Structural and diffusion properties of formamide/water mixture interacting with TiO2 surface

The photoreaction and adsorption properties on surfaces, thermal decomposition, chemical transformation, and other properties of the formamide molecule are widely used to understand the origins of the formation of biological molecules (nucleosides, amino acids, DNA, monolayers, etc.) needed for life. The titanium oxide (TiO₂) surface can act both as a template on which the accumulation of adsorbed molecules like formamide occurs through the concentration effect, and as a catalytic material that lowers the activation energy needed for the formation of intermediate products. In this paper, a formamide–water solution interacting with TiO₂ (anatase) surface is simulated using the molecular dynamics method. The structural, diffusion and density properties of formamide–water mixture on TiO₂ are established for a wide temperature range from T = 250 K up to T = 400 K.     

Forming nanoparticles of α-amylase and embedding them into solid surfaces

In the current work nanoparticles (NPs) of α-amylase were generated in an aqueous solution using high-intensity ultrasound, and were subsequently immobilized on polyethylene (PE) films, or polycarbonate (PC) plates, or on microscope glass slides. The α-amylase NPs coated on the solid surfaces have been characterized by ESEM, TEM, FTIR, XPS and AFM. The substrates immobilized with α-amylase were used for hydrolyzing soluble potato starch to maltose. The amount of enzyme introduced in the substrates, leaching properties, and the catalytic activity of the immobilized enzyme were compared. The catalytic activity of the amylase deposited on the three solid surfaces was compared to that of the same amount of free enzyme at different pHs and temperatures. α-Amylase coated on PE showed the best catalytic activity in all the examined parameters when compared to native amylase, especially at high temperatures. When immobilized on glass, α-amylase showed better activity than the native enzyme over all pH and temperature values studied. However, the immobilization on PC did not improve the enzyme activity at any pH and any temperature compared to the free amylase. The kinetic parameters, K_m and V_max were also calculated. The amylase coated PE showed the most favorable kinetic parameters (K_m = 5 g L⁻¹ and V_max = 5E−07 mol mL⁻¹ min⁻¹). In contrast, the anchored enzyme-PC exhibited unfavorable kinetic parameters (K_m = 16 g L⁻¹, V_max = 4.2E−07 mol mL⁻¹ min⁻¹). The corresponding values for amylase-glass were K_m = 7 g L⁻¹, V_max = 1.8E−07 mol mL⁻¹ min⁻¹, relative to those obtained for the free enzyme (K_m = 6.6 g L⁻¹, V_max = 3.3E−07 mol mL⁻¹ min⁻¹).     

Effects of Zn2+ and niflumic acid on photosynthesis in Glycine soja and Glycine max seedlings under NaCl stress

The effects of two anion/Cl^? channel inhibitors, Zn²⁺ and niflumic acid (NA), on seedling photosynthetic and fluorescent parameters of two Glycine soja populations (salt-tolerant BB52; salt-sensitive N23227) and Glycine max cultivar (salt-tolerant Lee68) were studied and compared under salt stress. Treatments with Zn²⁺ and NA only (10, 20 μmol L^?1) were also imposed for comparisons. Results showed that, there were non-toxic and non-nutritional effects of Zn²⁺ and NA treatments alone on seed germination and seedling growth of soybeans. Under 150 mmol L^?1 NaCl for 6 d, leaf chlorophyll and carotenoid contents, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (Tr), and the maximum photochemical efficiency of photosystem II (PS II) (F_v/F_m) except the stomatal limitation (Ls) significantly decreased in three kinds of soybean seedlings when compared with their control plants. The NaCl stress plus additional 20 μmol L^?1 Zn showed an obvious enhancement of leaf chlorophyll and carotenoid contents, P_n, G_s, C_i and Tr, especially for the G. max cultivar Lee68, but the supplementation of 20 μmol L^?1 NA showed the reverse effects.     

Exceptional thermal tolerance and water resistance in the mite Paratarsotomus macropalpis (Erythracaridae) challenge prevailing explanations of physiological limits

Physiological performance and tolerance limits in metazoans have been widely studied and have informed our understanding of processes such as extreme heat and cold tolerance, and resistance to water loss. Because of scaling considerations, very small arthropods with extreme microclimatic niches provide promising extremophiles for testing predictive physiological models. Corollaries of small size include rapid heating and cooling (small thermal time constants) and high mass-specific metabolic and water exchange rates. This study examined thermal tolerance and water loss in the erythracarid mite Paratarsotomus macropalpis (Banks, 1916), a species that forages on the ground surface of the coastal sage scrub habitat of Southern California, USA. Unlike most surface-active diurnal arthropods, P. macropalpis remains active during the hottest parts of the day in midsummer. We measured water-loss gravimetrically and estimated the critical thermal maximum (CT_max) by exposing animals to a given temperature for 1 h and then increasing temperature sequentially. The standardized water flux of 4.4 ng h⁻¹ cm⁻² Pa⁻¹, averaged for temperatures between 22 and 40 °C, is among the lowest values reported in the literature. The CT_max of 59.4 °C is, to our knowledge, the highest metazoan value reported for chronic (1-h) exposure, and closely matches maximum field substrate temperatures during animal activity. The extraordinary physiological performance seen in P. macropalpis likely reflects extreme selection resulting from its small size and resultant high mass-specific water loss rate and low thermal time-constant. Nevertheless, the high water resistance attained with a very thin lipid barrier, and the mite’s exceptional thermal tolerance, challenge existing theories seeking to explain physiological limits.     

Enhanced activity of immobilized pepsin nanoparticles coated on solid substrates compared to free pepsin

In the present work nanoparticles (NPs) of pepsin were generated in an aqueous solution using high-intensity ultrasound, and were subsequently immobilized on low-density polyethylene (PE) films, or on polycarbonate (PC) plates, or on microscope glass slides. The pepsin NPs coated on the solid surfaces have been characterized by HRSEM, TEM, FTIR, XPS and DLS. The amount of enzyme introduced on the substrates, the leaching properties, and the catalytic activity of the immobilized enzyme on the three surfaces are compared. Catalytic activities of pepsin deposited onto the three solid surfaces as well as free pepsin, without sonication, and free pepsin NPs were compared at various pH levels and temperatures using a hemoglobin assay. Compared to native pepsin, pepsin coated onto PE showed the best catalytic activity in all the examined parameters. Pepsin immobilized on glass exhibited better activity than the native enzyme, especially at high temperatures. Enzyme activity of pepsin immobilized on PC was no better than native enzyme activity at all temperatures at pH 2, and only over a narrow pH range at 37 °C was the activity improved over the native enzyme. A remarkable observation is that immobilized pepsin on all the surfaces was still active to some extent even at pH 7, while free pepsin was completely inactive. The kinetic parameters, K_m and V_max were also calculated and compared for all the samples. Relative to the free enzyme, pepsin coated PE showed the greatest improvement in kinetic parameters (K_m = 15 g/L, V_max = 719 U/mg versus K_m = 12.6 g/L and V_max = 787 U/mg, respectively), whereas pepsin coated on PC exhibited the most unfavorable kinetic parameters (K_m = 18 g/L, V_max = 685 U/mg). The values for the anchored enzyme-glass were K_m = 19 g/L, V_max = 763 U/mg.     

Growth of the fungus Paecilomyces lilacinus with n-hexadecane in submerged and solid-state cultures and recovery of hydrophobin proteins

The filamentous fungus Paecilomyces lilacinus was grown on n-hexadecane in submerged (SmC) and solid-state (SSC) cultures. The maximum CO₂ production rate in SmC (V_max = 11.7 mg CO₂ L_g⁻¹ day⁻¹) was three times lower than in SSC (V_max = 40.4 mg CO₂ L_g⁻¹ day⁻¹). The P. lilacinus hydrophobin (PLHYD) yield from the SSC was 1.3 mg PLHYD g protein⁻¹, but in SmC, this protein was not detected. The PLHYD showed a critical micelle concentration of 0.45 mg mL⁻¹. In addition, the PLHYD modified the hydrophobicity of Teflon from 130.1 ± 2° to 47 ± 2°, forming porous structures with some filaments <1 μm and globular aggregates <0.25 μm diameter. The interfacial studies of this PLHYD could be the basis for the use of the protein to modify surfaces and to stabilize compounds in emulsions.     

The effects of light intensity on the growth of Japanese Gambierdiscus spp. (Dinophyceae)

Marine toxic dinoflagellates of the genus Gambierdiscus are the causative agents of ciguatera fish poisoning (CFP), a form of seafood poisoning that is widespread in tropical, subtropical and temperate regions worldwide. The distributions of Gambierdiscus australes, Gambierdiscus scabrosus and two phylotypes of Gambierdiscus spp. type 2 and type 3 have been reported for the waters surrounding the main island of Japan. To explore the bloom dynamics and the vertical distribution of these Japanese species and phylotypes of Gambierdiscus, the effects of light intensity on their growth were tested, using a photoirradiation-culture system. The relationship between the observed growth rates and light intensity conditions for the four species/phylotypes were formulated at R > 0.92 (p < 0.01) using regression analysis and photosynthesis-light intensity (P-L) model. Based on this equation, the optimum light intensity (L_max) and the semi-optimum light intensity range (L_s-opt) that resulted in the maximum growth rate (μ_max) and ≥80% μ _max values of the four species/phylotypes, respectively, were as follows: (1) the L_max and L_s-opt of G. australes were 208 μmol photons m⁻² s⁻¹ and 91–422 μmol photons m⁻² s⁻¹, respectively; (2) those of G. scabrosus were 252 and 120–421 μmol photons m⁻² s⁻¹, respectively; (3) those of Gambierdiscus sp. type 2 were 192 and 75–430 μmol photons m⁻² s⁻¹, respectively; and (4) those of Gambierdiscus sp. type 3 were ≥427 and 73–427 μmol photons m⁻² s⁻¹, respectively. All four Gambierdiscus species/phylotypes required approximately 10 μmol photons m⁻² s⁻¹ to maintain growth. The light intensities in coastal waters at a site in Tosa Bay were measured vertically at 1 m intervals once per season. The relationships between the observed light intensity and depth were formulated using Beer’s Law. Based on these equations, the range of the attenuation coefficients at Tosa Bay site was determined to be 0.058–0.119 m⁻¹. The values 1700 μmol photons m⁻² s⁻¹, 500 μmol photons m⁻² s⁻¹, and 200 μmol photons m⁻² s⁻¹ were substituted into the equations to estimate the vertical profiles of light intensity at sunny midday, cloudy midday and rainy midday, respectively. Based on the regression equations coupled with the empirically determined attenuation coefficients for each of the four seasons, the ranges of the projected depths of L_max and L_s-opt for the four Gambierdiscus species/phylotypes under sunny midday conditions, cloudy midday conditions, and rainy midday conditions were 12–38 m and 12–54 m, 1–16 m and 1–33 m, and 0 m and 0–16 m, respectively. These results suggest that light intensity plays an important role in the bloom dynamics and vertical distribution of Gambierdiscus species/phylotypes in Japanese coastal waters.     

Novel nicotine analogues with potential anti-mycobacterial activity

Tuberculosis (TB) is the second leading lethal infectious disease in the world after acquired immuno deficiency (AIDs). We have developed a series of twenty-five novel nicotine analogues with de-addiction property and tested them for their activity against Mycobacterium tuberculosis (MTB). In an effort to increase the specificity of action and directing nicotine analogues to target MTB, four promising compounds were further optimized via molecular docking studies against the Dihydrofolate reductase of MTB. After lead optimization, one nicotine analogue [3-(5-(3fluorophenyl)nicotinoyl)-1-methylpyrrolidin-2-one] exhibited minimum inhibitory concentration of 1 μg/mL (2.86 nM) against M. tuberculosis (H37Rv strain), a human pathogenic strain of clinically significant importance. Pharmacokinetic analysis of [3-(5-(3fluorophenyl)nicotinoyl)-1methylpyrrolidin-2-one] with lowest MIC value via oral route in Wistar rats revealed that at a dosage of 5 mg/kg body weight gave a maximum serum drug concentration (C_max) of 2.86 μg/mL, T_max of one hour and a half-life (T_1/2) of more than 24 h and Volume of distribution (V_d) of 27.36 L. Whereas the parenteral (intra venous) route showed a C_max of 3.37 μg/mL, T_max of 0.05 h, T_1/2 of 24 h and V_d equivalent to 23.18 L. The acute oral toxicity and repeated oral toxicity studies in female Wistar rats had an LD₅₀ > 2000 mg/kg body weight. Our data suggests that nicotine derivatives developed in the present study has good metabolic stability with tunable pharmacokinetics (PK) with therapeutic potential to combat MTB. However, further in vivo studies for anti-tuberculosis activity and elucidation of mode of action could result in more promising novel drug for treating MTB. To the best of our knowledge this is the first report revealing the anti-mycobacterial potential of nicotine analogue at potential therapeutic concentrations.     

Kinetics of cellulose hydrolysis by halostable cellulase from a marine Aspergillus niger at different salinities

Kinetics of cellulose hydrolysis with halostable cellulase from a marine Aspergillus niger was analyzed at different salinities. Cellulase activity in 8% NaCl solution was 1.43 folds higher than that in NaCl free solution. Half saturation constant, K_m (15.6260 g/L) and the rate constant of deactivation, K_de (0.3369 g/L h) in 8% NaCl solution was lower than that (18.6364 g/L), 0.3754 (g/L h) in NaCl free solution. The maximum initial hydrolysis velocity, V_max (25.5295 g/L h), in 8% NaCl solution was higher than that in NaCl free solution (25.0153 g/L h). High salinity increased affinity to the cellulase to the substrate and thermostability. Halostable cellulase from a marine Aspergillus niger was valuable for cellulose hydrolysis under high salinity conditions.     

Phosphorus retention capacity of agricultural headwater ditch sediments under alkaline condition in purple soils area,China

Phosphorus (P) retention by headwater ditch sediments adsorption plays a pivotal ecological role in P buffering in freshwater ecosystems. Previous studies focused on headwater ditch sediment adsorption and its P retention capacity in acid conditions, but little information is available for headwater ditches under alkaline condition. In this study, adsorption behavior of phosphorus was investigated in headwater ditch sediments under alkaline condition using a batch equilibrium technique, thus determining phosphorus retention capacity of headwater ditch sediments collected at 11 sites at base-flow on 2 March 2006 in purple soils area of China. Results showed that headwater ditch sediments had elevated phosphorus sorption maximum (S_max) values (122.72–293.23 mg P kg^?1) and P binding energy (K) values (1.64–8.65 L mg^?1), while they had low equilibrium phosphorus concentration (EPC₀) (0.001–0.108 mg L^?1) and degree of phosphorus saturation (DSP) (1.93–10.19%). Analysis of EPC₀ and soluble P concentration indicated that sediments acted as a sink for P across all headwater ditches. Therefore, there were high intrinsic P retention capacities of headwater ditch sediments. Positive correlations of both K and S_max with oxalate-extractable Fe (r of 0.93 and 0.81, p < 0.05) and total carbon (TC) (r of 0.89 and 0.74, p < 0.05) were found, thus suggesting that organic matter and amorphous or poorly crystalline Fe would play dominant roles in P adsorption in the headwater ditch sediments under alkaline condition. Since neither S_max nor K were correlated with CCE (CaCO₃) (r of 0.15 and ?0.06, p > 0.05), the high-energy sorptive surfaces of Fe oxides were more important than CaCO₃ in P sorption of sediment under alkaline condition. At the same time, these poor correlations between CCE and K and S_max imply a non-linear relationship between P retention and the content of carbonate. The negative correlations of both K and S_max with pH (r of–0.73, and–0.58, p < 0.05) revealed that an increase in pH would not improve sediment retention capacity under alkaline conditions.     

The influence of starvation on fast-start performance of Spinibarbus sinensis

Juvenile Spinibarbus sinensis (n = 48, body length, 5.86 ± 0.10 cm, 25 °C) were fasted for 0, 0.5, 1, 2, 4 and 6 weeks. The fast-start performances of the experimental fish were assessed using high-speed video photography and the locomotive kinematics analysis. The morphological parameters including tail height (H₂), tail length (L₂), lateral body area (S₁), median fin area (S₂), dorsal cross section area (S₃) and tail cross section area (S₄) were also measured using TpsDig and the Photoshop. The results showed that 6 week starvation resulted in significant decreases in the escape distance (d), maximum linear velocity (V_max) and maximum linear acceleration (a_max) of center of mass in Stage 1 and Stage 2 of fast-start process (P < 0.05), however there were two relatively sTable phases in the V_max and d, during the week 1–2 (V_max = 0.67 ± 0.06 mm/ms; d = 8.86 ± 0.73 mm) and week 4–6 (V_max = 0.31 ± 0.04 mm/ms; d = 3.70 ± 0.56 mm). When compared with the control group (0 week starvation group), only the 6 week starvation group showed the significantly different response time (t) with average t = 9.20 ± 0.37 ms in week 1–4. There were no significant difference in mass center turning angles at first stage (T_a1) , second stage (T_a2) and the sum of two stages (T_a(1+2)) was also not different (P > 0.05). The fish did not show any directional preference for left or right during escape turning, and all of the related parameters also remained unchanged among treatment group (P > 0.05). The areas of dorsal body cross-section decreased more acutely (P < 0.05) than caudal body cross-section (45.4% vs 38.0%) during the entire starvation period while no significant differences were observed in both the tail height and tail length among all treatment groups (P > 0.05). The results indicated that fast-start performance of juvenile S. sinensis is affected by the starvation; metabolic energy related traits such as the maximum linear velocity and the maximum linear acceleration decreased significantly after starvation; whereas traits with no direct link to metabolic energy such as the response time and turning angle remained unchanged during starvation. The lack of starvation induced change in the maneuverability of the fish suggests that fast-start ability related to escape strategy is relatively well conservative in juvenile S. sinensis.     

Determination of asiatic acid in beagle dog plasma after oral administration of Centella asiatica extract by precolumn derivatization RP-HPLC

A novel precolumn derivatization reversed-phase high-performance liquid chromatography (RP-HPLC) method with UV–vis detection for the quantitative determination of total concentration of asiatic acid (AA) in beagle dog plasma is described. AA was extracted with n-hexane-dichloromethane-2-propanol (20:10:1, v/v/v) from plasma, which had been hydrolyzed by acid and derivatized with p-Toluidine. Chromatographic separation was achieved on a C₁₈ column using gradient elution in a water–methanol system. Detection was set at UV wavelength of 248 nm. A calibration curve ranging from 0.01 to 1.5 μg/mL was shown to be linear, and the lower limit of quantification (LLOQ) was 0.01 μg/mL. The intra- and inter-day precisions which were determined by three different concentrations (0.05, 0.2 and 0.8 μg/mL) ranged from 4.4% to 13.1% and 4.6% to 14.2%, respectively. Mean extraction recoveries were no less than 65% for AA and ursolic acid (IS). Plasma samples containing asiatic acid were stable for 30 days at ?20 °C. The method was successfully applied to a pharmacokinetic study in beagle dogs after oral administration of Centella asiatica extract, and the main pharmacokinetic parameters obtained were: T_1/2, 4.29 h; T_max, 2.70 h; C_max, 0.74 μg/mL; AUC_0–t and AUC_0–∞, 3.74 and 3.82 μg h/mL, respectively.     

Effects of temperature on purification of eutrophic water by floating eco-island system

The effects of temperature on pollutant removal of two plant species (Oenanthe javanica D.C. and Nasturtium officinale) were evaluated using simulated microcosms of the floating eco-island system (FEIS). Both the planted FEIS (P-FEIS) and the non-planted FEIS (NP-FEIS) dramatically decreased NH₄–N concentration in the hypereutrophic water at low (10 °C), medium (22 °C), and high (35 °C) temperatures, and to a greater extent for the P-FEIS and at medium temperature. The NO₂–N concentration was effectively decreased from 0.23 to 0.01 mg/L after 4 d treatment with the P-FEIS at all the three temperatures, but was slightly increased in the NP-FEIS at low temperature. The P-FEIS could decrease NO₃–N concentration in the eutrophic water over 1–3 times depending on temperature, with greater decrease at high temperature. The remove of total P (TP) reached 78%, on average, with the FEIS treatment for 4 d at all temperatures, which was over three times greater than those with the NP-FEIS at low temperature. The removal rates of Chla, COD_Mn, and BOD₅ by the P-FEIS from the hypereutrophic water were, on average, 70%, 85%, 83% at 22 °C and 35 °C, respectively, while over 1–2 times smaller at 10 °C. More effective removals of Chla, COD_Mn, and BOD₅ (over 1–2 times) were noted with the P-FEIS than those with the NP-FEIS. N. officinale showed more efficiency in removing ammonium and TN at low temperature, and BOD₅ at medium and high temperatures, as compared to O. javanica. Whereas O. javanica could more effectively decrease Chla at 22 °C and 35 °C and COD_Mn at 10 °C than N. officinale after 4 d treatment. Higher dissolved oxygen concentration and pH was found in the FEIS with N. officinale than that with O. javanica D.C. The results imply that plant eco-island system had remarkable purification ability to remove pollutants from hypereutrophic water, and mixed planting of O. javanica D.C. with N. officinale on the FEIS may enhance nutrient removal and water quality improvement of eutrophic water bodies, especially at low temperature season.     

A comparative study of the use of inorganic carbon resources by Chara aspera and Potamogeton pectinatus

We studied the potential role of dissolved inorganic carbon (DIC) in determining vegetation dominance of Potamogeton pectinatus L. and Chara aspera Deth. ex Willd. by monitoring the seasonal dynamics of DIC in a shallow lake and comparing the use of DIC of the two species. The HCO₃⁻-concentration in summer dropped from 2.5 to <0.5 mM with seasonally increasing Chara biomass, whereas outside the vegetation concentrations remained at 2.5 mM. Inside Potamogeton spp. vegetation DIC decreased from 2.5 to ca. 0.75 mM HCO₃⁻. A growth experiment showed ash-free biomass for P. pectinatus was nearly two times as high as for C. aspera at 3 mM HCO₃⁻, but almost two times lower at 0.5 mM than at 3.0. In a separate experiment, P. pectinatus precultured at a relatively low HCO₃⁻-level had a lower net photosynthetic rate (P_max, 0.1 mmol O₂ g⁻¹ DW h⁻¹) than C. aspera (P_max, 0.1 mmol O₂ g⁻¹ DW h⁻¹) over the range of HCO₃⁻-concentrations tested (P_max, 0.14 mmol O₂ g⁻¹ DW h⁻¹). In response to CO₂ no significant differences between the compensation points (P. pectinatus, 28 mM; C. aspera 66 mM), were observed, but the photosynthetic rate increased faster than for C. aspera than for P. pectinatus. Under field conditions, the use of CO₂ is not important since inside vegetation CO₂-concentrations were below 10 μM, and thus, not available for photosynthesis of either species during the main part of the growth season. It is suggested that C. aspera may be a better competitor for HCO₃⁻ than P. pectinatus in conditions with a low HCO₃⁻ supply. As HCO₃⁻ is a strong limiting factor for growth inside the vegetation and probably the only carbon source available, the superior ability of C. aspera to use HCO₃⁻ may be an important factor explaining its present dominance in Veluwemeer.     

Elevated CO2 alleviates negative effects of salinity on broccoli (Brassica oleracea L. var Italica) plants by modulating water balance through aquaporins abundance

In the global change scenario, increased CO₂ may favour water use efficiency (WUE) by plants. By contrast, in arid and semiarid areas, salinity may reduce water uptake from soils. However, an elevated WUE does not ensure a reduced water uptake and upon salinity this fact may constitute an advantage for plant tolerance. In this work, we aimed to determine the combined effects of enhanced [CO₂] and salinity on the plant water status, in relation to the regulation of PIP aquaporins, in the root and leaf tissues of broccoli plants (Brassica oleracea L. var Italica), under these two environmental factors. Thus, different salinity concentrations (0, 60 and 90 mM NaCl) were applied under ambient (380 ppm) and elevated (800 ppm) [CO₂]. Under non-salinised conditions, stomatal conductance (G_s) and transpiration rate (E) decreased with rising [CO₂] whereas water potential (Ψ_ω) was maintained stable, which caused a reduction in the root hydraulic conductance (L₀). In addition, PIP1 and PIP2 abundance in the roots was decreased compared to ambient [CO₂]. Under salinity, the greater stomatal closure observed at elevated [CO₂] – compared to that at ambient [CO₂] – caused a greater reduction in G_s and E and allowed plants to maintain their water balance. In addition, a lower decrease in L₀ under salt stress was observed at elevated [CO₂], when comparing with the decrease at ambient [CO₂]. Modifications in PIP1 and PIP2 abundance or their functionality in the roots is discussed. In fact, an improved water status of the broccoli plants treated with 90 mM NaCl and elevated [CO₂], evidenced by a higher Ψ_ω, was observed together with higher photosynthetic rate and water use efficiency. These factors conferred on the salinised broccoli plants greater leaf area and biomass at elevated [CO₂], in comparison with ambient [CO₂]. We can conclude that, under elevated [CO₂] and salt stress, the water flow is influenced by the tight control of the aquaporins in the roots and leaves of broccoli plants and that increased PIP1 and PIP2 abundance in these organs provides a mechanism of tolerance that maintains the plant water status.     

A novel control of enzymatic enantioselectivity through the racemic temperature influenced by reaction media

The influence of reaction media on the racemic temperature (T_r) in the lipase-catalyzed resolution of ketoprofen vinyl ester was investigated. An effective approach to the control of the enzymatic enantioselectivity and the prediction of the increasing tendency was developed based on the T_r influenced by reaction media. The T_r for the resolution catalyzed by Candida rugosa lipase (CRL) was found at 29 °C in aqueous and S-ketoprofen was obtained predominantly at 40 °C. However, CRL showed R-selectivity at 40 °C in diisopropyl ether because the T_r was changed to 56 °C. CRL, lipase from AYS Amano^® and Mucor javanicus lipase were further applied for the investigation of the enzymatic enantioselectivity in dioxane, DIPE, isooctane and their mixed media with water. The effects of the reaction medium on T_r could be related to the solvent hydrophobicity, the lipase conformational flexibility and the interaction between the enantiomers and the lipase.     

Efficient preparation of enantiopure l-tert-leucine through immobilized penicillin G acylase catalyzed kinetic resolution in aqueous medium

Racemic _DL-tert-leucine (_DL-Tle) was resolved to obtain enantiopure _L-Tle through enantioselective hydrolysis of its N-phenylacetyl derivative with immobilized penicillin G acylase (PGA). The effects of pH, reaction temperature, substrate concentration and reaction time on the reaction were investigated. The reaction was conveniently carried out at 0.4 M substrate concentration in water at pH 8.0 and 30 °C. Under the optimized reaction conditions, _L-Tle was obtained in an enantiopure form (>99% ee) with 45.8% substrate conversion after 4 h. The thermal stability and operational stability of immobilized PGA were examined. Furthermore, the preparation of _L-Tle was successfully performed in a recirculating packed bed reactor (RPBR) system and immobilized PGA exhibited a long-term stability for 51 days with a slight decrease of activity. The isolated _D-enantiomer was racemized at 160 °C for 15 min and reused as substrate. The results obtained clearly demonstrated a potential for industrial application of immobilized PGA in the preparation of _L-Tle through enantioselective hydrolysis of its N-phenylacetyl derivative.     

Thermoregulation on the air–water interface—II: Foot conductance,activity metabolism and a two-dimensional heat transfer model

We used a quasi-adiabatic calorimeter and respirometry apparatus to measure heat loss from the feet of 3- to 4-d-old mallard ducklings (Anas platyrhynchos). We found that, at cool (<20 °C) operative temperatures, foot conductance increased in proportion to operative temperature, T_e, rather than water temperature. We combined these results with those of an earlier study to develop a heat transfer model for swimming ducklings. This model includes separate thermal conductances to air (0.027 W/°C-animal), to water through the down (0.035[1+2.05×10⁻⁷T_e⁴]) W/°C-animal, and to water through the feet (2.01×10⁻⁸T_e⁴ W/°C-animal). The overall conductance by all three routes is only 21% greater when swimming compared to standing in air at the same operative temperature. Interestingly, ducklings can maintain body temperature >39 °C while swimming in 5 °C water, but not when restrained in a calorimeter with 5 °C water. Peak oxygen consumption is greater when swimming, and apparently exercise metabolism substitutes almost completely for thermoregulatory heat production.     

Performance evaluation of various bioreactors for the removal of Cr(VI) and organic matter from industrial effluent

Performances of various bioreactors under different operating conditions were evaluated with respect to hexavalent chromium (Cr(VI)) reduction and COD removal. Continuous reactor studies were carried out with (i) aerobic suspended growth system, (ii) aerobic attached growth system, and (iii) anoxic attached growth system, using both synthetic and actual industrial wastewater. Arthrobacter rhombi-RE (MTCC7048), a Cr(VI) reducing strain enriched and isolated from chromium contaminated soil, was used in all the bioreactors for Cr(VI) biotransformation and COD removal. Aerobic and anoxic batch experiments were conducted to evaluate the bio-kinetic parameters. The bio-kinetic parameters for aerobic system were: μ_max = 2.34/d, K_s = 190 mg/L (as COD), K_i = 3.8 mg/L of Cr(VI), and Y_T = 0.377. These parameters for anoxic conditions were: μ_max = 0.57/d, K_s = 710 mg/L (as COD), K_i = 8.77 mg/L of Cr(VI), and Y_T = 0.13. Aerobic attached growth system, operated at a hydraulic retention time (HRT) of 24 h and an organic loading rate (OLR) of 3 kg/m³/d, performed better than aerobic suspended and the anoxic attached growth systems operated under identical conditions, while treating synthetic wastewater as well as industrial effluent.