Kinetic Study and Mathematical Modeling of Chromium(VI) Reduction and Microorganism Growth Under Mixed Culture

The kinetics of chromium(VI) reduction by Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) was studied under both pure and mixed cultures. Initially, the study of kinetics was performed in pure culture. It was observed that the growth of the two bacteria was both inhibited in the presence of chromium(VI). The maximum specific growth rate (μ _m ) of P. aeruginosa decreased from 2.3942 h^?1 (without Cr(VI)) to 1.8551 h^?1 (with Cr(VI)). Under the mixed culture, the growth of E. coli was inhibited by P. aeruginosa. The maximum specific growth rate (μ _m ) of E. coli decreased form 0.871 h^?1 (in pure culture) to 0.153 h^?1 (in mixed culture). When the concentration of each bacterium was 4.5 × 10⁸ cells ml^?1, the half-velocity reduction rate constant (K _C) and the maximum specific reduction rate constant (v _max) of chromium(VI) were 80.05 mg chromium(VI) l^?1 and 3.674 mg chromium(VI) cells^?1 h^?1, respectively. The results showed that the simulation appeared in good agreement with the experimental data, supporting the series of mathematical models represented the bacteria growth and chromium(VI) reduction in both pure and mixed cultures usefully.     

EVALUATION OF COMPETITIVE ABILITY OF STAURASTRUM LUETKEMUELLERII (CHLOROPHYCEAE) AND MICROCYSTIS AERUGINOSA (CYANOPHYCEAE) UNDER P LIMITATION1

The desmid Staurastrum luetkemuellerii Donat et Ruttner and the cyanobacterium Microcystis aeruginosa Kütz. showed pronounced differences in chemical composition and ability to maintain P fluxes. The cellular P:C ratio (Q_p) and the surplus P:C ratio (Q_sp) were higher in M. aeruginosa, indicating a lower yield of biomass C per unit of P. The subsistence quota (Q_p) was 1.85 μg P·mg C^?1in S. luetkemuellerii and 6.09 μg P·mg C^?1in M. aeruginosa, whereas the respective Q_p of P saturnted organisms (Q_s) were 43 and 63 μg P·mg C^?1. These stores could support four divisions in S. luetkemuellerii and three divisions in M. aeruginosa, which suggests that the former exhibited highest storage capacity (Q_s/Q₀). M. aeruginosa showed a tenfold higher activity of alkaline phosphatase than S. luetkemuellerii when P starved. The optimum N:P ratio (by weight) was 5 in S. luetkemuellerii and 7 in M. aeruginosa. The initial uptake of P_i pulses in the organisms was not inhibited by rapid (<1 h) internal feedback mechanisms and the short term uptake rote could be expressed solely as a function of ambient P_i. The maximum cellular C-based uptake rate (V_m) in P starved M. aeruginosa was up to 50 times higher than that of S. luetkemuellerii. It decreased with increasing growth rate (P status) in the former species and remained fairly constant in the latter. The corresponding cellular P-based value (U_m= V_m/Q_p) decreased with growth rate in both species and was about 10 times higher in P started M. aeruginosa than in S. luetkemuellerii. The average half saturation constant for uptake (K_m) was equal for both species (22 μg P·L^?1) and varied with the P status. S. luetkemuellerii exhibited shifts in the uptake rate of P_i that were characterized by increased affinity (U^m/K^m) at low P_i, concentrations (<4 μg P·L^?1) compared to that at higher concentrations. The species thus was well adapted to uptake at low ambient P_i, but M. aeruginosa was superior in P_i uptake under steady state and transient conditions when the growth rate was lower than 0.75 d^?1. Moreover, M. aeruginosa was favored by pulsed addition of P_i. M. aeruginosa relpased P_i at a higher rate than S. luetkemuellerii. Leakage of P_i from the cells caused C-shaped μ vs. P_i curves. Therefore, no unique K_s for growth could be estimated. The maximum growth rate (μ_m) (23° C) was 0.94 d^?1for S. luetkemuellerii and 0.81 d^?1for M. aeruginosa. The steady state concentration of P_i (P*) was lower in M. aeruginosa than in S. luetkemuellerii at medium growth rates. The concentration of P_i at which the uptake and release of P_i was equal (P_c was, however, lower in S. luetkemuellerii.     

Enterotoxigenic Escherichia coli in sewage‐impacted waters and aquatic weeds: quantitative PCR for culture‐independent enumeration

Aim: To develop quantitative PCR for culture‐independent enumeration of enterotoxigenic Escherichia coli (ETEC) in sewage‐impacted waters and aquatic weeds. Methods and Results: Two fluorescent probes (TaqMan and FRET) based on two different real‐time PCR chemistries were designed in highly conserved region of LT1 gene encoding heat labile enterotoxin. Both the assays could detect 2 CFU ml^?1 from serially diluted (two‐fold and ten‐fold) culture of reference strain (E. coli MTCC 723). FRET performed better in terms of C_T value and PCR efficiency than TaqMan. The presence of 10⁶ CFU ml^?1 of nonpathogenic E. coli reduced the detection limit two‐fold with both the probes. However, the performance for two chemistries in various environmental samples was significantly (student’s t‐test, P < 0·05) different. Conclusion: It could be inferred from this study that real‐time PCR chemistries (TaqMan and FRET) could detect very few copies of target DNA in pure cultures, but may give varied response in the presence of nonspecific DNA and natural inhibitors present in environmental sample matrices. Significance and Impact of the Study: The assays can be used for pre‐emptive monitoring of aquatic weeds (a potential nonpoint source), surface and potable waters to prevent waterborne outbreaks caused by ETEC.     

Mixed Phase Solid‐State Plastic Crystal Electrolytes Based on a Phosphonium Cation for Sodium Devices

Na batteries are seen as a feasible alternative technology to lithium ion batteries due to the greater abundance of sodium and potentially similar electrochemical behavior. In this work, mixed phase electrolyte materials based on solid‐state compositions of a tri methylisobutylphosphonium (P_111i4) bis(tri fluromethanesulphonyl)amide (NTf₂) organic ionic plastic crystal (OIPC) and high concentration of NaNTf₂ that support safe, sodium metal electrochemistry are demonstrated. A Na symmetric cell can be cycled efficiently, even in the solid state (at 50 °C and 60 °C), for a 25 mol% (P_111i4NTf₂)–75 mol% NaNTf₂ composition at 0.1 mA cm^?2 for 100 cycles. Thus, these mixed phase materials can be potentially used in Na‐based devices under moderate temperature conditions. It is also investigated that the phase behavior, conductivity, and electrochemical properties of mixtures of NaNTf₂ with this OIPC. It is observed that these mixtures have complex phase behavior. For high compositions of the Na salt, the materials are solid at room temperature and retain a soft solid consistency even at 50 °C with remarkably high conductivity, approaching that of the pure ionic liquid at 50 °C, i.e., 10^?3–10^?2 S cm^?1.     

Synthesis, characterization, and antibacterial and anticancer screening of {M2+–Co3+–M2+} and {Co3+–M2+} (M?is?Zn, Cd, Hg) heterometallic complexes

The cobalt(III) complexes Et₄N[Co(L¹)₂] and [Co(L²)₃] [H₂L¹ is 2,6-bis(N-(2-pyridyl)carbamoyl)pyridine and HL² is 2-(N-(2-pyridyl)carbamoyl)pyridine] were used as the building blocks for preparing a series of {M²⁺?CCo³⁺?CM²⁺} (where M?is?Zn, Cd, or Hg) and {Co³⁺?CM²⁺} (where M?is?Zn or Cd) heterometallic complexes. All heterometallic complexes were characterized using a host of spectroscopic methods (IR, NMR, and UV/vis spectroscopy and mass spectrometry), elemental analysis, and conductivity measurements. One of the representative compounds, {Hg²⁺?CCo³⁺?CHg²⁺}, was characterized crystallographically, and it was revealed that two Hg(II) ions are coordinated within the clefts created by the building block Et₄N[Co(L¹)₂]. The results of screening for anticancer activity against the human brain tumor U87 cell line and antibacterial activity against a range of resistant (Pseudomonas aeruginosa and Proteus vulgaris) as well as standard (Staphylococcus aureus SA 96, P. aeruginosa MTCC 1688, Klebsiella planticola MTCC 2272, and Escherichia coli T7) bacterial strains indicate promising activities. Notably, the observed activity was found to vary with the type of building block and the secondary metal ion present in the heterometallic complex. Treatment-induced cell death [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT and macrocolony assay), growth inhibition, cytogenetic damage, cell cycle delay, and apoptosis were studied as the parameters for cellular response.     

Competitive dominance of the cyanobacterium Microcystis aeruginosa in nutrient-rich culture conditions with special reference to dissolved inorganic carbon uptake

The aim of the present study was to determine what factors contribute to the competitive advantage of cyanobacteria in eutrophic conditions. Mixed species batch culture experiments were conducted at three pHs (8.2, 8.8, 10.2) and irradiances (30, 90, 180 μmol photons m^?2 s^_1) between Microcystis aeruginosa Kützing and Staurastrum dorsidentiferum W. et West or Synedra ulna (Nitzsch) Ehrenberg, which always resulted in the dominance of M. aeruginosa. The final yields of competitors were often significantly lower than when cultured singly. The dominance of the surface‐loving M. aeruginosa appears to be related to its advantageous C0₂ uptake. To clarify the importance of dissolved inorganic carbon (DIC) as a selective factor, the effect of aeration was examined with M. aeruginosa. The growth of M. aeruginosa quickly stopped in nonaerated conditions, while it continued growing throughout the culture when aerated. This result indicates that DIC limitation easily occurs in static conditions and the viewpoint of C0₂ exchange efficiency would be helpful in discussing the competitive advantage of M. aeruginosa. When the three species were cultured at various ratios of surface area to volume (s/v), postulating it as an index of the gas exchange efficiency, the increases in population densities strongly correlated with s/v, and the relationships between the specific growth rate and s/v corresponded well to a Monod type saturation function. We found that M. aeruginosa had the lowest half‐saturation constant among the three, reflecting its high affinity for DIC.     

Changes in NO3− and K+ uptake by four species in flowing solution culture in response to increased irradiance

Net rates of NO₃^? and K⁺ uptake were compared for oilseed rape (Brassica napus L. cv. Jet neuf), perennial ryegrass (Lolium perenne L. cv. S23), Italian ryegrass (Lolium multiflorum Lam. cv. Augusta) and wheat (Triticum aestivum L. cv. Fen-man) in flowing solution culture during a 4-day sequence of low-low-high-high natural irradiance. Concentrations of NO₃^? (10 μM) and K⁺ (2.5 μM) in solutions were maintained automatically and hourly variation in net uptake of these ions was measured. During the 2 days of low irradiance (<1 MJ m^?2 day^?1) the uptake rates of both ions by all species were low at <1 mmol NO₃^?, m^?2 h^?1 and <0.4 mmol K⁺ m^?2 h^?1. Uptake increased in each species during the first day of high irradiance (7.90 MJ m^?2 day^?1) to >4 mmol NO₃^? m^?2 h^?1 and >1.4 mmol K⁺ m^?1 h^?1. These higher rates were maintained throughout the following night. The lag-time between maximum irradiance and the onset of the highest acceleration in uptake was greater for NO₃^? (5–8 h) than for K⁺ (≤1 h) in rape, wheat and Italian ryegrass. Uptake of NO₃^?, by perennial ryegrass showed an almost constant acceleration for 18 h following maximum irradiance. In all species the measured maximum inflows (uptake rate per unit root length) of both ions were greater than theoretical maximum potential inflows to a non-competing infinite-sink root in soil, by factors of 7 and 36, respectively, for NO₃^? and K⁺, averaged over all species.     

Batch- and continuous-culture studies of a methane-utilizing mixed culture

A methane-utilizing mixed culture isolated from activated sludge by selective enrichment at 45°C was found to consist of three interacting species: a methaneutilizing bacterium, a citrate-utilizing bacterium, and a methanol-utilizing bacterium. All three species grew well at 45°C. Three different stable mixed cultures were reconstituted by various combinations of these pure cultures. The nutritional requirements and substrate ranges for each pure culture were determined. The nutritional requirements and substrate ranges for each pure culture were determined. The saturation constant for the methane-utilizing bacterium on methane (K) and for the methanol-utilizing bacterium on methanol (K) were 1.73 × 10^?6M and 4.51 × 10^?7M, respectively. The volumetric mass transfer coefficient for methane (K_L a) was determined to be 65.6 hr^?1.     

Impact of light quality on a native Louisiana Chlorella vulgaris/Leptolyngbya sp. co‐culture

Light effect on cultures of microalgae has been studied mainly on single species cultures. Cyanobacteria have photosynthetic pigments that can capture photons of wavelengths not available to chlorophylls. A native Louisiana microalgae (Chlorella vulgaris ) and cyanobacteria (Leptolyngbya sp.) co‐culture was used to study the effects of light quality (blue–467 nm, green–522 nm, red–640 nm and white–narrow peak at 450 nm and a broad range with a peak at 550 nm) at two irradiance levels (80 and 400 μmol m^?2 s^?1) on the growth, species composition, biomass productivity, lipid content and chlorophyll‐a production. The co‐culture shifted from a microalgae dominant culture to a cyanobacteria culture at 80 μmol m^?2 s^?1. The highest growth for the cyanobacteria was observed at 80 μmol μmol m^?2 s^?1 and for the microalgae at 400 μmol m^?2 s^?1. Red light at 400 μmol m^?2 s^?1 had the highest growth rate (0.41 d^?1), biomass (913 mg L^?1) and biomass productivity (95 mg L^?1 d^?1). Lipid content was similar between all light colors. Green light had the highest chlorophyll‐a content (1649 μg/L). These results can be used to control the species composition of mixed cultures while maintaining their productivity.     

Radiation Chemistry of Foods

An intermediate radical, ?H₂OH, was produced in aqueous methanol solution containing nitrous oxide by γ-irradiation. Yields of ethylene glycol and formaldehyde, the major and the minor product from ?H₂OH, respectively, changed on the addition of some solutes. Cysteine lowered the both product yields to zero even at a low concentration of 5 × 10^?5m. Oxygen of low concentrations (2.5~7.5 × 10^?5 m) changed effectively the major product from ethylene glycol to formaldehyde. k _(CySH+?H2OH)/k_(O2+?H2OH) was calculated as 0.5.

Ascorbic acid (5 × 10^?5 m) lowered ethylene glycol yield to 48%, cystine (10^?3m) to 15%, methionine (10^?3m) to 31%, histidine (10^?3m) to 42%, tryptophan (10^?3m) 46%, tyrosine (10^?3m) to 77%, phenylalanine (10^?3m) to 73%, hypoxanthine (10^?3m) to 37%, adenine (10^?3m) to 52%, uracil (10^?3m) to 20%, thymine (10^?3m) to 10%, cytosine (10^?3 m) to 49%, rutin (10^?3m) to 23%, pyrogallol (10^?3m) to 41%, and gallic acid (10^?3m) to 78% of the control. These results suggest that the reactions of the secondary radicals such as ?H₂OH perform an important role in material change of foods irradiated with γ rays.     

Effect of temperature on ethanol tolerance of thermotolerant Isshatchenkia orientalis IPE100

Tolerance to high temperature and ethanol is a major factor in high‐temperature bio‐ethanol fermentation. The inhibitory effect of exogenously added ethanol (0–100 g L^?1) on the growth of the newly isolated thermotolerant Issatchenkia orientalis IPE100 was evaluated at a range of temperatures (30–45°C). A generalized Monod equation with product inhibition was used to quantify ethanol tolerance, and it correlated well with the experimental data on microbial growth inhibition of ethanol at the temperatures of 30–45°C. The maximum inhibitory concentration of ethanol for growth (P_m) and toxic power (n) at the optimal growth temperature of 42°C were estimated to be 96.7 g L^?1 and 1.23, respectively. The recently isolated thermotolerant I. orientalis IPE100 shows therefore a strong potential for the development of future high‐temperature bio‐ethanol fermentation technologies. This study provides useful insights into our understanding of the temperature‐dependent inhibitory effects of ethanol on yeast growth.     

Photosynthetic characteristics of female vegetative tissues of Porphyra katadai var. hemiphylla (Bangiales, Rhodophyta) in culture

In this study, chlorophyll fluorescence parameters (?F/F _m′, F _v/F _m) and oxygen evolution of female vegetative tissues of Porphyra katadai var. hemiphylla in unisexual culture (FV) and in mixed culture with male vegetative tissues (FV-M) were followed at 5–20 °C, 10 and 80 μmol photons m^?2 s^?1. The formation of reproductive tissues was closely correlated with decreasing photosynthetic activities. At the same temperature the tissues cultured under 80 μmol photons m^?2 s^?1 showed a greater extent of maturation than those under 10 μmol photons m^?2 s^?1, and their decrease in photosynthesis was also larger. Under the same light intensity the extent of maturation increased with increasing temperature, and both cultures showed higher values of ?F/F _m′ and F _v/F _m at 10 and 15 °C, while their oxygen evolution became negative at 15–20 °C during the later period. Under the same culture condition the maturation of FV-M culture was relatively faster than that of FV culture, while their photosynthetic activity, especially ?F/F _m′, was lower.     

Influence of stomatal distribution on transpiration in low-wind environments

Abstract According to computer energy balance simulations of horizontal thin leaves, the quantitative effects of stomatal distribution patterns (top vs. bottom surfaces) on transpiration (E) were maximal for sunlit leaves with high stomatal conductances (g_s) and experiencing low windspeeds (free or mixed convection regimes). E of these leaves decreased at windspeeds > 50 cm s^?1, despite increases in the leaf-to-air vapour density deficit. At 50 cm s^?1 wind-speed, rapidly transpiring leaves had greater E when one-half of the stomata were on each leaf surface (amphistomaty; 10.16 mmol H₂O m^?2 s^?1) than when all stomata were on either the top (hyperstomaty; 9.34 mmol m^?2s^?1) or bottom (hypostomaty; 7.02 mmol m^?2s^?1) surface because water loss occurred in parallel from both surfaces. Hyperstomatous leaves had larger E than hypostomatous leaves because free convection was greater on the top than on the bottom surface. Transpiration of leaves with large g, was greatest at windspeeds near zero when ～60–75% of the stomata were on the top surface, while at high windspeeds E was greatest with, 50% of the stomata on top. For leaves with low g_s, stomatal distribution exerted little influence on simulated E values. Laboratory measurements of water loss from simulated hypo-, hyper-, and amphistomatous leaf models qualitatively supported these predictions.     

Assessing biodegradation of furfuryl alcohol using <Emphasis Type="Italic">Pseudomonas putida</Emphasis> MTCC 1194 and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> MTCC 1034 and its kinetics

The biodegradation of furfuryl alcohol (FA) in shake flask experiments using a pure culture of Pseudomonas putida (MTCC 1194) and Pseudomonas aeruginosa (MTCC 1034) was studied at 30 °C and pH 7.0. Experiments were performed at different FA concentrations ranging from 50 to 500 mg/l. Before carrying out the biodegradation studies, the bacterial strains were acclimatized to the concentration of 500 mg/l of FA by gradually raising 100 mg/l of FA in each step. The well acclimatized culture of P. putida and P. aeruginosa degraded about 80 and 66% of 50 mg/l FA, respectively. At higher concentration of FA, the percentage of FA degradation decreased. The purpose of this study was to determine the kinetics of biodegradation of FA by measuring biomass growth rates and concentration of FA as a function of time. Substrate inhibition was calculated from experimental growth parameters using the Haldane equation. Data for P. putida were determined as µ _max ?=?0.23 h^?1, K _s ?=?23.93 mg/l and K _i ?=?217.1 mg/l and for P. aeruginosa were determined as µ _max ?=?0.13 h^?1, K _s ?=?21.3 mg/l and K _i ?=?284.9 mg/l. The experimental data were fitted in Haldane, Aiba and Edwards inhibition models.     

Kinetics and thermodynamics of catalysis and thermal inactivation of a novel α-amylase (Tp-AmyS) from Thermotoga petrophila

Abstract

This research is focussed on kinetic, thermodynamic and thermal inactivation of a novel thermostable recombinant α-amylase (Tp-AmyS) from Thermotoga petrophila. The amylase gene was cloned in pHIS-parallel1 expression vector and overexpressed in Escherichia coli. The steady-state kinetic parameters (V_max, K_m, k_cat and k_cat/K_m) for the hydrolysis of amylose (1.39?mg/min, 0.57?mg, 148.6?s^?1, 260.7), amylopectin (2.3?mg/min, 1.09?mg, 247.1?s^?1, 226.7), soluble starch (2.67?mg/min, 2.98?mg, 284.2?s^?1, 95.4) and raw starch (2.1?mg/min, 3.6?mg, 224.7?s^?1, 61.9) were determined. The activation energy (E_a), free energy (ΔG), enthalpy (ΔH) and entropy of activation (ΔS) at 98?°C were 42.9?kJ mol^?1, 74?kJ mol^?1, 39.9?kJ mol^?1 and ?92.3 J mol^?1 K^?1, respectively, for soluble starch hydrolysis. While ΔG of substrate binding (ΔG_E-S) and ΔG of transition state binding (ΔG_E-T) were 3.38 and ?14.1?kJ mol^?1, respectively. Whereas, EaD, Gibbs free energy (ΔG*), increase in the enthalpy (ΔH*) and activation entropy (ΔS*) for activation of the unfolding of transition state were 108, 107, 105?kJ mol^?1 and ?4.1 J mol^?1 K^?1. The thermodynamics of irreversible thermal inactivation of Tp-AmyS revealed that at high temperature the process involves the aggregation of the protein.     

Growth kinetics of top and bottom cultures of Saccharomyces spp. in a chemostat using sugarbeet molasses

Growth kinetics were evaluated for three yeast strains of the genus Saccharomyces. Two topfloating strains, SF 115 and SF 116 and one flocculant yeast SF 104 were analyzed in pure and mixed cultures in 1-liter continuous fermentation experiments in a chemostat. Growth was monitored for 72 h at 30°C in a medium containing sugarbeet molasses and 1.0 g/liter each of NH₄H₂PO₄ and urea. SF 115 and SF 116 were found to have lower μ_max values of 0.290 and 0.296 h^?1, respectively, than SF 104, which had a μ_max of 0.364 h^?1. The two top-floating yeasts (SF 115 and SF 116) demonstrated greater affinity for the substrate and utilized substrates at a greater rate. They have K₈ values of 4.03 × 10^?3 M and 3.798 × 10^?3 M, respectively, compared to 9.06 × 10^?3 M for SF 104. A mixed culture of SF 116 and SF and SF 104 was found to have a μ_max of 0.426 h^?1 with a K_s of 6.924 × 10^?3 M. SF 115 grown in mixed culture with SF 104 exhibited a μ_max of 0.473 h^?1 with a K_s of 7.975 × 10^?3 M. In both cases, the SF 104 was the dominant microbe in mixed culture systems.     

Serine hydroxymethyltransferase from the silkworm Bombyx mori: Identification,distribution, and biochemical characterization

Serine hydroxymethyltransferase (SHMT) catalyzes the interconversion of serine and tetrahydrofolate (THF) to glycine and methylenetetrahydrofolate. cDNA encoding Bombyx mori SHMT (bmSHMT) was cloned and sequenced. The deduced amino acid sequence consisted of 465 amino acids and was found to share homology with other SHMTs. Recombinant bmSHMT was overexpressed in Escherichia coli and purified to homogeneity. The enzyme showed optimum activity at pH 3.0 and 30°C and was stable under acidic conditions. The K_m and k_cat/K_m values for THF in the presence of Nicotinamide adenine dinucleotide phosphate (NADP⁺) were 0.055 mM and 0.081 mM^?1 s^?1, respectively, whereas those toward NADP⁺ were 0.16 mM and 0.018 mM^?1 s^?1 and toward l ‐serine were 1.8 mM and 0.0022 mM^?1 s^?1, respectively. Mutagenesis experiments revealed that His119, His132, and His135 are important for enzymatic activity. Our results provide insight into the roles and regulation mechanism of one‐carbon metabolism in the silkworm B. mori.     

Estimates of soil respiration and net primary production of three forests at different succession stages in South China

Soil respiration (heterotropic and autotropic respiration, R_g) and aboveground litter fall carbon were measured at three forests at different succession (early, middle and advanced) stages in Dinghushan Biosphere Reserve, Southern China. It was found that the soil respiration increases exponentially with soil temperature at 5 cm depth (T_s) according to the relation R_g=a exp(bT_s), and the more advanced forest community during succession has a higher value of a because of higher litter carbon input than the forests at early or middle succession stages. It was also found that the monthly soil respiration is linearly correlated with the aboveground litter carbon input of the previous month. Using measurements of aboveground litter and soil respiration, the net primary productions (NPPs) of three forests were estimated using nonlinear inversion. They are 475, 678 and 1148 g C m^?2 yr^?1 for the Masson pine forest (MPF), coniferous and broad‐leaf mixed forest (MF) and subtropical monsoon evergreen broad‐leaf forest (MEBF), respectively, in year 2003/2004, of which 54%, 37% and 62% are belowground NPP for those three respective forests if no change in live plant biomass is assumed. After taking account of the decrease in live plant biomass, we estimated the NPP of the subtropical MEBF is 970 g C m^?2 yr^?1 in year 2003/2004. Total amount of carbon allocated below ground for plant roots is 388 g C m^?2 yr^?1 for the MPF, 504 g C m^?2 yr^?1 for the coniferous and broad‐leaf MF and 1254 g C m^?2 yr^?1 for the subtropical MEBF in 2003/2004. Our results support the hypothesis that the amount of carbon allocation belowground increases during forest succession.     

A Cu‐Based Nanoparticulate Film as Super‐Active and Robust Catalyst Surpasses Pt for Electrochemical H2 Production from Neutral and Weak Acidic Aqueous Solutions

Electrocatalysts that are stable and highly active at low overpotential (η) under mild conditions as well as cost‐effective and scalable are eagerly desired for potential use in photo‐ and electro‐driven hydrogen evolution devices. Here the fabrication and characterization of a super‐active and robust Cu‐Cu_xO‐Pt nanoparticulate electrocatalyst is reported, which displays a small Tafel slope (44 mV dec^?1) and a large exchange current density (1.601 mA cm^?2) in neutral buffer solution. The catalytic current density of this catalyst film reaches 500 mA cm^?2 at η = ?390 ± 12 mV and 20 mA cm^?2 at η = ?45 ± 3 mV, which are significantly higher than the values displayed by Pt foil and Pt/C electrodes in neutral buffer solution and even comparable with the activity of Pt electrode in 0.5 m H₂SO₄ solution.     

GROWTH AND PHOTOSYNTHESIS OF ULVA ROTUNDATA (CHLOROPHYTA) AS A FUNCTION OF TEMPERATURE AND SQUARE WAVE IRRADIANCE IN INDOOR CULTURE1

Temperature and photon flux density (PFD) vary independently in estuaries, e.g. high PFD may occur at any temperature, so it is necessary to consider synergistic effects of these factors on algal growth. Because natural PFD is highly variable and daylength changes confound seasonal temperature cycles, it is easier to interpret factorial experiments in controlled laboratory conditions. Clonal Ulva rotundata Blid. (Chlorophyta) has been studied extensively in outdoor culture. In this study it was maintained indoors under square wave photoperiods at five PFDs and three temperatures. Growth rate, photqsynthetic light response (P-I) curves, and photosystem II chlorophyll fluorescence properties were measured at the growth temperature following acclimation. Interactions between PFD and growth temperature were strongly indicated in all physiological parameters measured. Greatest PFD response occurred at the highest temperature, and the largest temperature response occurred at the highest PFD. Light-saturated photosynthesis (P_m) dark respiration (R_d), and light-limited quantum yield (Φ_m) were sufficient to describe acclimation status. The light-saturation parameter (I_k) was redundant and potentially misleading. Although U. rotundata exhibits a great amplitude of photoacclimation, it apparently has little capacity for temperature acclimation compared to the kelp, Laminaria saccharina, for which published data indicate similar photosynthetic rates over a broad range of growth temperatures. Diurnal variation of P_m and R_d at a growth PFD of ～ 1700 ± 200 μmol photons · m^?2· s^?1 was similar to the pattern observed previously in outdoor culture, suggesting endogenous control of these parameters. Quantum yield and the ratio of variable to maximum chlorophyll fluorescence (F_v/F_m), which were depressed in midday sunlight exceeding ～ 1500 μmol photons · m^?2· s^?1, were relatively invariant through the day in indoor culture, indicating that these parameters are controlled primarily by instantaneous PFD. Growth and fluorescence data are also presented for some other macroalgae for comparative purposes.