eliminates Geosmin from its body. Forcing fish to swim during off-flavour depuration shortens the required depuration time. This finding is relevant for the aquaculture industries confronted with off-flavoured fish crops.
