Impact of hypoxia conditions on the Mnemiopsis leidyi A. Agassiz, 1865 bioluminescence

The findings of the study on the impact of hypoxia on the glow of the Black Sea ctenophore Mnemiopsis leidyi A. Agassiz, 1865 of three size groups (20–30, 30–45, and 45–60 mm) were obtained under experimental conditions. Peculiarities of ctenophore bioluminescence were studied during mechanical and chemical stimulation under the conditions of normoxia (at an oxygen concentration of 5.6–6.7 mg O₂ L⁻¹), moderate hypoxia (2.5–2.8 mg O₂ L⁻¹), and acute hypoxia (1.2–1.5 mg O₂ L⁻¹). An increase in the amplitude and energy of luminescence of the ctenophores mechanically and chemically stimulated was observed at an oxygen concentration of 1.2–1.5 mg O₂ L⁻¹ (acute hypoxia) in two size groups in the lobate form (30–45 and 45–60 mm). The inhibition of amplitude, energy, and duration of the signal was registered in M. leidyi ctenophores at the transitional stage from larva to the lobate form under conditions of acute hypoxia. It was noted that in normoxia, the values of the amplitude and energy of the bioluminescent signal of M. leidyi increase along with a size growth of an individual. This phenomenon was observed both during mechanical and chemical stimulations. Under conditions of acute hypoxia, this trend was mainly preserved. The universality of the relation between the bioluminescence of the organisms and their bioenergetics is obvious. The bioluminescent system of ctenophores has the role of an antioxidant system and is engaged in the neutralization of reactive oxygen species (ROS), that is the process during which photons are emitted. The response of the bioluminescent system to a decrease in oxygen concentration can be associated with an increase in the production of ROS that provides high values of the ctenophore luminescence under hypoxic conditions.     

Bioluminescent eddies of the World Ocean

Mesoscale eddies of the ocean (with a characteristic diameter of about 100 km and a life time-span of about several weeks) are habitats of plankton organisms, many of which are bioluminescent. The spatial heterogeneity of bioluminescence of the upper mixed layer associated with the impact of mesoscale eddies is poorly studied. The 45-year historical data set was retrieved, in order to select the bathy-photometric surveys carried out in the form of station grids and transects across eddies. Data from 71 expeditions deployed in 1966–2022 to the Atlantic Ocean, Indian Ocean and Mediterranean Sea basin were analyzed, in order for the spatial heterogeneity of bioluminescent fields to be elucidated across eddy fields. The stimulated bioluminescence intensity was characterized by the bioluminescent potential, which represented the maximal amount of radiant energy emitted in a given volume of water by bioluminescent organisms. The normalized bioluminescent potential over oceanographic station grids exhibited correlation with the eddy kinetic energy and zooplankton biomass (r = 0.8, at P = 0.001 and r = 0.7, at P = 0.05, respectively), in a broad range of energy and bioluminescence units (0.02–0.2 m² s⁻²; 0.4–92.0 × 10⁻⁸ W cm⁻² L⁻¹, respectively). Overall, estimates of bioluminescent potential variability on the mesoscale contribute to the assessment of the multiple-scale variation of the bioluminescent field of the World Ocean.     

Determination of pioglitazone hydrochloride by flow injection chemiluminescence tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex system

A novel flow injection-chemiluminescence (FI–CL) approach is proposed for the assay of pioglitazone hydrochloride (PG-HCl) based on its enhancing influence on the tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex (Ru(bipy)₃²⁺-DPA) CL system in sulfuric acid medium. The possible CL reaction mechanism is discussed with CL and ultraviolet (UV) spectra. The optimum experimental conditions were found as: Ru(bipy)₃²⁺, 5.0 × 10⁻⁵ M; sulfuric acid, 1.0 × 10⁻³ M; diperiodatoargentate(III) (DPA), 1.0 × 10⁻⁴ M; potassium hydroxide, 1.0 × 10⁻³ M; flow rate 4.0 ml min⁻¹ for each flow stream and sample loop volume, 180 μl. The CL intensity of PG-HCl was linear in the range of 1.0 × 10⁻³ to 5.0 mg L⁻¹ (R² = 0.9998, n = 10) with limit of detection [LOD, signal-to-noise ratio (S/N) = 3] of 2.2 × 10⁻⁴ mg L⁻¹, limit of quantification (LOQ, S/N = 10) of 6.7 × 10⁻⁴ mg L⁻¹, relative standard deviation (RSD) of 1.0 to 3.3% and sampling rate of 106 h⁻¹. The methodology was satisfactorily used to quantify PG-HCl in pharmaceutical tablets with recoveries ranging from 93.17 to 102.77 and RSD from 1.9 to 2.8%.     

Smoke-saturated Water and Karrikinolide Modulate Germination,Growth, Photosynthesis and Nutritional Values of Carrot (Daucus carota L.)

Plant-derived smoke is a positive regulator of seed germination and growth with regard to many plant species. Of the several compounds present in plant-derived smoke, karrikinolide or KAR₁ (3-methyl-2H-furo[2,3-c]pyran-2-one) is considered to be the major active growth-promoting compound. To test the efficacy of smoke-saturated water (SSW) and KAR₁ on carrot (Daucus carota L.), two separate pot experiments were simultaneously conducted in the same environmental conditions. SSW and KAR₁ treatments were applied to the plants in the form of aqueous solutions of variable concentrations. Prior to sowing, seeds were soaked in the solutions of SSW (25.8 µg L⁻¹_, 51.6 µg L⁻¹,103.2 µg L⁻¹ and 258.0 µg L⁻¹) and KAR₁ (0.015 µg L⁻¹, 0.150 µg L⁻¹, 1.501 µg L⁻¹ and 15.013 µg L⁻¹). Percent seed germination, vegetative growth, photosynthesis and nutritional values were the major parameters through which the plant response to the applied treatments was investigated. The results obtained indicated a significant improvement in all the plant attributes studied. In general, SSW (51.6 µg L⁻¹) and KAR₁ (1.501 µg L⁻¹) proved optimum treatments for most the parameters. As compared to the control, 51.6 µg L⁻¹ of SSW and 1.501 µg L⁻¹ of KAR₁ increased the percent seed germination by 58.0% and 54.4%, respectively. Over the control, the values of plant height and net photosynthetic rate were enhanced by 33.9% and 40.9%, respectively, due to 51.6 µg L⁻¹ of SSW, while the values of these parameters were increased by 25.2% and 34.0%, respectively, due to 1.501 µg L⁻¹ of KAR₁. In comparison with the control, treatment 51.6 µg L⁻¹ of SSW increased the contents of β-carotene and ascorbic acid by 32.7% and 37.9%, respectively, while the treatment 1.501 µg L⁻¹ M of KAR₁ enhanced these contents by 42.0% and 48.4%, respectively. This study provides an insight into an affordable and feasible method of crop improvement.

     

Influence of linear alkylbenzene sulfonate and ethanol on the degradation kinetics of domestic sewage in co-digestion with commercial laundry wastewater

The influence of ethanol on the degradation kinetics of linear alkyl benzene sulfonate (LAS) and organic matter was investigated using batch experiments with different initial LAS concentrations (8.3 mg L⁻¹ to 66.9 mg L⁻¹) and biomass immobilized on sand. Data were fitted with a substrate inhibition model. Concentrations of 2.4 mg LAS L⁻¹ and 18.9 mg LAS L⁻¹ (without and with ethanol) provided the maximum LAS utilization rate by the biomass (S_bm). For LAS degradation, ethanol addition favored a lower decrease in the specific substrate utilization rate (r_obs), even at the LAS concentration usually reported as inhibitory (> 14.4 mg L⁻¹). For organic matter degradation, r_obs was higher with ethanol. Higher biomass differentiation was observed at higher LAS concentrations. With ethanol, microbial selection occurred at LAS concentrations near S_bm. At higher LAS concentrations, the dominance and diversity values did not change significantly with ethanol, whereas without ethanol, their behaviors were irregular.

     

Effective biodegradation of 2,4,6-trinitrotoluene using a novel bacterial strain isolated from TNT-contaminated soil

In this environmental-sample based study, rapid microbial-mediated degradation of 2,4,6-trinitrotoluene (TNT) contaminated soils is demonstrated by a novel strain, Achromobacter spanius STE 11. Complete removal of 100 mg L⁻¹ TNT is achieved within only 20 h under aerobic conditions by the isolate. In this bio-conversion process, TNT is transformed to 2,4-dinitrotoluene (7 mg L⁻¹), 2,6-dinitrotoluene (3 mg L⁻¹), 4-aminodinitrotoluene (49 mg L⁻¹) and 2-aminodinitrotoluene (16 mg L⁻¹) as the key metabolites. A. spanius STE 11 has the ability to denitrate TNT in aerobic conditions as suggested by the dinitrotoluene and NO₃ productions during the growth period. Elemental analysis results indicate that 24.77 mg L⁻¹ nitrogen from TNT was accumulated in the cell biomass, showing that STE 11 can use TNT as its sole nitrogen source. TNT degradation was observed between pH 4.0–8.0 and 4–43 °C; however, the most efficient degradation was at pH 6.0–7.0 and 30 °C.     

MRP2 and the Transport Kinetics of Cysteine Conjugates of Inorganic Mercury

Human exposure to mercuric species occurs regularly throughout the world. Mercuric ions may accumulate in target cells and subsequently lead to cellular intoxication and death. Therefore, it is important to have a thorough understanding of how transportable species of mercury are handled by specific membrane transporters. The purpose of the current study was to characterize the transport kinetics of cysteine (Cys)-S-conjugates of inorganic mercury (Cys-S-Hg-S-Cys) at the site of the multidrug resistance-associated transporter 2 (MRP2). In order to estimate the maximum velocity (V _max) and Michaelis constant (K _m) for the uptake of Cys-S-Hg-S-Cys mediated by MRP2, in vitro studies were carried out using radioactive Cys-S-Hg-S-Cys (5 μM) and inside-out membrane vesicles made from Sf9 cells transfected with MRP2. The V _max was estimated to be 74.3 ± 10.1 nmol mg protein⁻¹ 30 s⁻¹ while the K _m was calculated to be 63.4 ± 27.3 μM. In addition, in vivo studies were utilized to measure the disposition of inorganic mercury (administered dose 0.5 μmol kg⁻¹ in 2 mL normal saline) over time in Wistar and TR¯ (Mrp2-deficient) rats. These studies measured the disposition of mercuric ions in the kidney, liver, and blood. In general, the data suggest that the initial uptake of mercuric conjugates into select target cells is rapid followed by a period of slower uptake and accumulation. Overall, the data indicate that MRP2 transports Cys-S-Hg-S-Cys in a manner that is similar to that of other MRP2 substrates.

     

Effects of Temperature and Body Size on the Swimming Speed of Larval and Juvenile Atlantic Cod (Gadus Morhua): Implications for Individual-based Modelling

Synopsis The routine swimming speed (S) of three groups of 4, 9 and 32 cm total length (L_T) juvenile cod (Gadus morhua) was quantified in the laboratory at 6 – 10 different temperatures (T) between 3.2 and 16.7°C. At temperatures between 5 and 15°C, mean group S increased exponentially with increasing T (S=a e^bT) and the effect of temperature (b = 0.082, Q₁₀ = 2.27) was not significantly different among the groups (over the 8-fold difference in fish sizes of early- and post-settlement juveniles). Differences in mean S among individuals within each group were quite large (coefficient of variation = 40 – 80%). Swimming data for juveniles and those collected for groups of 0.4, 0.7 and 0.9 cm standard length (L_S) larvae were combined to assess the effect of body size on S. At 8°C, S (mm s⁻¹) increased with L_S (mm) according to: S = 0.26L_S^Φ−5.28L_S⁻¹, where Φ = 1.55L_S^−0.08. Relative S (body lengths s⁻¹) was related to L_S by a dome-shaped relationship having a maximum value (0.49 body lengths s⁻¹) at 18.5 – 19 mm L_S corresponding to the sizes of fish at the end of larval-juvenile metamorphosis. Previous larval cod IBM’s using a cruise-predator mode likely overestimated rates of foraging (prey searching and encounters) by a factor of ~2, whereas foraging rates in pause-travel models are closer to estimates of swimming velocities obtained in this and other laboratory studies.     

Outdoor open thin-layer microalgal photobioreactor: potential productivity

We have previously estimated the productivity and photosynthetic efficiency of the microalga Chlorella sp. grown in an outdoor open thin-layer photobioreactor under climate conditions typical of the Middle European region, i.e. with many days unsuitable for intensive growth of algae (cloudy and rainy days, low air temperature, low solar PAR input).To estimate the real potential productivity of the bioreactor, we collected data on algae yields obtained during clear summer day periods. Cultivation was performed in fed-batch cycles in a bioreactor with a 224 m² culture area (length 28 m, slope 1.7%), and a 6–7 mm-thick layer of algal culture. The suspension volume in the bioreactor was 2,000 L. The mean values found for Třeboň (49°N), Czech Republic, as an average of several sunny summer cultivation periods in July, were: net areal productivity, P _net = 38.2 g dry weight (DW) m^-2 day^-1; net volumetric productivity, P_vol, = 4.3 g algal DW L^-1 day^-1, photosynthetic efficiency (based on PAR), η_net = 7.05%. The peak values were: P _net about 50 g (DW) m^-2 day^-1, η_net about 9%. Algal growth rate was practically linear up to high biomass densities (40–50 g DW L^-1, corresponding to an areal density of 240–300 g DW m^-2), at which point the culture was harvested. The concentration of dissolved oxygen increased from about 10 mg L^-1 at the beginning to about 23 mg L^-1 at the end of culture area at noon. Use of the above-described technology for economical production of bioethanol is proposed.     

Disruption of glpF gene encoding the glycerol facilitator improves 1,3-propanediol production from glucose via glycerol in Escherichia coli

Engineered Escherichia coli has recently been applied to produce 1,3-propanediol (1,3-PDO) from glucose. A metabolic intermediate in the production pathway, glycerol, is partially secreted into the extracellular of E. coli through a glycerol facilitator encoded by glpF, and this secretion consequently decreases 1,3-PDO production. Therefore, we aimed to determine whether disrupting the glpF gene would improve 1,3-PDO production in E. coli. The intracellular glycerol concentration in a glpF-disruptant was 7·5 times higher than in a non-disruptant. The glpF-disrupted and non-disrupted E. coli strains produced 0·26 and 0·09 g l⁻¹ of 1,3-PDO, respectively, from 1% glucose after 72 h of cultivation. The specific growth rate (μ) and the 1,3-PDO yield from glucose (Y_P/S) in the disruptant were higher than those in the non-disruptant (ΔglpF, μ = 0·08 ± 0·00 h⁻¹, Y_P/S = 0·06 mol mol-glucose⁻¹; BW25113, μ = 0·06 ± 0·00 h⁻¹, Y_P/S = 0·02 mol mol-glucose⁻¹). Disruption of the glpF gene decreased the production of the by-product, acetic acid. These results indicated that disruption of glpF increased the intracellular concentration of glycerol and consequently increased 1,3-PDO production in E. coli.     

Molecular cloning,expression, and biochemical characterization of a novel cold-active α-amylase from Bacillus sp. dsh19-1

A novel gene (ANK58566) encoding a cold-active α-amylase was cloned from marine bacterium Bacillus sp. dsh19-1 (CCTCC AB 2015426), and the protein was expressed in Escherichia coli. The gene had a length of 1302 bp and encoded an α-amylase of 433 amino acids with an estimated molecular mass of 50.1 kDa. The recombinant α-amylase (AmyD-1) showed maximum activity at 20 °C and pH 6.0, and retained about 35.7% of activity at 4 °C. The AmyD-1 activity was stimulated by Ca²⁺ and Na⁺. However, the chelating agent, EDTA, inactivated the enzyme. Moreover, AmyD-1 displayed extreme salt tolerance, with the highest activity in the presence of 2.0 M NaCl and 60.5% of activity in 5.0 M NaCl. The K_m, V_max and k_cat of AmyD-1 in 2.0 M NaCl were 2.8 mg ml⁻¹, 21.8 mg ml⁻¹ min⁻¹ and 933.5 s⁻¹, respectively, at 20 °C and pH 6.0 with soluble starch as substrate. MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry) revealed that the end products of starch hydrolysis by AmyD-1 were glucose, maltose, maltotriose, maltotetraose, and malt oligosaccharides. Thus, AmyD-1 is one of the very few α-amylases that can tolerate low temperatures and high salt concentrations, which makes it to be a potential candidate for research in basic and applied microbiology.

     

Characteristics and molecular determinants of a highly selective and efficient glycyrrhizin-hydrolyzing β-glucuronidase from Staphylococcus pasteuri 3I10

Glycyrrhizin (GL), the principal sweet-tasting bioactive ingredient of licorice (root of Glycyrrhiza glabra), shows poor oral absorption and gut microbial transformation of GL to glycyrrhetinic acid (GA) plays a major role for its multiple pharmacological effects. Co-administration of GL-hydrolyzing bacteria appears to be a feasible strategy to enhance GA exposure. This study reported a gut bacterial strain Staphylococcus pasteuri 3I10 which exhibited moderate p-nitrophenyl-β-D-glucuronide (PNPG)-hydrolyzing activity but low GL deglucuronidation activity in its crude lysate. The gus gene encoding S. pasteuri 3I10 β-glucuronidase was successfully cloned and overexpressed in Escherichia coli BL21(DE3). The purified β-glucuronidase (SpasGUS) was 71 kDa and showed optimal pH and temperature at 6.0 and 50 °C, respectively. Comparing to E. coli β-glucuronidase (EcoGUS), SpasGUS displayed lower velocity and affinity to PNPG hydrolysis (V_max 16.1 ± 0.9 vs 140.0 ± 4.1 μmolmin⁻¹ mg⁻¹; K_m 469.4 ± 73.4 vs 268.0 ± 25.8 μM), but could selectively convert GL to GA at much higher efficiency (V_max 0.41 ± 0.011 vs 0.005 ± 0.002 μmolmin⁻¹ mg⁻¹; K_m 116.9 ± 15.4 vs 53.4 ± 34.8 μM). Molecular docking studies suggested SpasGUS formed hydrogen bond interactions with the glucuronic acids at Asn414, Glu415 and Leu450, and Val159, Tyr475, Ala368, and Phe367 provided a hydrophobic environment for enhanced activity. Two special substrate interaction loops near the binding pocket of SpasGUS (loop 1 β-glucuronidase) may account for the selective and efficient bioconversion of GL to GA, predicting that loop 1 β-glucuronidases show high possibility in processing GL than mini-loop 1 and loop 2 β-glucuronidases. These findings support potential applications of SpasGUS in cleaving GL to facilitate GA production in vivo or in pharmaceutical industry.

     

Effects of temperature on metabolic rate and lower dissolved oxygen tolerance of juvenile speckled peacock bass Cichla temensis

The speckled peacock bass Cichla temensis is a popular sport and food fish that generates substantial angling tourism and utilitarian harvest within its range. Its popularity and value make this species important for management and a potential aquaculture candidate for both fisheries enhancement and food fish production. However, little is known of optimal physiochemical conditions in natural habitats, which also are important for the development of hatchery protocols for handling, spawning and grow-out. Speckled peacock bass have been documented to have high sensitivity to extreme temperatures, but the metabolic underpinnings have not been evaluated. In this study, the effects of temperature (25, 30 and 35°C) on the standard metabolic rate (SMR) and lower dissolved oxygen tolerance (LDOT) of juvenile speckled peacock bass (mean ± standard error total length 153 ± 2 mm and wet weight 39.09 ± 1.37 g) were evaluated using intermittent respirometers after an acclimation period of 2 weeks. Speckled peacock bass had the highest SMR at 35°C (345.56 ± 19.89 mgO₂ kg⁻¹ h⁻¹), followed by 30°C (208.16 ± 12.45 mgO₂ kg⁻¹ h⁻¹) and 25°C (144.09 ± 10.43 mgO₂ kg⁻¹ h⁻¹). Correspondingly, the Q₁₀, or rate of increase in aerobic metabolic rate (MO₂) relative to 10°C, for 30–35°C was also greater (2.76) than from 25 to 30°C (2.08). Similarly, speckled peacock bass were the most sensitive to hypoxia at the warmest temperature, with an LDOT at pO₂ of 90 mmHg (4.13 mg l⁻¹) at 35°C compared to pO₂ values of 45 mmHg (2.22 mg l⁻¹) and 30 mmHg (1.61 mg l⁻¹) at 30 and 25°C, respectively. These results indicate that speckled peacock bass are sensitive to temperatures near 35°C, therefore we recommend managing and rearing this species at 25–30°C.     

Enhanced CO2 biofixation and protein production by microalgae biofilm attached on modified surface of nickel foam

In this work, a photobioreactor with microalgae biofilm was proposed to enhance CO₂ biofixation and protein production using nickel foam with the modified surface as the carrier for immobilizing microalgae cells. The results demonstrated that, compared with microalgae suspension, microalgae biofilm lowered mass transfer resistance and promoted mass transfer efficiency of CO₂ from the bubbles into the immobilized microalgae cells, enhancing CO₂ biofixation and protein production. Moreover, parametric studies on the performance of the photobioreactor with microalgae biofilm were also conducted. The results showed that the photobioreactor with microalgae biofilm yielded a good performance with the CO₂ biofixation rate of 4465.6 µmol m⁻³ s⁻¹, the protein concentration of effluent liquid of 0.892 g L⁻¹, and the protein synthesis rate of 43.11 g m⁻³ h⁻¹. This work will be conducive to the optimization design of microalgae culture system for improving the performance of the photobioreactor.

     

A simple cryopreservation protocol of <Emphasis Type="Italic">Dioscorea bulbifera</Emphasis> L. embryogenic calli by encapsulation-vitrification

Embryogenic calli of Dioscorea bulbifera L. were successfully cryopreserved using an encapsulation-vitrification method. Embryogenic calli were cooled at 6°C for 5 days on solid MS medium (Murashige and Skoog 1962) containing 2 mg L⁻¹ Kinetin (Kn), 0.5 mg L⁻¹ α-naphthalene acetic acid (NAA) and 0.5 mg L⁻¹ 2,4-dichlorophenoxy-acetic acid (2,4-D). These were prior precultured on liquid basal MS medium enriched with 0.75 M sucrose at 25 ± 1°C for 7 days. Embryogenic calli were osmoprotected with a mixture of 2 M glycerol and 1 M sucrose for 80 min at 25°C and dropped in a 0.1 M CaCl₂ solution containing 0.4 M sucrose at 25 ± 1°C. After 15 min of polymerization, Ca-alginate beads (about 4 mm in diameter) were dehydrated for 150 min at 0°C in a PVS₂ solution [30% glycerol, 15% ethylene glycol, and 15% dimethyl sulfoxide (w/v)] containing 0.5 M sucrose. The encapsulated embryogenic calli were then plunged directly into LN (liquid nitrogen) for 1 h. After rapid thawing in a water bath (37°C; 2 min), the beads were washed 3 times at 10-min intervals in liquid basal MS medium containing 1.2 M sucrose. Following thawing, the embryogenic calli were transferred to fresh solid basal MS media supplemented with Kn 2 mg L⁻¹, 0.09 M sucrose and 0.75% (w/v) agar (embryoid induction medium) and cultured under light conditions of 12-h photoperiod with a light intensity of 36 μmol m⁻² s⁻¹ provided by white cool fluorescent tubes after a 2-day dark period at 25 ± 1°C. After 30 days, the embryoids developed from embryogenic calli were transferred to fresh solid basal MS media supplemented with Kn 2 mg L⁻¹, NAA 0.5 mg L⁻¹, 3% (w/v) sucrose and 0.75% (w/v) agar (regeneration medium). After 60 days, the embryogenic calli developed normal shoots and roots. No morphological abnormalities were observed after plating on the regeneration medium. The survival rate of encapsulated vitrified embryogenic callus reached over 70%. This encapsulation-vitrification method appears promising as a routine and simple method for the cryopreservation of Dioscorea bulbifera embryogenic callus.     

Comparative physiology of Australian quolls (Dasyurus; Marsupialia)

Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that standard physiological variables of these quolls are consistent with allometric expectations for marsupials. Nevertheless, inter-specific patterns amongst the quolls are consistent with their different environments. The lower T _b of northern quolls (34°C) may provide scope for adaptive hyperthermia in the tropics, and they use torpor for energy/water conservation, whereas the larger mesic species (eastern and tiger quolls) do not appear to. Thermolability varied from little in eastern (0.035°C °C⁻¹) and tiger quolls (0.051°C oC⁻¹) to substantial in northern quolls (0.100°C oC⁻¹) and chuditch (0.146°C oC⁻¹), reflecting body mass and environment. Basal metabolic rate was higher for eastern quolls (0.662 ± 0.033 ml O₂ g⁻¹ h⁻¹), presumably reflecting their naturally cool environment. Respiratory ventilation closely matched metabolic demand, except at high ambient temperatures where quolls hyperventilated to facilitate evaporative heat loss; tiger and eastern quolls also salivated. A higher evaporative water loss for eastern quolls (1.43 ± 0.212 mg H₂O g⁻¹ h⁻¹) presumably reflects their more mesic distribution. The point of relative water economy was low for tiger (−1.3°C), eastern (−12.5°C) and northern (+3.3) quolls, and highest for the chuditch (+22.6°C). We suggest that these differences in water economy reflect lower expired air temperatures and hence lower respiratory evaporative water loss for the arid-zone chuditch relative to tropical and mesic quolls.     

Effects of heavy metals on aerobic denitrification by strain Pseudomonas stutzeri PCN-1

Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67∼6.67 mg L⁻¹ h⁻¹), higher nitrite accumulation (47.3∼99.8 mg L⁻¹), and higher N₂O emission ratios (5∼283 mg L⁻¹/mg L⁻¹). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0∼0.05 mg L⁻¹) was found, and the absence of Cu resulted in massive N₂O emission due to poor synthesis of N₂O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5∼2.5 mg L⁻¹) > Cu(II) (0.5∼5 mg L⁻¹) > Ni(II) (2∼10 mg L⁻¹) > Zn(II) (25∼50 mg L⁻¹). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ≈ cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.

     

Mathematical modeling of the ethanol fermentation of cashew apple juice by a flocculent yeast: the effect of initial substrate concentration and temperature

In this work, the effect of initial sugar concentration and temperature on the production of ethanol by Saccharomyces cerevisiae CCA008, a flocculent yeast, using cashew apple juice in a 1L-bioreactor was studied. The experimental results were used to develop a kinetic model relating biomass, ethanol production and total reducing sugar consumption. Monod, Andrews, Levenspiel and Ghose and Tyagi models were investigated to represent the specific growth rate without inhibition, with inhibition by substrate and with inhibition by product, respectively. Model validation was performed using a new set of experimental data obtained at 34 °C and using 100 g L⁻¹ of initial substrate concentration. The model proposed by Ghose and Tyagi was able to accurately describe the dynamics of ethanol production by S. cerevisiae CCA008 growing on cashew apple juice, containing an initial reducing sugar concentration ranging from 70 to 170 g L⁻¹ and temperature, from 26 to 42 °C. The model optimization was also accomplished based on the following parameters: percentage volume of ethanol per volume of solution (%V _ethanol/V _solution), efficiency and reaction productivity. The optimal operational conditions were determined using response surface graphs constructed with simulated data, reaching an efficiency and a productivity of 93.5% and 5.45 g L⁻¹ h⁻¹, respectively.

     

Length to weight ratio of four fish species in estuary areas in the Northeast region of Brazil

The length to weight ratio (LWR) was used to estimate populations of four fish species sampled on the Amazon coast of the state of Maranhão, Brazil. The fishes were sampled in 2018 and 2019 by artisanal coastal fishing, using gillnets (0.20–0.60 mm). The parameters a and b of the equation W_T = a L_T^b were estimated. The obtained LWRs were W_T = 0.06LT^2.93, (r²) = .989 for Oligoplites saliens; W_T = 0.061L_T^2.57, (r²) = .982 for Peprilus crenulatus; W_T = 0.014L_T^2.80, (r²) = .985 for Bagre bagre; and W_T = 0.035L_T^3.21, (r²) = .981 for Nebris microps.     

Effects of temperature and stocking density on intensive culture of Pacific white shrimp in freshwater

In aquaculture, the application of predictive techniques based on statistical-mathematical modeling allows not only to project and study individual growth trajectories, but also to evaluate the probable effect of external factors that would explain their behavior over time. This is the case of this work, which takes the above as a principle to demonstrate the effect of water temperature on the growth of the Pacific white shrimp Litopenaeus vannamei cultured in fresh water (0 mg L⁻¹), using densities of 90, 120, 180, 230, 280 and 330 shrimp m⁻². Shrimp were exposed to water temperature between 11.5 °C and 31.6 °C. Temperature effect was determined using a parameterized Gompertz growth model with experimental data from each initial culture density. The best shrimp productivity yield was obtained above 26 °C, and the least efficient was below 22 °C. Densities of 90–180 shrimp m⁻² and 230–330 shrimp m⁻² generated a maximum average size of 12.6 g and 8.8 g in 30 weeks, respectively. Here we present the implications of the effect of water temperature on the intensive culture of white shrimp with zero salinity (0 mg L⁻¹) using these techniques from a predictive analytical approach.