Viridepyronone, a new antifungal 6-substituted 2H-pyran-2-one produced by Trichoderma viride

A new antifungal 6-substituted 2H-pyran-2-one, named viridepyronone, has been isolated from a cultural filtrate of a strain of Trichoderma viride showing antagonistic activity in vitro toward Sclerotium rolfsii, which is the causal agent of crown and stem rot of artichoke. Viridepyronone was characterized as 6-(4-oxopentyl)-2H-pyran-2-one 2 with spectroscopic methods. Bioassays showed that viridepyronone had a good antifungal activity against S. rolfsii, and its minimum inhibitory concentration (over 90% inhibition) was found to be 196 microg/mL. This is the first report of viridepyronone produced by any species of fungi.     

Antifungal activity of 4-methyl-6-alkyl-2H-pyran-2-ones

A number of 4-methyl-6-alkyl-alpha-pyrones were synthesized and characterized on the basis of 1H NMR and mass spectroscopy. These compounds were tested in vitro against pathogenic fungi, namely, Sclerotium rolfsii Saccardo, Rhizoctonia bataticola (Taub.) Butler, Pythium aphanidermatum (Edson) Fitz., Macrophomina phaseolina (Tassi), Pythium debaryanum (Hesse), and Rhizoctonia solani Nees. Lower homologues were less effective, whereas compounds such as 4-methyl-6-butyl-alpha-pyrone, 4-methyl-6-pentyl-alpha-pyrone, 4-methyl-6-hexyl-alpha-pyrone, and 4-methyl-6-heptyl-alpha-pyrone were found effective against all of the test fungi. They inhibited mycelial growth by approximately 50% (ED50) at 15-50 microg/mL. 4-Methyl-6-hexyl-alpha-pyrone, which was found most effective, was tested against S. rolfsii in a greenhouse at 1, 5, and 10% concentrations. The 10% aqueous emulsion of 4-methyl-6-hexyl-alpha-pyrone suppressed disease development in tomato by 90-93% as compared with the untreated infested soil in the greenhouse after 35 days of treatment.     

Microbial and plant uptake of free amino sugars in grassland soils

Amino sugars represent a major constituent of microbial cell walls (e.g. chitin, peptidoglycan) and they are present in large quantities in soil organic matter (SOM). The factors regulating their turnover in soil, however, are poorly understood. Here we investigated the turnover of glucosamine (GlcN) in comparison to glucose (Glc) and N-acetylglucosamine (GlcNAc) in two agricultural grassland soils. Over the range 0–1 mM, GlcN uptake occurred via a saturable high affinity transport systems reflecting its low solution concentrations and low rates of supply. In contrast, Glc uptake was characterised by a non-saturable much lower affinity transport system. Of the GlcN-derived carbon (C) taken into the biomass, ca. 90% was used for the production of new cell biomass rather than in respiration. Whilst temperature affected the uptake (Q₁₀ = 1.95) and mineralization (Q₁₀ = 2.32) of GlcN, it did not affect its C use efficiency within the microbial community. We calculated that the average annual flux of GlcN through the soil was 0.01–0.08 g C kg⁻¹ y⁻¹ which equated to 0.1–1.6% of total heterotrophic soil respiration. Microbial use of GlcN was significantly repressed in the presence of sugars (e.g. Glc, sucrose) and N-acetylglucosamine (GlcNAc). We ascribe this to competition at the transport level and due to internal catabolic repression of metabolic pathways involving GlcN within the microbial biomass. Maize (Zea mays L.) roots showed no capacity to take up exogenously applied GlcN at low external concentrations (10 μM) whilst GlcN was rhizotoxic at higher concentrations (EC₅₀ = 49 μM). This suggests that GlcN does not represent a significant source of dissolved organic nitrogen (DON) for plants. The presence of plants did indirectly, however, suppress the use of GlcN by the rhizosphere microbial community. Our work highlights the importance of GlcN in soil C and N cycling, however, we also raise concerns over its importance relative to that of GlcNAc which our evidence suggests plays a more prominent role in soil C and N cycling.     

Fungistatic and bacteriostatic activities of alkamides from Heliopsis longipes roots: affinin and reduced amides

This work demonstrates the fungistatic and bacteriostatic activities of affinin, the main alkamide of Heliopsis longipes (Gray) Blake (Asteraceae) roots and two alkamides obtained by catalytic reduction of affinin: N-isobutyl-2E-decenamide and N-isobutyl-decanamide. The bioactivity was tested against Rhizoctonia solani groups AG3 and AG5, Sclerotium rolfsii, Sclerotium cepivorum, Fusarium sp., Vertcillium sp., phytopathogenic fungi; Phytophthora infestans, a phytopathogenic Chromista; Saccharomyces cerevisiae, a nonphytopathogenic ascomycete; and Escherichia coli, Erwinia carotovora, and Bacillus subtilis, bacteria. Affinin, being the primary component of the lipidic fraction, is expected to be responsible for the fungitoxic activity observed in roots of this plant species. Four of the assayed fungi showed an important sensitivity to the presence of affinin: S. rolfsii, S. cepivorum, P. infestans, and R. solani AG-3 and AG-5, displaying a growth inhibition of 100%. S. cerevisiaeshowed a similar growth inhibition with affinin. None of the alkamides obtained by catalytic reduction of affinin showed a fungitoxic activity. Affinin had a definite negative effect on the growth of E. coli and B. subtilis, but E. carotovora carotovora was not sensitive to the highest dose of affinin assayed. N-Isobutyl-2E-decenamide displayed a higher bacteriostatic activity against E. coli and E. carotovora carotovora. In both cases, this alkamide was more potent than affinin. On the other hand, only N-isobutyl-decanamide displayed a significant activity on the growth of B. subtilis.     

Structural identification of novel oligosaccharides produced by Lactobacillus bulgaricus and Lactobacillus plantarum

β-Galactosidases (β-Gal) of lactic acid bacteria produce oligosaccharides from lactose when suitable acceptor carbohydrates are present. This study aimed to elucidate the structure of oligosaccharides formed by galactosylation of N-acetylglucosamine (GlcNAc) and fucose. Crude cellular extract of Lactobacillus bulgaricus and LacLM of Lactobacillus plantarum were used as sources of β-Gal activity. Disaccharides obtained by galactosylation of GlcNAc were identified as Gal-β-(1→4)-GlcNAc or Gal-β-(1→6)-GlcNAc by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and comparison with external standards. Trisaccharides were identified as Gal-β-(1→6)-Gal-β-(1→[4 or 6])-GlcNAc by LC-MS, analysis of the MS/MS spectra of selected in-source fragment ions, and their relative retention times. LC-MS analysis revealed the presence of five galactosylated fucosides, but their linkage type could not be identified, partly due to the lack of reference compounds. β-Gal of lactic acid bacteria may serve as suitable tools for the chemoenzymatic synthesis of therapeutic oligosaccharides.     

Isolation, characterization and antifungal activity of major constituents of the Himalayan lichen Parmelia reticulata Tayl

Antifungal activity of hexane, ethyl acetate and methanol extracts of Parmelia reticulata was evaluated against soilborne pathogenic fungi, namely, Sclerotium rolfsii, Rhizoctonia solani, R. bataticola, Fusarium udum, Pythium aphanidermatum and P. debaryanum by poisoned food technique. Maximum antifungal activity was exhibited by hexane and ethyl acetate extracts against most of the test pathogens. Secondary metabolites, namely, (±)-isousnic acid, (±)-protolichesterinic acid, atranorin, evernyl, ethyl hematommate, ethyl orsellinate, methyl hematommate (3-formyl-2,4-dihydroxy-6-methylbenzoic acid methyl ester), 2-hydroxy-4-methoxy-3,6-dimethylbenzoic acid, 1-hydroxy-3,6-dimethoxy-8-methyl-xanthen-9-one, baeomycesic acid and salazinic acid, were isolated from the above extracts and identified by 1H NMR, 13C NMR and mass spectroscopic methods. When these metabolites were tested for antifungal activity against test pathogens, maximum antifungal activity was exhibited by (±)-protolichesterinic acid against R. solani (ED50=23.09 μg mL(-1)) and P. debaryanum (ED50=16.07 μg mL(-1)) and by atranorin against S. rolfsii (ED50=39.70 μg mL(-1)). The antifungal activity of protolichesterinic acid was found to be comparable to that of hexaconazole, a commercial fungicide.     

Determination of glucosamine and N-acetyl glucosamine in fungal cell walls

A new method was developed to determine glucosamine (GlcN) and N-acetyl glucosamine (GlcNAc) in materials containing chitin and chitosan, such as fungal cell walls. It is based on two steps of hydrolysis with (i) concentrated sulfuric acid at low temperature and (ii) dilute sulfuric acid at high temperature, followed by one-step degradation with nitrous acid. In this process, chitin and chitosan are converted into anhydromannose and acetic acid. Anhydromannose represents the sum of GlcN and GlcNAc, whereas acetic acid is a marker for GlcNAc only. The method showed recovery of 90.1% of chitin and 85.7-92.4% of chitosan from commercial preparations. Furthermore, alkali insoluble material (AIM) from biomass of three strains of zygomycetes, Rhizopus oryzae, Mucor indicus, and Rhizomucor pusillus, was analyzed by this method. The glucosamine contents of AIM from R. oryzae and M. indicus were almost constant (41.7 +/- 2.2% and 42.0 +/- 1.7%, respectively), while in R. pusillus, it decreased from 40.0 to 30.0% during cultivation from 1 to 6 days. The GlcNAc content of AIM from R. oryzae and R. pusillus increased from 24.9 to 31.0% and from 36.3 to 50.8%, respectively, in 6 days, while it remained almost constant during the cultivation of M. indicus (23.5 +/- 0.8%).     

Viridenepoxydiol, a new pentasubstituted oxiranyldecene produced by Trichoderma viride

A new pentasubstituted oxiranyldecene, named viridenepoxydiol, has been isolated (0.9 mg/L) from the culture filtrate of a strain of Trichoderma viride showing in vitro and in vivo antagonistic activity against Sclerotium rolfsii, which is the causal agent of crown and stem rot of artichoke. Viridenepoxydiol was characterized as 3,5,9-trimethyl-2-oxiranyl-dec-8-ene-2,5-diol (3) using spectroscopic methods. It showed inhibitor effect on mycelial growth of S. rolfsii and its minimum inhibitory concentration (over 90% inhibition) was found to be 396 mug/mL. This is the first time that viridenepoxydiol was reported.     

Generation of thiols by biotransformation of cysteine-aldehyde conjugates with baker's yeast

Baker's yeast was shown to catalyze the transformation of cysteine-furfural conjugate into 2-furfurylthiol. The biotransformation's yield and kinetics were influenced by the reaction parameters such as pH, incubation mode (aerobic and anaerobic), and substrate concentration. 2-Furfurylthiol was obtained in an optimal 37% yield when cysteine-furfural conjugate at a 20 mM concentration was anaerobically incubated with whole cell baker's yeast at pH 8.0 and 30 degrees C. Similarly to 2-furfurylthiol, 5-methyl-2-furfurylthiol (11%), benzylthiol (8%), 2-thiophenemethanethiol (22%), 3-methyl-2-thiophenemethanethiol (3%), and 2-pyrrolemethanethiol (6%) were obtained from the corresponding cysteine-aldehyde conjugates by incubation with baker's yeast. This work indicates the versatile bioconversion capacity of baker's yeast for the generation of thiols from cysteine-aldehyde conjugates. Thanks to its food-grade character, baker's yeast provides a biochemical tool to produce thiols, which can be used as flavorings in foods and beverages.     

Volatile compounds emitted by sclerotia of Sclerotinia minor,Sclerotinia sclerotiorum,and Sclerotium rolfsii

Volatile compounds emitted by sclerotia of Sclerotinia minor, Sclerotinia sclerotiorum, and Sclerotium rolfsii were identified by solid phase microextraction followed by gas chromatography and mass spectometry. Both S. minor and S. sclerotiorum emitted 2-methylenebornane and 2-methylisoborneol. In addition, S. minor emitted mesityl oxide, gamma-butyrolactone, cis- and trans-linalool oxide, linalool, and trans-nerolidol. S. sclerotiorum emitted 2-methyl-2-bornene, 1-methylcamphene, and a diterpene with a molecular weight of 272. Sclerotium rolfsii did not emit any of these compounds but did emit delta-cadinene and cis-calamenene. Chemicals emitted by S. minor and S. sclerotiorum were tested to determine if they could stimulate germination of conidia of Sporidesmium sclerotivorum, a mycoparasite on sclerotia of Sclerotinia spp. Chemicals were tested at 1 part per billion to 100 parts per million, both in direct contact with conidia and near, but not in, physical contact. None of the chemicals alone nor a combination of all chemicals induced germination of conidia of S. sclerotivorum.     

Effect of Formulation and Processing Treatments on Viscosity and Solubility of Extractable Barley β‐Glucan in Bread Dough Evaluated Under In Vitro Conditions

β‐Glucan shows great potential for incorporation into bread due to its cholesterol lowering and blood glucose regulating effects, which are related to its viscosity. The effects of β‐glucan concentration, gluten addition, premixing, yeast addition, fermentation time, and inactivation of the flour enzymes on the viscosity of extractable β‐glucan following incorporation into a white bread dough were studied under physiological conditions, as well as, β‐glucan solubility in fermented and unfermented dough. β‐Glucan was extracted using an in vitro protocol designed to approximate human digestion and hot water extraction. The viscosity of extractable β‐glucan was not affected by gluten addition, the presence of yeast, or premixing. Fermentation produced lower (P ≤ 0.05) extract viscosity for the doughs with added β‐glucan, while inactivating the flour enzymes and increasing β‐glucan concentration in the absence of fermentation increased (P ≤ 0.05) viscosity. The physiological solubility of the β‐glucan concentrate (18.1%) and the β‐glucan in the unfermented dough (20.5%) were similar (P > 0.05), while fermentation substantially decreased (P ≤ 0.05) solubility to 8.7%, indicating that the reduction in viscosity due to fermentation may be highly dependent on solubility in addition to β‐glucan degradation. The results emphasize the importance of analyzing β‐glucan fortified foods under physiological conditions to identify the conditions in the dough system that decrease β‐glucan viscosity so that products with maximum functionality can be developed.     

An efficient method for the purification and characterization of nematicidal azadirachtins A,B, and H,using MPLC and ESIMS

Azadirachtin A enriched concentrate containing 60% active ingredient (a.i.) was prepared from the methanolic extract of the de-fatted neem (Azadirachta indica A. Juss) seed kernels. Azadirachtins A, B, and H, the three major bioactive constituents of neem seed kernel, were purified from this methanolic concentrate by employing reverse phase medium-pressure liquid chromatography (MPLC), using methanol-water solvent system as an eluant. The three pure azadirachtin congeners thus obtained were characterized by their unique mass spectral fragmentation, using electrospray probe in positive ion mode (ESI). All three azadirachtins exhibited nematicidal and antifungal activities. Azadirachtin B was the most effective against the reniform nematode Rotylenchulus reniformis (EC(50) 96.6 ppm), followed by Azadirachtin A (119.1 ppm) and H (141.2 ppm). At 200-ppm concentration, the test compounds caused 50-65% mortality of Caenorhabditis elegans nematode. Azadirachtin H showed the highest activity against the phytophagous fungi Rhizoctonia solani (EC(50) 63.7 ppm) and Sclerotium rolfsii (EC(50) 43.9 ppm), followed by B and A. The isolation of pure azadirachtins A, B, and H directly by MPLC purification from its concentrate and their characterization by ESIMS are unique and less time-consuming.     

Effects of chitin degradation products N-acetylglucosamine and N,Nʹ-diacetylchitobiose on chitinase activity and bacterial community structure in an incubated upland soil

ABSTRACT

Chitin, which is the polymer of N-acetylglucosamine (GlcNAc) linked by β1,4 glycoside bonds, has been reported as a soil amendment to mitigate plant soil diseases, increasing the population of chitin-degrading bacteria, and chitinolytic enzymatic activity in the soil. In some chitin-degrading bacteria, whose chitinolytic systems have been intensively studied, the chitin degradation product N,N?-diacetylchitobiose {(GlcNAc)₂} induces expression of genes for chitinases whereas GlcNAc does not. To evaluate the effects of these mono- and disaccharides on the population and activity of chitinolytic bacteria in soil, we investigated the chitinolytic enzyme activity and bacterial community structure in an incubated upland soil supplemented with GlcNAc or (GlcNAc)₂. The added GlcNAc and (GlcNAc)₂ (2 mg g^?1) were consumed within 1 d when incubated at 25°C. Chitinase activity was induced by (GlcNAc)₂ and chitin after 1-d and 7-d incubation, respectively, but not by GlcNAc. N-acetylglucosaminidase (GlcNAcase) activity was induced by GlcNAc but was lower than those by (GlcNAc)₂ and chitin. Amplicon sequencing analysis targeting 16S rRNA genes demonstrated that both GlcNAc and (GlcNAc)₂ significantly increased the rate of the order Bacillales, but the compositions of Bacillales differed from each other: the family Planococcaceae significantly increased in either GlcNAc- or (GlcNAc)₂-added soil, but the genera Bacillus and Paenibacillus were increased mainly by GlcNAc and (GlcNAc)₂, respectively. The family Streptomycetaceae of the order Actinomycetales was significantly increased by (GlcNAc)₂ and chitin, but GlcNAc did not. Thus, GlcNAc and (GlcNAc)₂, which were promptly consumed in the incubated soil, indicated partly similar but distinctive effects on chitinolytic enzyme activity and bacterial communities. Both aminosugars increased GlcNAcase activity and the population size of Planococcaceae. GlcNAc increased Bacillus. Chitinase activity and the populations of Paenibacillus and Streptomycetaceae, a number of strains of which are known as potent chitin-degraders, were increased by (GlcNAc)₂, but not by GlcNAc.     

Validation of antifreeze properties of glutathione based on its thermodynamic characteristics and protection of baker's yeast during cryopreservation

The antifreeze ability of glutathione was evaluated on the basis of its thermodynamic characteristics and protection of baker's yeast during cryopreservation at -30 degrees C. The thermodynamic characteristics and protection of baker's yeast of glutathione were similar to those of known antifreeze proteins, such as carrot antifreeze protein and holly antifreeze protein. These properties included lowering the freezing point at about 0.20 degrees C non-colligatively, decreasing freezable water content, controlling the movement of free water for its strong hydrophilicity, and improving baker's yeast survival during the simulated processing of frozen dough. Therefore, glutathione was viewed to be an antifreeze protein like substance on the basis of its unique thermodynamic characteristics and protection of baker's yeast. The method combining thermodynamic characteristic analysis and protection evaluation is a new and simple way to screen new antifreeze proteins.     

Physicochemical properties and bioactivity of fungal chitin and chitosan

Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation, and crystallinity and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in the mycelium of A. niger was 11.10% dw and in the mycelium of M. rouxii was 20.13% dw. On the basis of the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan, whereas A. niger contained only chitin. The yields of crude chitin from A. niger and M. rouxii were 24.01 and 13.25%, respectively, and the yield of chitosan from M. rouxii was 12.49%. Significant amounts (7.42-39.81%) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degrees of acetylation were determined to be 76.53 and 50.07% for chitin from A. niger and M. rouxii, respectively, and 19.5% for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intense than in corresponding materials from shrimp shells. The extracted chitin and chitosan in a concentration of 0.1% reduced Salmonella Typhimurium DT104 2576 counts by 0.5-1.5 logs during a 4 day incubation in tryptic soy broth at 25 degrees C. Furthermore, all tested chitinous materials from fungal sources significantly reduced lesions caused by Botrytis cinerea and Penicillium expansum in harvested apples.     

In vitro potential antioxidant activity of (1-->3),(1-->6)-beta-D-glucan and protein fractions from Saccharomyces cerevisiae cell walls

(1-->3),(1-->6)-Beta-D-Glucan, a cell wall polysaccharide in many microorganisms, fungi and algae, is a well-known biological response modifier. Recently, it was found that (1-->3)-beta-D-glucan from Saccharomyces cerevisiae also exhibits antioxidative capabilities. In this study the antioxidative activity of the cell wall fractions of brewer's yeast was investigated. Particular emphasis was put on the question to which extent glucan is responsible for the antioxidative activity of the cell walls and how the other cell wall components might contribute. For the experiments yeast cell walls from brewery fermentations were used. Glucan was isolated by a three-step extraction procedure including a combination of hot water and enzymatic treatment. The level of (1-->3),(1-->6)-beta-D-glucan in the cell walls was analyzed enzymatically. The antioxidant activity was determined by electron paramagnetic resonance spectrometry and Trolox equivalent antioxidant capacity assay. The results show that the antioxidative activity of yeast cell wall proteins exceeds that of beta-glucan greatly. Especially aromatic side chains and free thiols from denatured proteins seem to work as antioxidants.     

Effects of solarization of soil on nematode and fungal pathogens at two sites in victoria

The effect of covering soil with transparent polyethylene sheets, known as soil solarization, on the viability of plant pathogens was determined. The treatment was tested in mid-summer on sandy loams in N.W. and S. Victoria. Columns of moist soil were inoculated with one of a variety of pathogens, viz. Fusarium oxysporum, Pythium irregulare, Plasmodiophora brassicae, Sclerotium cepivorum, S. rolfsii, Sclerotinia minor, Verticillium dahliae and the nematodes Macroposthania xenoplax, Meloidogyne javanica, Pratylenchus penetrans and Tylenchulus semipenetrans. Columns were placed vertically in soil, and then treated either for 4 weeks in N.W. Victoria, or 6 weeks in S. Victoria.Preliminary laboratory tests showed that pathogens were killed by temperatures within the range 38–55°C. The relative sensitivities of pathogens to fluctuating soil temperatures were similar at both sites. The most sensitive were the nematodes, and the fungi V. dahliae, S. cepivorum and S. minor, while F. oxysporum, P. irregulare and P. brassicae were the least sensitive. In N.W. Victoria treatment effects were apparent to 26 cm and most pathogens were not recovered from 0 to 11 cm. In S. Victoria treatment effects were apparent to a depth of 16cm and most pathogens were not recovered from 0 to 6cm.     

Development of a simplified method for the determination of folates in baker's yeast by HPLC with ultraviolet and fluorescence detection

A simplified HPLC method for rapid determination of folates in yeast with ultraviolet and fluorescence detection without sample purification has been developed. By use of the column Aquasil C(18), specially designed for polar analytes, and gradient elution, it was possible to separate and determine five folate derivatives: tetrahydrofolate, 5-methyltetrahydrofolate, and 5-formyltetrahydrofolate with fluorescence detection, and 10-formylfolic acid and folic acid with ultraviolet detection. The sample preparation required only a small amount of dry yeast (25-50 mg) and included an extraction of folates by heat treatment and deconjugation of folate polyglutamates to monoglutamates with the use of rat serum conjugase. Validation involved investigation of matrix effects, determination of recovery by standard addition method, repeatability, and stability tests. The dominating folate forms in commercial dry baker's yeast were found to be tetrahydrafolate and 5-methyltetrahydrofolate with a total folate content of 2890 microg/100 g (63.4 nmol/g). The simplicity of the method makes it suitable for folate screening studies of different yeast strains.     

Stereospecificity of myo-inositol hexakisphosphate dephosphorylation by a phytate-degrading enzyme of baker's yeast

During food processing such as baking, phytate is dephosphorylated to produce degradation products, such as myo-inositol pentakis-, tetrakis-, tris-, bis-, and monophosphates. Certain myo-inositol phosphates have been proposed to have positive effects on human health. The position of the phosphate groups on the myo-inositol ring is thereby of great significance for their physiological functions. Using a combination of high-performance ion chromatography analysis and kinetic studies the stereospecificity of myo-inositol hexakisphosphate dephosphorylation by a phytate-degrading enzyme from baker's yeast (Saccharomyces cerevisiae) was established. The data demonstrate that the phytate-degrading enzyme from baker's yeast dephosphorylates myo-inositol hexakisphosphate in a stereospecific way by sequential removal of phosphate groups via D-Ins(1,2,4,5,6)P(5), D-Ins(1,2,5,6)P(4), D-Ins(1,2,6)P(3), D-Ins(1,2)P(2), to finally Ins(2)P (notation 3/4/5/6/1). Knowledge of the absolute stereochemical specificity of the baker's yeast phytase allows use of the enzyme to produce defined myo-inositol phosphates for kinetic and physiological studies.     

Variation in fatty acid composition of Artemia salina nauplii enriched with microalgae and baker's yeast for use in larviculture

The high content of the essential fatty acids in some microalgae and baker's yeast has made them excellent diets for boosting the fatty acid content of livefood Artemia. The influences of baker's yeast (Saccharomyces cerevisiae) and three microalgae, viz., Chlorella salina, Chaetoceros calcitrans, and Nannochloropsis salina, were tested as diet components in marine livefeed brine shrimp Artemia salina nauplii to improve the polyunsaturated fatty acid (PUFA) composition. Artemia nauplii submerged in these diets for four different enrichment intervals (3, 6, 8, and 24 h) were found to incorporate essential fatty acids, and the percentage composition of different fatty acids was measured in the enriched Artemia nauplii and enrichment diets. N. salina produced higher levels of arachidonic acid (AA, 20:4n6, 9.50%), eicosapentaenoic acid (EPA, 20:5n3, 25.80%), and docosahexaenoic acid (DHA, 22:6n3, 4.18%) as compared to other diets. The total PUFA content of the enriched Artemia by N. salina increased by 56.50% with enrichment periods up to 8 h, followed by a significant reduction in the final 24 h. N. salina yielded Artemia nauplii with considerable EPA (8.05%), AA (14.15%), and DHA (1.85%) after 8 h of enrichment, which are significantly higher levels than in nauplii fed with the other three diets (p = 0.05). The DHA/EPA values in Artemia enriched for 6 h by N. salina and C. calcitrans were found to be, respectively, 88.46 and 25% higher than freshly hatched Artemia. Artemia enriched by C. salina and baker's yeast exhibited a reduction in PUFA content even at 6 h of enrichment. Significant relative decreases in DHA, EPA, and total PUFA in Artemia enriched with all of the diets were apparent, with a corresponding increase in the total saturated fatty acid content (26.95 +/- 9.75%) in the final stages (24 h) of enrichment (p = 0.05).