Limit of change in unsaturation index of fatty acid composition of phospholipids at adaptation of molluscs to biogenic and abiogenic environmental factors

Comparative study of fatty acid composition of total phospholipids, as well as of phosphatidylcholine and phosphatidylethanolamine from hepatopancreas and leg muscle was carried out on several representatives of gastropod molluscs (Gastropoda) and on the bivalve mussel Mytilus edulus (Bivalvia). The objects of our study were marine littorins Littorina saxsatilis adapted to different temperature conditions of White Sea and Barents Sea, the freshwater lymnaea Lymnaea stagnalis infested by Trematoda, and mussels from the White and Black Seas. It was shown that depending on the existence conditions of the studied tissue or lipid, the maximal changes occurred in the percentage of saturated acids (4–83%); the percentage of unsaturated acids was less expressed (1–14%) and the changes in unsaturation index (UI), on average, did not exceed 20%. It was suggested that the revealed quantitative restriction of the UI change under the action of various external factors is a limit for maintenance of the membrane fluidity necessary for normal cell viability, specifically in the studied ectothermic molluscs.     

Effect of parasites on host adaptation to abiotic environmental factors: host-parasite relationship of trematode parthenites--mollusc system

This laboratory study examined the survival of extreme environmental conditions by the White Sea periwinkle Littorina saxatilis. Molluscs from localities with high and low prevalence of Microphallus piriformes, which is a representative of the "pygmaeus" group of digeneans (Microphallidae), were compared. These parasites have not a stage of free-living cercariae in their life cycle. Metacercariae mature inside the sporocysts parasitizing the molluscan host. No negative influence of infection was found on resistance of molluscs to prolonged desiccation and extremes of air and water temperature. On the contrary, significant lower mortality of high infected snails was observed in some experiments. Exposure to fresh water was the only treatment that caused more intensive mortality of high infected snails in comparison with low infected one. The results of the experiments were discussed taking into consideration the available data on mechanisms of molluscan resistance and features in the relationships of "pygmaeus" group sporocysts with the organism of molluscan host. It was emphasized that the wide spread opinion regarding the only negative influence of trematode infection on the resistance of infected molluscs should be revised.     

Changes produced by trematode larvae in the phospholipid fatty acid composition of digestive gland of the mollusc Littorina saxatilis

Lipids of the digestive gland of the mollusc Littorina saxatilis from the White and Barents Seas were studied. Changes of its biochemical composition are discussed in the connection with different temperature of the habitat and with infestation with trematode larvae. Comparative analysis of the fatty acid (FA) composition of each of phospholipids in intact molluscs has revealed essential differences. Phosphatidylcholine and monophosphatidylinositol (MPI) FA did not differ in the omega 3/omega 6 ratio, which is due to their tolerance to the temperature factor, whereas more unsaturated phospholipids--phosphatidylethanolamine (FEA), its plasmalogen form (pFEA), and phosphatidylserine--differed 1.5-2 times in the studied molluscs. Predominance of omega 3 acids in the Borents Sea molluscs undoubtedly is due to the lower habitat temperatures, as it provides a higher fluidity of membrane phospholipids. Infestation affected to the greatest degree the quantitative FA composition in pFEA and MPI. At infestation, out of all considered phospholipids, only in MPI there was revealed a threefold decrease of the content of eikosenoic acid C20 : 1, whereas in all other phospholipids, in the contrary, it increased. Monophosphatidylinositols also differed essentially from other phospholipids by the saturated FA amount, which changed the unsaturation index of these phospholipids. Since the functional significance of this minor phospholipid is determined by its participation in the so-called phosphatidylinositol system of the hormonal signal transduction, it seems interesting to elucidate whether an increase of this membrane phospholipid saturation at invasion affects the reflex connection between signals from receptors located in a parasite and enzymatic processes.     

Infection patterns in white sea blue mussels Mytilus edulis of different age and size with metacercariae of Himasthla elongata (Echinostomatidae) and Cercaria parvicaudata (Renicolidae)

Infection of mussels Mytilus edulis L. by 2 trematode species was studied in a natural intertidal population in the Chupa inlet of the White Sea. The prevalence of metacercariae of Himasthla elongata (Mehlis, 1831) and Cercaria parvicaudata (Stunkard & Shaw, 1931) in mussels reached 100% in 3 to 4 yr old molluscs and remained at this level in older individuals. Infection intensity increased evenly with the age of the molluscan host, showing a tendency to decrease only in the oldest (9 yr old) mussels. These patterns of age dynamics of prevalence and infection intensity were associated with accumulation of trematode larvae in the course of the molluscs' lives. Ability of metacercariae to exist in mussels for long periods (at least 2.5 yr) was verified in the course of an experiment, during which infected molluscs were kept in a subtidal net cage. Decrease of infection intensity in the oldest individuals may reflect selective mortality of the most severely infected molluscs. Among mussels of the same age, higher infection intensity values occurred in larger individuals. This may be due to an enhanced pumping rate in large molluscs, which increases the probability of cercariae, free-living trematode larvae, infecting them via water currents.     

Age–size structure of common bivalve mollusc populations in the White Sea: the causes of instability

Inter-annual fluctuations in the recruitment rate and size–age structure are typical for marine bivalve beds. Until now there is no common opinion about the causes of this variability. One of them may be related to the adult–larval interactions in mollusk populations. To test this suggestion and to reveal the possible causes of inter-annual instability in bed recruitment level we analyzed the long-term (9–30 years) dynamics of the size–age structure of 22 populations of 9 bivalve species in the White Sea. Inter-annual variability in the successful recruitment was typical of most studied bivalve beds. This phenomenon was apparently caused, on the one hand, by the intensity of molluscs’ intraspecific interactions, and on the other (no less), by the juvenile survival in their first winter. The bivalve stationary beds in the White Sea are likely the exception from the general rule. They can be formed in case of a relatively stable level of annual recruitment with a decrease in intensity of intraspecific competition. However, in this case, the stability of the bed size–age structure can be easily disrupted under unfavourable conditions for spat survival in their first winter.     

Effect of erythropoietin on the lipid composition of red blood cell membrane

Effect of Ep on [14C]acetate incorporation into different lipid fractions of RBC membranes in starved and phenylhydrazine-treated rats was studied. The incorporation was increased into both neutral and phospholipid fractions on Ep treatment to starved or phenylhydrazine-treated rats. A slight decrease in the ratio of neutral lipid to phospholipid was observed under the influence of Ep in starved rats (23%) or in phenylhydrazine-treated rats (36%). Incorporation of radioactivities into different phospholipid fractions of RBC membrane increased on Ep treatment to starved rats, whereas, the relative percentages of these phospholipids (except LPC) remained more or less unchanged under similar conditions. Phenylhydrazine treatment increased the relative percentage of PC and concomitantly decreased the percentage of Sph. Percentage composition of both these two phospholipids showed a tendency to return to their normal levels on administration of Ep to phenylhydrazine-treated rats. Ep decreased the sigma saturated/sigma unsaturated ratio of fatty acids in PE, PS, and PC of RBC membrane in starved rats. On the other hand, no significant change was observed in this ratio of fatty acids in the phospholipids except Sph of RBC membrane in the presence of phenylhydrazine and Ep. In Sph, the ratio went down under similar conditions.     

Benthic meiofaunal density and community composition in the deep White Sea and their temporal variations

In spite of the fact that shallow-water meiobenthos of the White Sea is a relatively well studied, the information on meiobenthic fauna from the deepest part of this sea is still very scanty. This study represents the first major study of the meiobenthos from the deep White Sea. The composition of the meiobenthic community, density and vertical distribution was studied during four sampling occasions in the deepest part of the Kandalaksha Depression (White Sea) in July 1998, October 1998, May 1999 and November 1999. Samples were collected from a depth of 270?m with the aid of a multicorer. The total density of meiobenthos in 1998 was twice than in 1999 (on average, 2,356 and 1,464 ind./10?cm², respectively). The most abundant meiobenthic group was Foraminifera (59?%), followed by Nematoda (26?%) and Harpacticoida (7?%). These relative and absolute abundance values are comparable with the same depth interval in Arctic and temperate regions. The density of foraminiferans and nematodes was higher in the autumn and lower in the summer. This may be explained by the mass propagation of these animals in the autumn season: the density of juvenile nematodes and small-sized foraminiferans increased significantly in the 1- to 4-cm-deep sediment layers in autumn. The size range of the meiobenthos in the deepest part of the White Sea was also comparable to deep-sea meiobenthos (the 63–125 and 125–250?μm size classes were most dominant).     

Composition and synthesis of fatty acids in atherosclerotic aortas of the pigeon

The composition, synthesis, and esterification of fatty acids were studied in aortas of White Carneau and Show Racer pigeons after perfusion of the aortas with a medium containing acetate-1-(14)C. For both breeds of pigeons the principal change in aortic fatty acids, in response to an atherogenic diet, was a marked increase in the percentage of oleic acid in the cholesteryl ester fraction. In atherosclerotic aortas incorporation of acetate-1-(14)C into the phospholipid and glyceride fractions increased 2-fold, while a much greater increase (up to 10-fold) was seen in incorporation into cholesteryl esters. In those birds receiving the atherogenic diet, palmitic acid accounted for approximately 50% of the fatty acid radioactivity, compared with approximately 25% from control aortas. Calculation of fatty acid synthesis showed the major newly synthesized fatty acids to be stearic acid in the phospholipid fraction; stearic, palmitic, and oleic acids in the glycerides; and oleic acid in the cholesteryl esters. The pattern of fatty acid synthesis was closely similar to the actual fatty acid composition of the aorta. In atherosclerotic aortas an increased synthesis of all fatty acids was seen, but the greatest increase was seen in the synthesis of oleic acid and its esterification to cholesterol.     

Effects of zinc on lipids of erythrocytes from carp (Cyprinus carpio L.) acclimated to different temperatures

We compared the effect of zinc (0.01, 0.1, 0.5 and 1 mM) at two temperatures (5 and 20 degrees C) on erythrocytes from summer and winter acclimatised carp. An increase in temperature from 5 to 20 degrees C increased the unsaturation index (UI) and relative proportion (UI/SFA) of unsaturated to saturated fatty acids in total lipids of the red cells. At 5 degrees C, the unsaturation index of phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) decreased (30-40%) in the presence of 1 mM zinc. The change in unsaturation of phospholipids in the presence of zinc at 5 degrees C is probably responsible for the alteration in structural integrity of erythrocyte membrane as observed by hemolysis and the decreased thiol group content in the erythrocytes. In light of this result, zinc may be considered an environmental hazard for these fish at low temperatures.     

Comparative morphofunctional analysis of the gastropod-trematode interactions

A morphofunctional aspect of pathogenesis in various mollusc--trematode combinations is very different. To evaluate the level of antagonism between the host and parasite, it is reasonable to use a summarized parameter of general physiological state of infected individuals. The somatic growth of the host could be used for that purpose. Analysis of original and reference data has shown, that the gastropod growth response to the trematode infection depends on the longevity of molluscs. The growth acceleration (gigantism) in infected individuals is common for snails with the intermediate longevity (3-4 yr), such as Hydrobia, Onobia and Bithynia (Prosobranchia: Rissoacea). As an exception, the gigantism is observed in the short-living species, which do not change the growth rate when they are parasitized: Biomphalaria, Bulinus, Helisoma and Lymnaea (Pulmonata: Basomathophora). Earlier, it was assumed that the single trend manifested in the infected long-living species (6-27 yr), such as Littorina (Prosobranchia: Littorinacea) and Cerithidea (Prosobranchia: Cerithiacea), in the decrease of the growth rate. The only case of the growth acceleration within the long-living molluscs was detected in the Littorina littorea from the White Sea infected with low pathogenic partenits of Cryptocotyle lingua (Heterophyidae). Based on the groups of snails with different longevity and being phylogenetically distant from each other, we can presume that the growth response to the infection correlates with the morphological peculiarities of hosts. The morphofunctional distinction in the system formed by trematodes and molluscs of different taxa are expressed in the parthenit localization in the host body and in the degree of digestive gland and/or gonad destriction. From the viewpoint of general physiological status of the host organism, the results of disfunctions in these organs are not similar. The destruction of digestive system ("energy power station" of organisms) is more fatal for infected individuals than a parasitic castration. Therefore, the localization of parasites in the mollusc gonad can be recognized as a parasitic adaptation to decrease the probability of a premature host's death and respectively to prevent the elimination of parasites. Phylogenetically distant gastropods with different life cycles use a diverse reproduction strategy, which implies a different proportion of gonad and digestive gland volume. Thus, snail species from different taxa are not similar in relation to the life space, which could be "granted" to the parasite without any risk to reduce a viability of the host. The space lack forces the parthenits parasitizing in the molluscs with the longer life span to occupy the digestive gland tissues, that increases their pathogenicity and decreases the host's growth rate.     

Potential impact of the main benthic amphipods on the eastern Weddell Sea shelf ecosystem (Antarctica)

As they represent one of the most diversified taxonomic groups on Antarctic bottoms, amphipods are likely to play a complex role in biogeochemical fluxes that occur within benthic ecosystems. The aim of this paper is to present, using both digestive tract analyses and relative species abundance data, the impact of amphipod feeding on different potential preys of the Weddell Sea. The study is based on data obtained for 29 representative amphipod species collected at 130 stations distributed along the eastern shelf of the Weddell Sea (depth range: 60-2,000 m) during three summer cruises, from 1989 to 1998. Sedimenting plankton particles (10-27%), crustaceans (22-32%) and fish carrion (5-18%) are the main food resources. Other abundant potential preys, such as molluscs or tunicates, do not seem to be consumed. Variations in the proportions of the different preyed food items are observed, mainly related to differences in relative amphipod species composition in samples. Presented results will help in refining ecological models of the prospected area, but also underline the need for accurate and reliable measurements of the feeding rates of Antarctic benthic organisms.     

Growth and longevity of Mytilus edulis (L.) from northeast Europe

The growth of mussels, Mytilus edulis (L.), was studied in most of the northeastern part of their distribution. The growth, longevity and maximal size of molluscs from 24 wild populations and one cultured population located in the White Sea and the southeast part of the Barents Sea were compared. The 25 studied populations were combined in six clusters. The maximal longevity and the size of the mussels varied between 7 and 18 years and 25.5 and 77.7 mm, respectively. The geographical location of the population within the studied region did not affect either maximal longevity or maximal size, or the growth rate of mussels. However, these parameters were influenced by local habitat conditions, primarily connected with the position within intertidal and subtidal zones. Animals inhabiting the intertidal zone were characterized by relatively low growth performance, a short life span and a small size. The longest life span was typical for deep subtidal mussels, whereas the highest growth rate was recorded in the cultured population and in the upper subtidal habitats. Growth patterns of Mytilus edulis in the subarctic White and the Arctic southeast Barents seas are similar to those reported from other parts of the area of distribution. Therefore, growth was mostly determined by local environmental factors, including those related to vertical zonation, rather than by latitude/longitude and related temperature effects.     

Changes in trace metal concentrations in the tissues of the White Sea mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> over the reproductive cycle

Seasonal changes in the concentrations and total amounts (contents) of Cd, Zn, and Cu in the mussel Mytilus edulis cultivated in the White Sea were studied over the reproductive cycle (prespawning, spawning, and postspawning stages). The results, when compared with published data on the closely related species M. trossulus from the Sea of Japan, suggest that the seasonal dynamics of trace element contents in mussel tissues are related to specific geochemical conditions, as well as to the dynamics of changes in soft tissue weight over the reproductive cycle. The contents of Cd and Cu in the mussels before, during, and after spawning changed similarly in the mollusks from the White Sea and the Sea of Japan. Changes in the Zn content at different stages of the reproductive cycle of the White Sea mussels were similar to those in mussels from the Sea of Japan but had smaller amplitude. The concentration of Zn in the White Sea mussels was before spawning the highest, but still lower than in mussels from the Sea of Japan. After the spawning, the Zn concentration in the White Sea mussels, in contrast to the Pacific mussels, decreased because of the redistribution of this element during the prespawning period from the somatic tissue into the gonad.     

Life history characteristics of the clam<Emphasis Type="Italic"> Mya arenaria</Emphasis> in the White Sea

Dynamics of Mya arenaria beds in two bights of the Chupa Inlet (Kandalaksha Bay, White Sea) were studied on a long-term basis. Observations were carried out at 1– to 3-year intervals from 1979 up to 1999. The studied soft-shell clam beds were characterised by a substantial instability of age structure. Since 1988, only one year-class has dominated in the beds while other generations have been scarce and recruitment was not observed. This pattern of Mya bed dynamics was related neither to interannual environmental changes nor to differential reproduction success or predation effects in the benthic assemblages. Favourable conditions for spat formation in 1988 (low abundance of other M. arenaria generations), as well as for juvenile survival during the following winter, resulted in high abundance of juveniles in both investigated locations in 1989. The mortality rate (μ) in this 1988 generation varied throughout the period of investigation and was related to age. The mortality level decreased for the first 2–4 years of the life cycle, then stabilised for the next 3–4 years, and eventually increased in subsequent years. Overall μ values ranged from 0 to 1.68 year^–1. The oldest specimens observed were 17 years old and had a maximum shell length of 79 mm. Significant differences in average growth rates were observed between molluscs of different locations. Communicated by H.-D. Franke     

Comparative Analysis of the Fatty Acid Profiles of Smolts of the Brown Trout <Emphasis Type="Italic">Salmo trutta</Emphasis> L. and Atlantic Salmon <Emphasis Type="Italic">Salmo salar</Emphasis> L. during Smoltification (Indera River,White Sea Basin)

The fatty acid status of the total lipids was studied in smolts of the brown trout and the Atlantic salmon collected in summer in the Indera River (White Sea basin). Higher 18:3ω-3/18:2ω-6, ω-3/ω-6, and 20:4ω-6/18:2ω-6 ratios were found in smolts of the Atlantic salmon in comparison to smolts of the brown trout. A higher amount of essential fatty acid 18:2ω-6 and an increased ratio of the sum of polyunsaturated fatty acids to the sum of saturated fatty acids in smolts of brown trout were observed. We have registered the differences in the ratios of the fatty acids, including physiologically active ones, which indicated species-specific physiological and biochemical processes during smoltification.     

Fauna associated with detached kelp in different types of subtidal habitats of the White Sea

The fauna, associated with Laminaria and other largebrown macroalgae was studied by using SCUBA anddredging in two different types of underwater habitatsof the White Sea.In shallow water fjords and bays, with a depth of nomore than 30–40 m, detached kelp (mainly Laminaria saccharina, L. digitata and Alaria esculenta) formed large accumulations. One ofthese benthic accumulations, which has existed morethan 20 years, was studied. It covers about2000 m², and is about 2 m thick. The upper layerof the accumulation of fronds is characterized by highturbulence and is well aerated. The lower layer ischaracterized by anoxic conditions. Mats of sulphurbacteria were not observed, although fronds in themiddle layer were covered by layers of cyanobacteria.About 50 species of macroinvertebrates were found,mainly species that are normally associated withliving kelp, such as the detritivorous species Ophiura robusta and Gammarus oceanicus, and fewspecies that are specific inhabitants of organic-richbiotopes in the White Sea such as Capitellacapitata, Ophryotrocha irinae and Nebaliabipes. It was remarkable that in the shallow waterbasins of the White Sea, the process of decompositionof brown algae in the sublittoral takes place withoutsea urchins, and no other macrofaunal form plays anecological role in the mechanical breakdown of theplant substratum, even not in the large accumulationsof detached kelp.Along the open rocky shoreline, communities associatedwith dead detached kelp were situated at a depth of60–90 m, 40–50 m below the belt of living kelp. Inthis deep zone, no macroinvertebrates typical of thekelp community in the photic zone were found. Duringthe passage from the shoreline to the deeper benthiccommunity, where sea urchins were dominant, all plantdebris became fragmented. These deeper benthiccommunities appeared to be the zone for decompositionof the detached kelp.     

Quantitative Phylogenomics of Within-Species Mitogenome Variation: Monte Carlo and Non-Parametric Analysis of Phylogeographic Structure among Discrete Transatlantic Breeding Areas of Harp Seals (Pagophilus groenlandicus)

Phylogenomic analysis of highly-resolved intraspecific phylogenies obtained from complete mitochondrial DNA genomes has had great success in clarifying relationships within and among human populations, but has found limited application in other wild species. Analytical challenges include assessment of random versus non-random phylogeographic distributions, and quantification of differences in tree topologies among populations. Harp Seals (Pagophilus groenlandicus Erxleben, 1777) have a biogeographic distribution based on four discrete trans-Atlantic breeding and whelping populations located on “fast ice” attached to land in the White Sea, Greenland Sea, the Labrador ice Front, and Southern Gulf of St Lawrence. This East to West distribution provides a set of a priori phylogeographic hypotheses. Outstanding biogeographic questions include the degree of genetic distinctiveness among these populations, in particular between the Greenland Sea and White Sea grounds. We obtained complete coding-region DNA sequences (15,825 bp) for 53 seals. Each seal has a unique mtDNA genome sequence, which differ by 6 ~ 107 substitutions. Six major clades / groups are detectable by parsimony, neighbor-joining, and Bayesian methods, all of which are found in breeding populations on either side of the Atlantic. The species coalescent is at 180 KYA; the most recent clade, which accounts for 66% of the diversity, reflects an expansion during the mid-Wisconsinan glaciation 40 ~ 60 KYA. F_ST is significant only between the White Sea and Greenland Sea or Ice Front populations. Hierarchal AMOVA of 2-, 3-, or 4-island models identifies small but significant Φ_SC among populations within groups, but not among groups. A novel Monte-Carlo simulation indicates that the observed distribution of individuals within breeding populations over the phylogenetic tree requires significantly fewer dispersal events than random expectation, consistent with island or a priori East to West 2- or 3-stepping-stone biogeographic models, but not a simple 1-step trans-Atlantic model. Plots of the cumulative pairwise sequence difference curves among seals in each of the four populations provide continuous proxies for phylogenetic diversification within each. Non-parametric Kolmogorov-Smirnov (K-S) tests of maximum pairwise differences between these curves indicates that the Greenland Sea population has a markedly younger phylogenetic structure than either the White Sea population or the two Northwest Atlantic populations, which are of intermediate age and homogeneous structure. The Monte Carlo and K-S assessments provide sensitive quantitative tests of within-species mitogenomic phylogeography. This is the first study to indicate that the White Sea and Greenland Sea populations have different population genetic histories. The analysis supports the hypothesis that Harp Seals comprises three genetically distinguishable breeding populations, in the White Sea, Greenland Sea, and Northwest Atlantic. Implications for an ice-dependent species during ongoing climate change are discussed.     

Extender Supplementation with Antioxidants Selected after the Evaluation of Sperm Susceptibility to Oxidative Challenges in Goats

This study aimed to detect the most deleterious ROS for goat sperm and then supplemented the extender with a proper antioxidant. For this, 12 adult goats (aged 1–7) were used. Fresh samples were submitted to challenge with different ROS (superoxide anion, hydrogen peroxide, and hydroxyl radical) and malondialdehyde (MDA—toxic product of lipid peroxidation). After experiment 1, sperms were cryopreserved in extenders supplemented to glutathione peroxidase (Control: 0?UI/mL; GPx1: 1?UI/mL; GPx5: 5?UI/mL, and GPx10: 10?UI/mL) and catalase (Control: 0?UI/mL; CAT60: 60?UI/mL; CAT120: 120?UI/mL, and CAT240: 240?UI/mL). Each sample was evaluated by motility, plasma membrane integrity (eosin/nigrosin), acrosome integrity (fast green/rose bengal), sperm morphology, assay of the sperm chromatin structure, mitochondrial activity (3,3-diaminobenzidine), and measurement of lipid peroxidation (thiobarbituric acid reactive substances [TBARS]). It was possible to observe a mitochondrial dysfunction (DAB—Class IV) and low membrane integrity after hydrogen peroxide action. However, the high rates of TBARS were observed on hydroxyl radical. CAT240 presents the lower percentage of plasma membrane integrity. It was possible to attest that hydrogen peroxide and hydroxyl radical are the more harmful for goat sperm. Antioxidant therapy must be improving perhaps using combination between antioxidants.     

Distribution of the Harp Seal Whelping Grounds in the White Sea 1960s–1990s

Analysis of air survey data has shown that from the 1960s to the 1990s the whelping grounds of the harp seal Phoca groenlandica formed at the end of February through the first days of March in two regions of the White Sea: in the eastern part of Bassein and in Gorlo. The areas of the whelping grounds varied depending on the current ice conditions. It was recorded that, despite ice conditions unfavorable for the pups' survival that developed in some years, in general the ice regime of the White Sea was favorable for reproduction of the White Sea population of the harp seal.     

Combination use of ultrasound irradiation and ionic liquid in enzymatic isomerization of glucose to fructose

The synthetic effect of the combination use of ultrasound irradiation (UI) and ionic liquid (IL) on improving enzyme activity was studied when they were employed in isomerization of glucose to fructose by immobilized glucose isomerase (IGI, produced from streptomyces murinus and immobilized on silica). Both of UI and IL [EMIM][Cl], which was screened as the best medium for this reaction, were found to increase the enzyme activity in isomerization reaction. And a further increase of enzyme activity was observed by combination use of UI and IL. A systematic screening and optimization of the reaction parameters in ILs under UI on the IGI activity were performed. Under the optimum reaction conditions, 45.3% yield of fructose was achieved in 10 h under UI in [EMIM][Cl], compared to only 41.5% yield under stirring in [EMIM][Cl], 44.2% under UI without [EMIM][Cl] and 38.9% under stirring without [EMIM][Cl] in 12 h, respectively. High thermal stability and reusability of IGI was also observed under UI in [EMIM][Cl]. These results indicated that the combination use of UI and IL might be a fast and efficient method for enzymatic isomerization of glucose to fructose.