Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Laboratory experiments on the effects of variable suspended sediment concentrations on the ecophysiology of the porcelain crab Petrolisthes elongatus (Milne Edwards, 1837)

The porcelain crab Petrolisthes elongatus is a particulate suspension feeding species common to coastal areas of New Zealand (NZ). Consistent with the responses of other suspension feeding species, it is likely to be negatively influenced by elevated suspended sediment concentrations. Laboratory experiments were conducted to quantify the effect of temperature (12 °C, 15 °C and 18 °C) and suspended sediment concentration (total particulate matter (TPM): low < 100 mg L^− 1; medium 100-1000 mg L^− 1; high > 1000 mg L^− 1) on the clearance rate (CR in L h^− 1), oxygen uptake rate (VO₂ in mL h⁻¹), net absorption efficiency (AE), and net energy budget (NEB in J h^− 1) of P. elongatus across a range of sizes. Variation in CR and AE was independent of temperature and of body size, but were significantly different (P < 0.05) at low and medium suspended sediment concentrations compared with high suspended sediment concentrations. CR responded in a non-linear manner to changes in TPM, increasing with TPM up to a maximum value at medium-low concentrations (approximately 250 mg L^− 1) and then decreasing thereafter. CR had almost completely shut down at TPM concentrations of > 1000 mg L^− 1 and at particulate organic matter (POM) concentrations of > 250 mg L^− 1. AE was zero at approximate TPM and POM values of 1200 mg L^− 1 and 300 mg L^− 1, respectively. VO₂ was positively correlated with body size and with temperature, but was independent of TPM. NEB values for P. elongatus were low (approx 110 J g^− 1 h^− 1) at low sediment concentrations, were high (approx 320 J g^− 1 h^− 1) at medium sediment concentrations, and were negative (approx − 114 J g^− 1 h^− 1) at high sediment concentrations. These findings indicate that P. elongatus is likely to be food-limited at sediment concentrations of < 100 mg L^− 1, and severely negatively affected at sediment concentrations of > 1000 mg L^− 1, at least for the duration of such events which may persist for 2-3 days in coastal environments where this crab occurs.     

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.     

Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis

Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD₅) (from an inlet of 420 to 1000 mg L⁻¹) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L⁻¹), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha⁻¹ d⁻¹ and 529 kg BOD₅ ha⁻¹ d⁻¹ were achieved for a loading ranging from 242 to 1925 kg COD ha⁻¹ d⁻¹ and from 126 to 900 kg BOD₅ ha⁻¹ d⁻¹. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.     

In silico optimization and low structured kinetic model of poly[(R)-3-hydroxybutyrate] synthesis by Cupriavidus necator DSM 545 by fed-batch cultivation on glycerol

Glycerol was utilized by Cupriavidus necator DSM 545 for production of poly-3-hydroxybutyrate (PHB) in fed-batch fermentation. Maximal specific growth rates (0.12 and 0.3 h⁻¹) and maximal specific non-growth PHB production rate (0.16 g g⁻¹ h⁻¹) were determined from two experiments (inocula from exponential and stationary phase). Saturation constants for nitrogen (0.107 and 0.016 g L⁻¹), glycerol (0.05 g L⁻¹), non-growth related PHB synthesis (0.011 g L⁻¹) and nitrogen/PHB related inhibition constant (0.405 g L⁻¹), were estimated. Five relations for specific growth rate were tested using mathematical models. In silico performed optimization procedures (varied glycerol/nitrogen ratio and feeding) has resulted in a PHB content of 70.9%, shorter cultivation time (23 h) and better PHB yield (0.347 g g⁻¹). Initial concentration of biomass 16.8 g L⁻¹ and glycerol concentration in broth between 3 and 5 g L⁻¹ were decisive factors for increasing of productivity.     

Effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea

The effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea were examined in the laboratory. The irradiance at the light compensation point (I₀) was 14.40 μmol m^− 2 s^− 1 and the irradiance at growth saturation (I_s) was 114 μmol m^− 2 s^− 1. We exposed A. sanguinea to 48 combinations of temperature (5-30 °C) and salinity (5-40) under saturating irradiance; it exhibited its maximum growth rate of 1.13 divisions/day at a combination of 25 °C and salinity of 20. A. sanguinea was able to grow at temperatures from 10 to 30 °C and salinities from 10 to 40. This study revealed that A. sanguinea was a eurythermal and euryhaline organism; in Japan it should have formed blooms in early summer, when salinity was relatively low. In addition, it was noteworthy that A. sanguinea had markedly cold-durability, retaining the motile form of vegetative cells for more than 50 days at 5 °C and at salinities of 25-30.     

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).     

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).     

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.     

Particle reworking and solute transport by the sediment-living polychaetes Marenzelleria neglecta and Hediste diversicolor

This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind. m^− 2) and Hediste diversicolor (2 g ww, 800 ind. m^− 2) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient D_b and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient D_a. The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). D_b did not differ between the two species (2.4 × 10^− 3 cm² d^− 1) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y^− 1 for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min^− 1 for H. diversicolor and 0.003 mL min^− 1 for M. neglecta, corresponding to an area-specific rate of ca. 12 L m^− 2 d^− 1 at the used densities. D_a did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.     

Swimming in the sea hare Aplysia brasiliana: Cost of transport, parapodial morphometry, and swimming behavior

The energetics and behavior of the parapodial-swimming Aplysia brasiliana were investigated in order to compare net cost of transport (COT_net) between swimming and crawling, and to compare transport costs with other swimmers. Oxygen consumption (V_O2) increased with increasing animal mass for resting, crawling, and swimming animals. Slopes of the regressions of log V_O2 on log mass were 0.90, 0.91, and 0.89 for resting, crawling, and swimming, respectively. The regression for resting V_O2 on mass was significantly lower than regressions of crawling and swimming on mass, which fell into a statistically homogenous subgroup. During 4-h swimming bouts, parapodial beat frequency dropped by less than 10% of starting values after 2 h and then stabilized for the remainder of the trial, whereas velocity steadily decreased to about 70% of starting values over the 4-h period. Initial beat frequency (at the start of a swimming bout) was negatively related to body mass, varying from 1.1 beat s^− 1 for a 34 g individual to 0.7 beats s^− 1 for a 500 g individual. Final beat frequency (at the end of a swimming bout) was also negatively related to body mass, but had a significantly lower intercept than initial beat frequency. Neither initial swimming velocity nor final swimming velocity was related to mass, but final velocity was significantly lower than initial velocity. A 250 g A. brasiliana swam at 345 m h^− 1 and crawled at 7 m h^− 1. Swimming COT_net (0.1 ml O₂ kg^− 1 m^− 1) for a 250 g A. brasiliana was 50 times less than crawling COT_net (5.3 ml O₂ kg^− 1 m^− 1). While the crawling COT_net for A. brasiliana fell within the range of other marine gastropods, swimming COT_net was less than that of swimming crustaceans, and much less than another gastropod, Melibe leonina, that uses lateral bending to swim.     

Effects of temperature and salinity on the standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi

The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15-30 °C), salinity (0-45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O₂ mg wwt^− 1 h^− 1. The Q₁₀ value over the temperature range 15-25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O₂ mg wwt^− 1 h^− 1. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15-35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop.     

Selection of improved Beauveria bassiana (Bals.) Vuill. strains based on 2-deoxy-d-glucose resistance and physiological analysis

A series of 2-deoxy-d-glucose resistant mutants was obtained from wild type Beauveria bassiana 88 (Bb 88) by UV irradiation. Five mutants were characterized on Sabouraud Dextrose Agar and Chitin Agar for both radial extension rate (V_r) and specific growth rate (μ). These values were obtained after adjusting morphometric data to a mathematical model used for filamentous fungi. Additionally, the protease and lipase potency index, conidial size, viability, and production levels were analyzed. The highest values for those physiological measurements were obtained by mutant 882.5 which, relative to Bb 88, showed a 30% reduction in half-life (LT₅₀) on Sphenarium purpurascens, 70% on Acheta domesticus, and 71% on Tenebrio molitor larvae and adults. The half lethal concentration (LC₅₀) on T. molitor larvae was 2.8 × 10⁵ conidia/mL (con/mL) and 1.5 × 10⁶ con/mL, respectively, for mutant 882.5 and Bb 88. This demonstrates that mutant 882.5 is more virulent, with up to an 80% reduction in LC₅₀. This work provides a convenient method for improving strains to be used in biocontrol as a suitable alternative to transgenic constructs.     

Growth characteristics of Botryococcus braunii 765 under high CO2 concentration in photobioreactor

To understand the potential of cultivating Botryococcus braunii with flue gas (normally containing high CO₂) for biofuel production, growth characteristics of B. braunii 765 with 2-20% CO₂ aeration were investigated. The results showed that the strain could grow well without any obvious inhibition under all tested CO₂ concentrations with an aeration rate of 0.2 vvm, even without any culture pH adjustment (ranged from 6.0 to 8.0). The maximum biomass among all conditions was 2.31 g L⁻¹ on 25th day at 20% CO₂. Hydrocarbon content and algal colony size increased with the increase of CO₂ concentration. A negative correlation between algal biomass and culture total phosphorus was observed (from −0.828 to −0.911, P < 0.01). Additionally, 2% sodium hypochlorite solution was used for photobioreactor sterilization to cultivate B. braunii.     

Extraction and chemical characterization of starch from S. lycocarpum fruits

In this study the pulp from Solanum lycocarpum fruits was used as raw material for extraction of starch, resulting in a yield of 51%. The starch granules were heterogeneous in size, presenting a conical appearance, very similar to a high-amylose cassava starch. The elemental analysis (CHNS) revealed 64.33% carbon, 7.16% hydrogen and 0.80% nitrogen. FT-IR spectroscopy showed characteristic peaks of polysaccharides and NMR analysis confirmed the presence of the α-anomer of d-glucose. The S. lycocarpum starch was characterized by high value of intrinsic viscosity (3515 mPa s) and estimated molecular weight around 645.69 kDa. Furthermore, this starch was classified as a B-type and high amylose content starch, presenting 34.66% of amylose and 38% crystallinity. Endothermic transition temperatures (T_o = 61.25 °C, T_p = 64.5 °C, T_c = 67.5 °C), gelatinization temperature (ΔT = 6.3 °C) ranges and enthalpy changes (ΔH = 13.21 J g⁻¹) were accessed by DCS analysis. These results make the S. lycocarpum fruit a very promising source of starch for biotechnological applications.     

Decolorization of malachite green by cytochrome c in the mitochondria of the fungus Cunninghamella elegans

We studied the decolorization of malachite green (MG) by the fungus Cunninghamella elegans. The mitochondrial activity for MG reduction was increased with a simultaneous increase of a 9-kDa protein, called CeCyt. The presence of cytochrome c in CeCyt protein was determined by optical absorbance spectroscopy with an extinction coefficient (E_550-535) of 19.7 ± 6.3 mM⁻¹ cm⁻¹ and reduction potential of + 261 mV. When purified CeCyt was added into the mitochondria, the specific activity of CeCyt reached 440 ± 122 μmol min⁻¹ mg⁻¹ protein. The inhibition of MG reduction by stigmatellin, but not by antimycin A, indicated a possible linkage of CeCyt activity to the Qo site of the bc1 complex. The RT-PCR results showed tight regulation of the cecyt gene expression by reactive oxygen species. We suggest that CeCyt acts as a protein reductant for MG under oxidative stress in a stationary or secondary growth stage of this fungus.     

Biodegradation of phenanthrene and pyrene by Ganoderma lucidum

Biodegradation of two polycyclic aromatic hydrocarbons (PAHs), phenanthrene and pyrene, by a white rot fungus, Ganoderma lucidum, in broth cultures was investigated. It was found that the biomass of the organism decreased with the increase of PAH concentration in the cultures. In the cultures with 2 to 50 mg l⁻¹ PAHs, the degradation rate constants (k₁) increased with the PAH concentration, whereas, at the level of 100 mg l⁻¹, the degradation rate constants decreased. In the presence of 20 mg l⁻¹ PAHs, the highest degradation rates of both PAHs occurred in cultures with an initial pH of 4.0 at 30 °C. The addition of CuSO₄, citric acid, gallic acid, tartaric acid, veratryl alcohol, guaiacol, 2,2′-azino-bis-(3- ethylbenzothazoline-6-sulfonate) (ABTS) enhanced the degradation of both PAHs and laccase activities; whereas the supplement of oxalate, di-n-butyl phthalate (DBP), and nonylphenol (NP) decreased the degradation of both PAHs and inhibited laccase production. In conclusion, G. lucidum is a promising white rot fungus to degrade PAHs such as phenanthrene and pyrene in the environment.     

Simultaneous study of particle reworking, irrigation transport and reaction rates in sediment bioturbated by the polychaetes Heteromastus and Marenzelleria

The present study employed simultaneously methods to investigate particle and solute transport and reaction rates in sandy sediments inhabited by two worms (2500 m^− 2) with different feeding modes. Heteromastus filiformis is a head-down deposit-feeder and the main activities exerted by this worm are transport of particles as faecal pellets from subsurface to surface sediments and burrow ventilation. Marenzelleria viridis is a surface deposit-feeder that actively searches for food by burrowing near the sediment surface, producing a network of ventilated galleries in this zone. M. viridis exhibited 1.5 to 2.2 times higher particle mixing rates (D_b = 3.3 to 4 × 10^− 3 cm^− 2 d^− 1) compared to H. filiformis. In M. viridis treatments, continuous advection (eddy diffusion) was the major factor influencing solute transport resulting in apparent diffusion rates (D_a = 2.2 cm^− 2 d^− 1), which were 3 times higher than molecular diffusion within the sediment. In H. filiformis inhabited sediments, the transport of solutes was discontinuous and driven by a surprisingly high nonlocal exchange (α = 1.1-1.3 d^− 1), emphasizing its strong irrigation effects. Accordingly, the enhancement of solute fluxes was more pronounced for H. filiformis compared to M. viridis. Depth integrated TCO₂ production derived from diagenetic modelling, which takes into account three reaction zones, is in good agreement with rates obtained from measured fluxes, indicating the applicability of both approaches to get reliable rates. However, the reaction rates showed that the presence of animals had a modest effect on microbial carbon oxidation. The results proved that transport conditions are deeply related to feeding modes. Exchange of solutes was the most important transport process by H. filiformis, while M. viridis affected both mixing and solute transport.     

pH-control modes in a 5-L stirred-tank bioreactor for cell biomass and exopolysaccharide production by Tremella fuciformis spore

The effect of pH-control modes on cell growth and exopolysaccharide production by Tremella fuciformis was evaluated in a 5-L bioreactor. The results show that the maximal dry cell weight (DCW) and exopolysaccharide production were 23.57 and 4.48 g L⁻¹ in pH-stat fermentation, where the maximal specific growth rate (μ_max) and specific production rate of exopolysaccharide (P_P/X) were 1.03 and 0.24 d⁻¹, respectively; under pH-shift cultivation, the maximal DCW and exopolysaccharide production were 30.57 and 3.90 g L⁻¹, where the μ_max and P_P/X were 1.21 and 0.06 d⁻¹. Unlike batch fermentation, maximal DCW and exopolysaccharide production merely reached 15.04 and 2.0 g L⁻¹, where the μ_max and P_P/X were 0.86 and 0.05 d⁻¹, respectively. These results suggest that a pH-stat strategy is a more efficient way of performing the fermentation process to increase exopolysaccharide production. Furthermore, this research has also proved that the three-stage pH-control mode is effective for cell growth.     

Mono, di and polynuclear Cu(II)-azido complexes incorporating N,N,N reduced schiff base: syntheses, structure and magnetic behavior

Three kinds of copper(II) azide complexes have been synthesised in excellent yields by reacting Cu(ClO₄)₂ · 6H₂O with N,N-bis(2-pyridylmethyl)amine (L¹); N-(2-pyridylmethyl)-N′,N′-dimethylethylenediamine (L²); and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (L³), respectively, in the presence of slight excess of sodium azide. They are the monomeric Cu(L¹)(N₃)(ClO₄) (1), the end-to-end diazido-bridged Cu₂(L²)₂(μ-1,3-N₃)₂(ClO₄)₂ (2) and the single azido-bridged (μ-1,3-) 1D chain [Cu(L³)(μ-1,3-N₃)]_n(ClO₄)_n (3). The crystal and molecular structures of these complexes have been solved. The variable temperature magnetic moments of type 2 and type 3 complexes were studied. Temperature dependent susceptibility for 2 was fitted using the Bleaney-Bowers expression which led to the parameters J = −3.43 cm⁻¹ and R = 1 × 10⁻⁵. The magnetic data for 3 were fitted to Baker’s expression for S = 1/2 and the parameters obtained were J = 1.6 cm⁻¹ and R = 3.2 × 10⁻⁴. Crystal data are as follows. Cu(L¹)(N₃)(ClO₄): Chemical formula, C₁₂H₁₃ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 8.788(12), b = 13.045(15), c = 14.213(15) Å; β = 102.960(10)°; Z = 4. Cu(L²)(μ-N₃)(ClO₄): Chemical formula, C₁₀H₁₇ClN₆O₄Cu: crystal system, monoclinic; space group, P2₁/c; a = 10.790(12), b = 8.568(9), c = 16.651(17) Å; β = 102.360(10)°; Z = 4. [Cu(L³)(μ-N₃)](ClO₄): Chemical formula, C₁₂H₂₁ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 12.331(14), b = 7.804(9), c = 18.64(2) Å; β = 103.405(10)°; Z = 4.