Influence of ammonium sulphate feeding time on fed-batch Arthrospira (Spirulina) platensis cultivation and biomass composition with and without pH control

Previous work demonstrated that a mixture of NH₄Cl and KNO₃ as nitrogen source was beneficial to fed-batch Arthrospira (Spirulina) platensis cultivation, in terms of either lower costs or higher cell concentration. On the basis of those results, this study focused on the use of a cheaper nitrogen source mixture, namely (NH₄)₂SO₄ plus NaNO₃, varying the ammonium feeding time (T = 7-15 days), either controlling the pH by CO₂ addition or not. A. platensis was cultivated in mini-tanks at 30 °C, 156 μmol photons m⁻² s⁻¹, and starting cell concentration of 400 mg L⁻¹, on a modified Schlösser medium. T = 13 days under pH control were selected as optimum conditions, ensuring the best results in terms of biomass production (maximum cell concentration of 2911 mg L⁻¹, cell productivity of 179 mg L⁻¹ d⁻¹ and specific growth rate of 0.77 d⁻¹) and satisfactory protein and lipid contents (around 30% each).     

Repellent activity of catmint, Nepeta cataria, and iridoid nepetalactone isomers against Afro-tropical mosquitoes, ixodid ticks and red poultry mites

The repellent activity of the essential oil of the catmint plant, Nepeta cataria (Lamiaceae), and the main iridoid compounds (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone, was assessed against (i) major Afro-tropical pathogen vector mosquitoes, i.e. the malaria mosquito, Anopheles gambiae s.s. and the Southern house mosquito, Culex quinquefasciatus, using a World Health Organisation (WHO)-approved topical application bioassay (ii) the brown ear tick, Rhipicephalus appendiculatus, using a climbing repellency assay, and (iii) the red poultry mite, Dermanyssus gallinae, using field trapping experiments. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analysis of two N. cataria chemotypes (A and B) used in the repellency assays showed that (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone were present in different proportions, with one of the oils (from chemotype A) being dominated by the (4aS,7S,7aR) isomer (91.95% by GC), and the other oil (from chemotype B) containing the two (4aS,7S,7aR) and (4aS,7S,7aS) isomers in 16.98% and 69.83% (by GC), respectively. The sesquiterpene hydrocarbon (E)-(1R,9S)-caryophyllene was identified as the only other major component in the oils (8.05% and 13.19% by GC, respectively). Using the topical application bioassay, the oils showed high repellent activity (chemotype A RD₅₀ = 0.081 mg cm⁻² and chemotype B RD₅₀ = 0.091 mg cm⁻²) for An. gambiae comparable with the synthetic repellent DEET (RD₅₀ = 0.12 mg cm⁻²), whilst for Cx. quinquefasciatus, lower repellent activity was recorded (chemotype A RD₅₀ = 0.34 mg cm⁻² and chemotype B RD₅₀ = 0.074 mg cm⁻²). Further repellency testing against An. gambiae using the purified (4aS,7S,7aR) and (4aS,7S,7aS)-nepetalactone isomers revealed overall lower repellent activity, compared to the chemotype A and B oils. Testing of binary mixtures of the (4aS,7S,7aR) and (4aS,7S,7aS) isomers across a range of ratios, but all at the same overall dose (0.1 mg), revealed not only a synergistic effect between the two, but also a surprising ratio-dependent effect, with lower activity for the pure isomers and equivalent or near-equivalent mixtures, but higher activity for non-equivalent ratios. Furthermore, a binary mixture of (4aS,7S,7aR) and (4aS,7S,7aS) isomers, in a ratio equivalent to that found in chemotype B oil, was less repellent than the oil itself, when tested at two doses equivalent to 0.1 and 0.01 mg chemotype B oil. The three-component blend including (E)-(1R,9S)-caryophyllene at the level found in chemotype B oil had the same activity as chemotype B oil. In a tick climbing repellency assay using R. appendiculatus, the oils showed high repellent activity comparable with data for other repellent essential oils (chemotype A RD₅₀ = 0.005 mg and chemotype B RD₅₀ = 0.0012 mg). In field trapping assays with D. gallinae, addition of the chemotype A and B oils, and a combination of the two, to traps pre-conditioned with D. gallinae, all resulted in a significant reduction of D. gallinae trap capture. In summary, these data suggest that although the nepetalactone isomers have the potential to be used in human and livestock protection against major pathogen vectors, intact, i.e. unfractionated, Nepeta spp. oils offer potentially greater protection, due to the presence of both nepetalactone isomers and other components such as (E)-(1R,9S)-caryophyllene.     

Bicarbonate use in three aquatic plants

Our study aimed to test the ability of aquatic plants to use bicarbonate when acclimated to three different bicarbonate concentrations. To this end, we performed experiments with the three species Ceratophyllum demersum, Egeria densa, Lagarosiphon major to determine photosynthetic rates under varying bicarbonate concentrations. We measured bicarbonate use efficiency, photosynthetic performance and respiration. For all species, our results revealed that photosynthetic rates were highest in replicates grown at low alkalinity. Thus, E. densa had approx. five times higher rates at low (264 ± 15 μmol O₂ g⁻¹ DW h⁻¹) than at high alkalinity (50 ± 27 μmol O₂ g⁻¹ DW h⁻¹), C. demersum had three times higher rates (336 ± 95 and 120 ± 31 μmol O₂ g⁻¹ DW h⁻¹), and L. major doubled its rates at low alkalinity (634 ± 114 and 322 ± 119 μmol O₂ g⁻¹ DW h⁻¹). Similar results were obtained for bicarbonate use efficiency by E. densa (136 ± 44 and 43 ± 10 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹) and L. major (244 ± 29 and 82 ± 24 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹). As to C. demersum, efficiency was high but unaffected by alkalinity, indicating high adaptation ability to varied alkalinities. A pH drift experiment supported these results. Overall, our results suggest that the three globally widespread worldwide species of our study adapt to low inorganic carbon availability by increasing their efficiency of bicarbonate use.     

Short term effects of hypoxia and bioturbation on solute fluxes, denitrification and buffering capacity in a shallow dystrophic pond

The effects of short term hypoxia on bioturbation activity and inherent solute fluxes are scarcely investigated even if increasing number of coastal areas are subjected to transient oxygen deficits. In this work dark fluxes of oxygen (O₂), dissolved inorganic carbon (TCO₂) and nutrients across the sediment-water interface, as well as rates of denitrification (isotope pairing), were measured in intact sediment cores collected from the dystrophic pond of Sali e Pauli (Sardinia, Italy). Sediments were incubated at 100, 70, 40 and 10% of O₂ saturation in the overlying water, with both natural benthic communities, dominated by the polychaete Polydora ciliata (11.100 ± 2.500  ind. m^− 2), and after the addition of individuals of the deep-burrower polychaete Hediste diversicolor. Below an uppermost oxic layer of ~ 1 mm, sediments were highly reduced, with up to 6 mM of S²⁻ in the 5 mm layer. Flux of S²⁻ and O₂ calculated from pore water gradients were 8.61 ± 1.12 and − 2.27 ± 0.56 mmol m^− 2 h^− 1, respectively. However, sediment oxygen demand (SOD) calculated from core incubation was − 10.52 ± 0.33 mmol m^− 2 h^− 1, suggesting a major contribution of P. ciliata to O₂-mediated sulphide oxidation. P. ciliata also strongly stimulated NH₄⁺ and PO₄³⁻ fluxes, with rates ~ 15 and ~ 30 folds higher, respectively, than those estimated from pore water gradients. P. ciliata activity was significantly reduced at 10% O₂ saturation, coupled to decreased rates of solutes transfer. The addition of H. diversicolor further stimulated SOD, NH₄⁺ efflux and SiO₂ mobilisation. Similarly to P. ciliata, the degree of stimulation of SOD and NH₄⁺ flux by H. diversicolor depended on the level of oxygen saturation. TCO₂ regeneration, respiratory quotients, PO₄³⁻ fluxes and denitrification of added ¹⁵NO₃⁻ were not affected by the addition of H. diversicolor, but depended upon the O₂ levels in the water column. Denitrification rates supported by water column ¹⁴NO₃⁻ and sedimentary nitrification were both negligible (< 0.5 µmol m^− 2 h^− 1). They were not significantly affected by oxygen saturation nor by bioturbation, probably due to the limited availability of NO₃⁻ in the water column (< 3 µM) and O₂ in the sediments. This study demonstrates for the first time the integrated short term effect of transient hypoxia and bioturbation on solute fluxes across the sediment-water interface within a simplified lagoonal benthic community.     

Structural characterization of trace stilbene glycosides in Lysidice brevicalyx Wei using liquid chromatography/diode-array detection/electrospray ionization tandem mass spectrometry

The mass fragmentation patterns of stilbene glycosides isolated from the genus Lysidice were investigated by negative ion electrospray ionization tandem mass spectrometry, and the influence of collision energy on their fragmentation behavior is discussed. It is found that the presence of the Y₀⁻ and B₀⁻ ions in the MS² spectra is characteristic for 1 → 6 linked diglycosyl stilbenes, while the Y₀⁻, Y₁⁻, and Z₁⁻ ions are representative ions of 1 → 2 linked diglycosyl stilbenes. These results indicate that ESI-MSⁿ in the negative ion mode can be used to differentiate 1 → 6 and 1 → 2 linked diglycosyl stilbenes. Based on the fragmentation rules, 9 new trace constituents were identified or tentatively characterized in a fraction of Lysidice brevicalyx by using HPLC/HRMS and HPLC-DAD/ESI-MSⁿ. The results of the present study can assist in on-line structural identification of analogous constituents and targeted isolation of novel compounds from crude plant extracts.     

Vermistabilization of primary sewage sludge

An integrated composting-vermicomposting process has been developed for utilization of primary sewage sludge (PSS). Matured vermicompost was used as bulking material and a source of active microbial culture during aerobic activated composting (AAC). AAC resulted in sufficient enrichment of bulking material with organic matter after 20 cycles of recycling and mixing with PSS and produced materials acceptable for vermicomposting. Vermicomposting caused significant reduction in pH, volatile solids (VS), specific oxygen uptake rate (SOUR), total organic carbon (TOC), C/N ratio and pathogens and substantial increase in electrical conductivity (EC), total nitrogen (TN) and total phosphorous (TP) as compared to compost. Environmental conditions and stocking density have profound effects on vermicomposting. Temperature of 20 °C with high humidity is favorable environmental condition for vermicomposting employing Eisenia fetida. Favorable stocking density range for vermiculture is 0.5-2.0 kg m⁻² (optimum: 0.5 kg m⁻²) and for vermicomposting is 2.0-4.0 kg m⁻² (optimum: 3.0 kg m⁻²), respectively.     

Different sensitivity of Phragmites australis and Glyceria maxima to high availability of ammonium-N

The ability to cope with NH₄⁺-N was studied in the littoral helophytes Phragmites australis and Glyceria maxima, species commonly occupying fertile habitats rich in NH₄⁺ and often used in artificial wetlands. In the present study, Glyceria growth rate was reduced by 16% at 179 μM NH₄⁺-N, and the biomass production was reduced by 47% at 3700 μM NH₄⁺-N compared to NO₃⁻-N. Similar responses were not found in Phragmites. The amounts (mg g⁻¹ dry wt) of starch and total non-structural carbohydrates (TNC) in rhizomes were significantly lower in NH₄⁺ (8.9; 12.2 starch; 20.1; 41.9 TNC) compared to NO₃⁻ treated plants (28.0; 15.6 starch; 58.5; 56.3 TNC) in Phragmites and Glyceria, respectively. In addition, Glyceria showed lower amounts (mg g⁻¹ dry wt) of soluble sugars, TNC, K⁺, and Mg²⁺ in roots under NH₄⁺ (5.6; 14.3; 20.6; 1.9) compared to NO₃⁻ nutrition (11.6; 19.9; 37.9; 2.9, for soluble sugars, TNC, K⁺, and Mg²⁺, respectively), while root internal levels of NH₄⁺ and Ca²⁺ (0.29; 4.6 mg g⁻¹ dry wt, mean of both treatments) were only slightly affected. In Phragmites, no changes in soluble sugars, TNC, Ca²⁺, K⁺, and Mg²⁺ contents of roots (7.3; 14.9; 5.1; 17.3; 2.6 mg g⁻¹ dry wt, means of both treatments) were found in response to treatments. The results, therefore, indicate a more pronounced tolerance towards high NH₄⁺ supply in Phragmites compared to Glyceria, although the former may be susceptible to starch exhaustion in NH₄⁺-N nutrition. In contrast, Glyceria's ability to colonize fertile habitats rich in NH₄⁺ is probably related to the avoidance strategy due to shallow rooting or to the previously described ability to cope with high NH₄⁺ levels when P availability is high and NO₃⁻ is also provided.     

Solid-state fermentation of agro-industrial wastes to produce bioorganic fertilizer for the biocontrol of Fusarium wilt of cucumber in continuously cropped soil

Agro-industrial wastes of cattle dung, vinegar-production residue and rice straw were solid-state fermented by inoculation with Trichoderma harzianum SQR-T037 (SQR-T037) for production of bioorganic fertilizers containing SQR-T037 and 6-pentyl-α-pyrone (6PAP) to control Fusarium wilt of cucumber in a continuously cropped soil. Fermentation days, temperature, inoculum and vinegar-production residue demonstrated significant effects on the SQR-T037 biomass and the yield of 6PAP, based on fractional factorial design. Three optimum conditions for producing the maximum SQR-T037 biomass and 6PAP yield were predicted by central composite design and validated. Bioorganic fertilizer containing 8.46 log₁₀ ITS copies g⁻¹ dry weight of SQR-T037 and 1291.73 mg kg⁻¹ dry weight of 6PAP, and having the highest (p < 0.05) biocontrol efficacy, was achieved at 36.7 fermentation days, 25.9 °C temperature, 7.6% inoculum content, 41.0% vinegar-production residue, 20.0% rice straw and 39.0% cattle dung. This is a way to offer a high value-added use for agro-industrial wastes.     

Purification and characterization of two extracellular endochitinases from Massilia timonae

Two extracellular chitinases (designated as Chi-56 and Chi-64) produced by Massilia timonae were purified by ion-exchange chromatography, ammonium sulfate precipitation, and gel-filtration chromatography. The molecular mass of Chi-56 was 56 kDa as determined by both SDS-PAGE and gel-filtration chromatography. On the other hand, Chi-64 showed a molecular mass of 64 kDa by SDS-PAGE and 28 kDa by gel-filtration chromatography suggesting that its properties may be different from those of Chi-56. The optimum temperature, optimum pH, pI, K_m, and V_max of Chi-56 were 55 °C, pH 5.0, pH 8.5, 1.1 mg mL⁻¹, and 0.59 μmol μg⁻¹ h⁻¹, respectively. For Chi-64, these values were 60 °C, pH 5.0, pH 8.5, 1.3 mg mL⁻¹, and 1.36 μmol μg⁻¹ h⁻¹, respectively. Both enzymes were stimulated by Mn²⁺ and inhibited by Hg²⁺, and neither showed exochitinase activity. The N-terminal sequences of Chi-56 and Chi-64 were determined to be Q-T-P-T-Y-T-A-T-L and Q-A-D-F-P-A-P-A-E, respectively.     

The use of Fourier transform infrared spectroscopy to assay for urease from Pseudomonas aeruginosa and Canavalia ensiformis

A novel assay method was investigated for urease (EC 3.5.1.5) from Pseudomonas aeruginosa and Canavalia ensiformis by Fourier transform infrared spectroscopy. This enzyme catalyzed the hydrolysis of urea in phosphate buffer in deuterium oxide (²H₂O). The intensities of the bicarbonate bands maxima at 1625 and 1365 cm⁻¹ and of the amide I band at 1605 cm⁻¹ were measured as a function of time to study the kinetics of urea hydrolysis. The extinction coefficients ε of urea and bicarbonate were determined to be 0.72, 0.48, and 0.56 mM⁻¹ cm⁻¹ at 1625, 1605, and 1365 cm⁻¹, respectively. The initial velocity is proportional to the enzyme concentration by using the ureases from both C.ensiformis and P. aeruginosa. The kinetic constants (V_max, K_m, and K_cat) determined by Lineweaver-Burk plot were 532.2  U mg⁻¹ protein, 6.4 mM, and 806.36 s⁻¹, respectively. These data are in agreement with the results obtained by a spectrophotometric method using a linked assay based on glutamate dehydrogenase in aqueous media. Therefore, this spectroscopic method is highly suited to assay for urease activity and its kinetic parameters by using either cell-free extracts or purified enzyme preparations with an additional advantage of performing a real-time measurement of urease activity.     

Determination of the membrane permeability characteristics of Pacific oyster, Crassostrea gigas, oocytes and development of optimized methods to add and remove ethylene glycol

In order for cryopreservation to become a practical tool for aquaculture, optimized protocols must be developed for each species and cell type. Knowledge of a cell’s osmotic tolerance and membrane permeability characteristics can assist in optimized protocol development. In this study, these characteristics were determined for Pacific oyster oocytes and modified methods for loading and unloading ethylene glycol (EG) were tested. Oocytes were found to behave as ideal osmometers and their osmotically inactive fraction (V_b) was calculated to be 0.48. Oocytes exposed to NaCl solutions of 0.6 to 2.3 Osm fertilized at rates equivalent to oocytes left in seawater. This corresponds to volume changes of +27.3 and −38.1 ± 1.2%. The permeability of the oocytes to water (L_p) was determined to be 3.8 ± 0.4 × 10⁻², 5.7 ± 0.8 × 10⁻², and 13.2 ± 1.3 × 10⁻² μm min⁻¹ atm⁻¹, when measured at temperatures of 5, 10 and 20 °C. The respective EG permeability values (P_s) were 9.5 ± 0.1 × 10⁻⁵, 14.6 ± 1.2 × 10⁻⁵, and 41.7 ± 2.4 × 10⁻⁵ cm min⁻¹. The activation energies for L_p and P_s were determined to be 14.5 and 17.5 kcal mol⁻¹, respectively. Different models for EG loading and unloading from oocytes were developed and tested. Post-thaw fertilization did not differ significantly between a published step addition method and single step addition at 20 °C. This represents a considerable reduction in handling. The results of this study demonstrate that the cryobiological characteristics of a given cell type should be taken into account when developing cryopreservation methods.     

Effects of eutrophic water flooding on nitrate concentrations in mine wastes

Salt marshes near urban, industrial and mining areas are often affected both by heavy metals and by eutrophic water. The aim of this study was to assess and evaluate the main processes involved in the decrease of nitrate concentration in pore water of mine wastes flooded with eutrophic water, considering the presence or absence of plant rhizhosphere. Basic (pH ∼ 7.8) carbonated loam mine wastes and free-carbonated acidic (pH ∼ 6.2) sandy-loam mine wastes were collected from polluted coastal salt marshes of SE Spain which regularly receive nutrient-enriched water. The wastes were put in pots and flooded for 15 weeks with eutrophic water (dissolved organic carbon ∼26 mg L⁻¹, PO₄³⁻ ∼23 mg L⁻¹, NO₃⁻ ∼180 mg L⁻¹). Three treatments were assayed for each type of waste: pots with Sarcocornia fruticosa, pots with Phragmites australis and unvegetated pots. Soluble organic carbon, nitrate, soluble Cd, Pb and Zn, pH and Eh were monitored. But the 2nd day of flooding, nitrate concentrations had decreased between 70% and 90% (equivalent to 1.01-1.12 g N-NO₃⁻ m⁻² day⁻¹) with respect to the content in the water used for flooding, except in unvegetated pots with acidic wastes. Denitrification was the main mechanism associated with the removal of nitrate. The role of vegetation in improving the rhizospheric environment was relevant in the acidic wastes because higher sand content, lower pH and higher soluble metal concentrations might strongly hinder microbial activity Hence, revegetation of salt marshes polluted by acidic sandy mining wastes might improve the capacity of this type of environment to act as a green filter against excessive nitrate contents flowing through them.     

Ecology of aquatic Ranunculus communities under the Mediterranean climate

The Iberian Peninsula encompasses more than 80% of the species richness of European aquatic ranunculi. The floristic diversity of the phytocoenosis characterised by aquatic Ranunculus and the main physical–chemical factors of the water were studied in 43 localities of the central Iberian Peninsula. Four aquatic Ranunculus communities are found in most of the aquatic environments. These are species-poor and have an uneven distribution: three species of Batrachium are heterophyllous and their communities are distributed in different aquatic ecosystems on silicated substrates; one species is homophyllous and its community occurs in various aquatic ecosystems with carbonated waters. In the Mediterranean climate, Ranunculus species are present in different habitats, as shown by the results of all the statistical analyses. Ranunculus trichophyllus communities occur in base-rich waters with a high buffering capacity (2273.44 ± 794.57 mg CaCO₃ L⁻¹) and a high concentration of cations (Ca²⁺, 121 ± 33.12 mg L⁻¹; Mg²⁺, 71.64 ± 82.77 mg L⁻¹), nitrates (2.89 ± 4.80 mg L⁻¹), ammonium (2.19 ± 1.36 mg L⁻¹) and sulphates (216.25 ± 218.54 mg L⁻¹). Ranunculus penicillatus communities are found in flowing waters with a high concentration of phosphates (0.48 ± 0.6 mg L⁻¹) and intermediate buffering capacity (683.66 ± 446.76 mg CaCO₃ L⁻¹). Both Ranunculus pseudofluitans and Ranunculus peltatus communities grow in waters with low buffering capacity (R. pseudofluitans, 385.91 ± 209.2 mg CaCO₃ L⁻¹; R. peltatus, 263.3 ± 180.36 mg CaCO₃ L⁻¹), and a low concentration of cations (R. pseudofluitans: Ca²⁺, 12.57 ± 9.42 mg L⁻¹; Mg²⁺, 3.42 ± 1.67 mg L⁻¹; R. peltatus: Ca²⁺, 15 ± 18.26 mg L⁻¹; Mg²⁺, 6.26 ± 8.89 mg L⁻¹) and nutrients (R. pseudofluitans: nitrates, 0.23 ± 0.2 mg L⁻¹; phosphates, 0.09 ± 0.1 mg L⁻¹; R. peltatus: nitrates, 0.19 ± 0.21 mg L⁻¹; phosphates, 0.09 ± 0.12 mg L⁻¹); the first in flowing waters, the latter in still waters.     

Influences of light and UV-B on growth and sporulation of the green alga Ulva pertusa Kjellman

The cosmopolitan presence of Ulva spp. is partly due to its great reproductive ability, but relatively little information is available for the radiation conditions triggering reproduction. In the present study, we investigated the effect of photon irradiance, photoperiod, and spectral qualities of light on growth and reproduction of Ulva pertusa.During 8-day culture of discs cut from marginal parts of the thallus of U. pertusa, the size of the thallus discs was greatest at 10 μmol m⁻² s⁻¹, while saturation of reproduction occurred at 30 μmol m⁻² s⁻¹. The minimum photon irradiance allowing growth and reproduction was 5 and 10 μmol m⁻² s⁻¹, respectively. Rapid increases in the size and subsequent initiation of sporulation were observed in samples transferred to saturating irradiance from 5 μmol m⁻² s⁻¹ or darkness for 9 days. When exposed to different photoperiods (8:16-, 12:12-, 16:8-h LD and continuous light regimes) combined with different photon irradiances (10 and 100 μmol m⁻² s⁻¹), U. pertusa thallus showed that the thallus size attained at the low irradiance was similar in daylengths longer than 12 h per day, while the surface area increased in parallel with increasing light duration at the high irradiance. The degree of sporulation at 10 μmol m⁻² s⁻¹ varied, ranging from no sporulation in 8:16-h LD to 80% in 16:8-h LD and continuous light. On the other hand, there was no remarkable difference in the degree of sporulation between the photoperiods except for slightly smaller percentage sporulation in 8:16-h LD at 100 μmol m⁻² s⁻¹.At 5 μmol m⁻² s⁻¹, the growth of U. pertusa was markedly lower in green than in blue or red light, but there was no sporulation in any spectral quality. The degree of sporulation at 20 μmol m⁻² s⁻¹ was almost twice as much in blue or red as in green light.The size of plants irradiated with 1.0 W m⁻² of UV-B for 20-40 min increased by 18-21% relative to control, whereas higher UV irradiance caused inhibition of growth. There was a significantly lower incidence of sporulation in UV-B-irradiated plants with the degree of reduction being greater in those exposed to higher UV doses. The total biologically effective UV-B dose for 50% inhibition of sporulation was 0.085 Dose_eff kJ m⁻². The time required to achieve 50% inhibition would be longer than 13 h at depths below 1 m in Ahnin coastal waters. The vertical attenuation coefficient of PAR (λ=400-700 nm) and UV-B (λ=300-320 nm) in April 1998 at Ahnin on the eastern coast of Korea was 0.21 m⁻¹ for K_PAR and 0.54 m⁻¹ for K_UV-B. A large reduction of light quantity and rapid disappearance of blue wavelength occurred by shading from overlying thalli.Percentage inhibition of sporulation was only 14-18% at 150-200 μmol m⁻² s⁻¹ compared with 70% at 10 μmol m⁻² s⁻¹, when plants were incubated under different irradiances of PAR immediately after UV-B exposures.These different photoadaptive strategies for sporulation may in part account for the great ecological success of U. pertusa.     

Responses of Gmelina arborea, a tropical deciduous tree species, to elevated atmospheric CO2: Growth, biomass productivity and carbon sequestration efficacy

The photosynthetic response of trees to rising CO₂ concentrations largely depends on source-sink relations, in addition to differences in responsiveness by species, genotype, and functional group. Previous studies on elevated CO₂ responses in trees have either doubled the gas concentration (>700 μmol mol⁻¹) or used single large addition of CO₂ (500-600 μmol mol⁻¹). In this study, Gmelina arborea, a fast growing tropical deciduous tree species, was selected to determine the photosynthetic efficiency, growth response and overall source-sink relations under near elevated atmospheric CO₂ concentration (460 μmol mol⁻¹). Net photosynthetic rate of Gmelina was ∼30% higher in plants grown in elevated CO₂ compared with ambient CO₂-grown plants. The elevated CO₂ concentration also had significant effect on photochemical and biochemical capacities evidenced by changes in F_V/F_M, ABS/CSm, ET₀/CSm and RuBPcase activity. The study also revealed that elevated CO₂ conditions significantly increased absolute growth rate, above ground biomass and carbon sequestration potential in Gmelina which sequestered ∼2100 g tree⁻¹ carbon after 120 days of treatment when compared to ambient CO₂-grown plants. Our data indicate that young Gmelina could accumulate significant biomass and escape acclimatory down-regulation of photosynthesis due to high source-sink capacity even with an increase of 100 μmol mol⁻¹ CO₂.     

Metal biosorption by two cyanobacterial mats in relation to pH, biomass concentration, pretreatment and reuse

The pH-dependent metal sorption by Oscillatoria- and Phormidium-dominated mats was effectively expressed by the Hill function. The estimated Hill functions can fruitfully predict the amount of metal sorbed at a particular initial pH. Pretreatment of biomass with 0.1 mmol L⁻¹ HCl was more effective than pretreatment with CaCl₂, HNO₃, NaOH, and SDS in enhancing metal sorption ability of the biomass. Desorption of metal ions in the presence of 100 mmol L⁻¹ HCl from metal-loaded mat biomass was completed within 1 h. After six cycles of metal sorption/desorption, sorption decreased by 6-15%. Only 6% and 11% of the biomass derived from the Oscillatoria sp.- and Phormidium sp.-dominated mats was lost during the cycling. The cyanobacterial mats seem to have better potential than several biomass types for use in metal sorption from wastewaters as they are ubiquitous, self-immobilized, and have good reusability.     

Vertical tubular photobioreactor for semicontinuous culture of Cyanobium sp

We evaluated the kinetic culture characteristics of the microalgae Cyanobium sp. grown in vertical tubular photobioreactor in semicontinuous mode. Cultivation was carried out in vertical tubular photobioreactor for 2 L, in 57 d, at 30 °C, 3200 Lux, and 12 h light/dark photoperiod. The maximum specific growth rate was found as 0.127 d⁻¹, when the culture had blend concentration of 1.0 g L⁻¹, renewal rate of 50%, and sodium bicarbonate concentration of 1.0 g L⁻¹. The maximum values of productivity (0.071 g L⁻¹ d⁻¹) and number of cycles (10) were observed in blend concentration of 1.0 g L⁻¹, renewal rate of 30%, and bicarbonate concentration of 1.0 g L⁻¹. The results showed the potential of semicontinuous cultivation of Cyanobium sp. in closed tubular bioreactor, combining factors such as blend concentration, renewal rate, and sodium bicarbonate concentration.     

An unusual thermostable aspartic protease from the latex of Ficus racemosa (L.)

The most extensively studied ficins have been isolated from the latex of Ficus glabrata and Ficus carica. However the proteases (ficins) from other species are less known. The purification and characterization of a protease from the latex of Ficus racemosa is reported. The enzyme purified to homogeneity is a single polypeptide chain of molecular weight of 44,500 ± 500 Da as determined by MALDI-TOF. The enzyme exhibited a broad spectrum of pH optima between pH 4.5-6.5 and showed maximum activity at 60 ± 0.5 °C. The enzyme activity was completely inhibited by pepstatin-A indicating that the purified enzyme is an aspartic protease. Far-UV circular dichroic spectra revealed that the purified enzyme contains predominantly β-structures. The purified protease is thermostable. The apparent T_m, (mid point of thermal inactivation) was found to be 70 ± 0.5 °C. Thermal inactivation was found to follow first order kinetics at pH 5.5. Activation energy (E_a) was found to be 44.0 ± 0.3 kcal mol⁻¹. The activation enthalpy (ΔH^∗), free energy change (ΔG^∗) and entropy (ΔS^∗) were estimated to be 43 ± 4 kcal mol⁻¹, −26 ± 3 kcal mol⁻¹ and 204 ± 10 cal mol⁻¹ K⁻¹, respectively. Its enzymatic specificity studied using oxidized B chain of insulin indicates that the protease preferably hydrolyzed peptide bonds C-terminal to glutamate, leucine and phenylalanine (at P₁ position). The broad specificity, pH optima and elevated thermal stability indicate the protease is distinct from other known ficins and would find applications in many sectors for its unique properties.     

Larsenia salina gen. nov., sp. nov., a new member of the family Halomonadaceae based on multilocus sequence analysis

Two Gram-staining-negative, moderately halophilic bacteria, strains M1-18^T and L1-16, were isolated from a saltern located in Huelva (Spain). They were motile, strictly aerobic rods, growing in the presence of 3–25% (w/v) NaCl (optimal growth at 7.5–10% [w/v] NaCl), between pH 4.0 and 9.0 (optimal at pH 6.0–7.0) and at temperatures between 15 and 40 °C (optimal at 37 °C). Phylogenetic analysis based on 16S rRNA gene sequence comparison showed that both strains showed the higher similarity values with Chromohalobacter israelensis ATCC 43985^T (95.2–94.8%) and Chromohalobacter salexigens DSM 3043^T (95.0–94.9%), and similarity values lower than 94.6% with other species of the genera Chromohalobacter, Kushneria, Cobetia or Halomonas. Multilocus sequence analysis (MLSA) based on the partial sequences of atpA, rpoD and secA housekeeping genes indicated that the new isolates formed an independent and monophyletic branch that was related to the peripheral genera of the family Halomonadaceae, Halotalea, Carnimonas and Zymobacter, supporting their placement as a new genus of the Halomonadaceae. The DNA–DNA hybridization between both strains was 82%, whereas the values between strain M1-18^T and the most closely related species of Chromohalobacter and Kushneria were equal or lower to 48%. The major cellular fatty acids were C_18:1ω7c/C_18:1ω6c, C_16:0, and C_16:1ω7c/C_16:1ω6c, a profile that differentiate this new taxon from species of the related genera. We propose the placement of both strains as a novel genus and species, within the family Halomonadaceae, with the name Larsenia salina gen. nov., sp. nov. The type strain is M1-18^T (= CCM 8464 = CECT 8192^T = IBRC-M 10767^T = LMG 27461^T).     

Structural characterization and protective effect against murine sepsis of fucogalactans from Agaricus bisporus and Lactarius rufus

Fucogalactans from edible Agaricus bisporus (RFP-Ab) and wild Lactarius rufus (RFP-Lr) mushrooms were obtained on aqueous extraction followed by purification. RFP-Ab had M_w 43.8 × 10⁴ g mol⁻¹ and RFP-Lr M_w 1.4 × 10⁴ g mol⁻¹. RFP-Lr had a (1 → 6)-linked α-d-Galp main-chain partially substituted at O-2 by nonreducing end-units of α-l-Fucp (29%). While RFP-Ab had a similar main chain, it was partially substituted at O-2 by nonreducing end-units of α-l-Fucp (2.8%) and β-d-Galp (14.5%), and partially methylated at HO-3. Both RFP-Lr and RFP-Ab were tested in mice against polymicrobial sepsis. Lethality rate, myeloperoxidase (MPO) activity and cytokine levels were determined. It was observed a reduction in late mortality rate by 62.5% and 50%, respectively, prevention of neutrophil accumulation in ileum and decreasing in TNF-α and IL-1β serum levels.