Nitrate removal and greenhouse gas production in a stream-bed denitrifying bioreactor

Denitrifying bioreactors are currently being tested as an option for treating nitrate (NO₃^?) contamination in groundwater and surface waters. However, a possible side effect of this technology is the production of greenhouse gases (GHG) including nitrous oxide (N₂O) and methane (CH₄). This study examines NO₃^? removal and GHG production in a stream-bed denitrifying bioreactor currently operating in Southern Ontario, Canada. The reactor contains organic carbon material (pine woodchips) intended to promote denitrification. Over a 1 year period, monthly averaged removal of influent (stream water) NO₃^? ranged from 18 to 100% (0.3–2.5 mg N L^?1). Concomitantly, reactor dissolved N₂O and CH₄ production, averaged 6.4 μg N L^?1 (2.4 mg N m^?2 d^?1), and 974 μg C L^?1 (297 mg C m^?2 d^?1) respectively, where production is calculated as the difference between inflow and effluent concentrations. Gas bubbles entrapped in sediments overlying the reactor had a composition ranging from 19 to 64% CH₄, 1 to 6% CO₂, and 0.5 to 2 ppmv N₂O; however, gas bubble emission rates were not quantified in this study. Dissolved N₂O production rates from the bioreactor were similar to emission rates reported for some agricultural croplands (e.g. 0.1–15 mg N m^?2 d^?1) and remained less than the highest rates observed in some N-polluted streams and rivers (e.g. 110 mg N m^?2 d^?1, Grand R., ON). Dissolved N₂O production represented only a small fraction (0.6%) of the observed NO₃^? removal over the monitoring period. Dissolved CH₄ production during summer months (up to 1236 mg C m^?2 d^?1), was higher than reported for some rivers and reservoirs (e.g. 6–66 mg C m^?2 d^?1) but remained lower than rates reported for some wastewater treatment facilities (e.g. sewage treatment plants and constructed wetlands, 19,500–38,000 mg C m^?2 d^?1).     

Polyvinyl alcohol–silica nanohybrids: An efficient carrier matrix for amylase immobilization

Polyvinyl alcohol (PVA)–silica nanohybrids have been synthesized in a modified Stöber process. The bioactivities of the enzyme loaded hybrids were monitored and the optimum activity sample (H) was calcined at 300 °C in N₂ to obtain hybrid gel (H₃) with improved performance. The synthesized hybrids have been characterized by Fourier Transform Infra Red spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and BET surface area analysis. Under the optimized conditions, the bioactivity of the enzyme impregnated H₃ (H₃-Enz) was 21.823 U/mg. On recycling, H₃-Enz retained 88% of its initial bioactivity in the sixth cycle. The kinetic parameters of soluble starch hydrolysis for the immobilized (K_M = 4.137 mg mL^?1; V_max = 5.95 mg mL^?1 min^?1) and free enzyme (K_M = 10.667 mg mL^?1; V_max = 6.0557 mg mL^?1 min^?1) indicated that the immobilization has nearly doubled the enzyme's affinity for the substrate, while the maximum rate of the enzymatic reaction at the saturation point was not much affected. The immobilized enzyme showed greater shelf life in comparison to the free enzyme.     

Investigation on the formation and kinetics of glucose-fed aerobic granular sludge

Aerobic granular sludge was cultivated in a glass sequencing batch reactor (SBR) with glucose synthetic wastewater. The spherical shaped granules were observed on 4th day with the mean diameter of 0.1 mm. With the increase of chemical oxygen demand (COD) concentration of the influent, aerobic granules grew matured, the size of which ranged from 1.2 to 1.9 mm. The aerobic granular sludge could sustain high organic loading rate (about 4.0 g COD L⁻¹ d⁻¹), with good settling ability (settling velocity 36 m/h) and high biomass concentration (MLSS 6.7 ±0.2 g/L). Experimental data indicated that the substrate utilization and biomass growth kinetics followed Monod's kinetics model approximately. The corresponding kinetic coefficients of maximum specific substrate utilization rate (k), half velocity coefficient (K_s), growth yield coefficient (Y) and decay coefficient (K_d) were 13.2 d⁻¹, 275.8 mg/L, 0.183–0.250 mg MLSS/mg COD and 0.023–0.075 d⁻¹, respectively, which made aerobic granules have short setup period, high rate of substrate utilization and little surplus sludge.     

Silica-supported fluoroboric acid (HBF4–SiO2) catalyzed highly productive synthesis of thiomorpholides as activators of l-asparaginase as well as the antioxidant agent

An efficient solvent-free procedure for the synthesis of thiomorpholides in the presence of a catalytic amount of solid-supported fluoroboric acid (HBF₄–SiO₂) is described. The advantages of this method are high yields, short reaction times, ease of product isolation, low cost, and the catalyst can be recycled for a number of times without significant loss of activity. Three thiomorpholides possessing electron-donating group (4c, 4g, and 4h) were exhibiting excellent stimulatory activities against Erwinia carotovora l-asparaginase. The most potent activator, compound 4h displayed the following kinetic parameters, K_m = 75 μM and V_max = 1000 μmol mg^?1 min^?1 and K_A = 0.985 μM. Furthermore, these compounds (4g, 4h, 4c, 4f, 4a, and 4d) have also shown promising 2,2′-diphenyl-1-picrylhydrazyl (DPPH) reducing antioxidant activity (21–36%) at 1 mM concentration as compared to standard butylated hydroxyl anisole (72% at 1 mM).     

Nitrate removal processes in a constructed wetland treating drainage from dairy pasture

¹⁵N-labelled NO₃^? was used in a surface-flow constructed wetland in spring to examine the relative importance of competing NO₃^? removal processes. In situ mesocosms (0.25 m²) were dosed with 2 l of ¹⁵NO₃^? (NaNO₃, 300 mg N l^?1, 99 atom% ¹⁵N) and bromide (Br^?) solution (LiBr, 4.3 g l^?1, as a conservative tracer). Concentrations of NO₃^?, Br^?, dissolved oxygen and ¹⁵N₂ were monitored periodically and replicate mesocosms were destructively sampled prior to and 6 days after ¹⁵N addition. Denitrification, immobilisation, plant uptake and dissimilatory NO₃^? reduction to NH₄⁺ (DNRA) accounted for 77, 11, 9 and 2% of ¹⁵NO₃^? transformed during the experiment. Only 6% of denitrification gases were directly measured as atmospheric or dissolved ¹⁵N₂; the remainder (71%) was determined via ¹⁵N mass balance. This indicated that a large proportion of the denitrification gases were entrapped within the soil matrix and/or plant aerenchyma. The floating plant Lemna minor exhibited a significantly higher NO₃^? uptake rate (221 mg kg^?1 d^?1) than Typha orientalis (10 mg kg^?1 d^?1), but periodic harvest of plants would remove <3% of annual NO₃^? inputs. Our results suggest that this 6-year-old constructed wetland functions effectively as a sink for NO₃^? during the growing season with less than one-quarter of the NO₃^? processed sequestered into wetland plant, algal and microbial N pools and the balance permanently removed by denitrification.     

Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg^?1 Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg^?1 (57.1%) at the rate of 3.97 × 10^?10 mg kg^?1 cell^?1 day^?1 Tapis blended crude oil from 1000 mg kg^?1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg^?1 (63.0%) Tapis blended crude oil from the 1000 mg kg^?1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10^?10 mg kg^?1 cell^?1 day^?1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C₁₂–C₃₄) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.     

Characterization of a HAP–phytase from a thermophilic mould Sporotrichum thermophile

The phytase of Sporotrichum thermophile was purified to homogeneity using acetone precipitation followed by ion-exchange and gel-filtration column chromatography. The purified phytase is a homopentamer with a molecular mass of ～456 kDa and pI of 4.9. It is a glycoprotein with about 14% carbohydrate, and optimally active at pH 5.0 and 60 °C with a T_1/2 of 16 h at 60 °C and 1.5 h at 80 °C. The activation energy of the enzyme reaction is 48.6 KJ mol^?1 with a temperature quotient of 1.66, and it displayed broad substrate specificity. Mg²⁺ exhibited a slight stimulatory effect on the enzyme activity, while it was markedly inhibited by 2,3-butanedione suggesting a possible role of arginine in its catalysis. The chaotropic agents such as guanidinium hydrochloride, urea and potassium iodide strongly inhibited phytase activity. Inorganic phosphate inhibited enzyme activity beyond 3 mM. The maximum hydrolysis rate (V_max) and apparent Michaelis–Menten constant (K_m) for sodium phytate were 83 nmol mg^?1 s^?1 and 0.156 mM, respectively. The catalytic turnover number (K_cat) and catalytic efficiency (K_cat/K_m) of phytase were 37.8 s^?1 and 2.4 × 10⁵ M^?1 s^?1, respectively. Based on the N-terminal and MALDI–LC–MS/MS identified amino acid sequences of the peptides, the enzyme did not show a significant homology with the known phytases.     

CBOD5 treatment using the marshland upwelling system

Five-day carbonaceous biochemical oxygen demand (CBOD₅) removal efficiency was evaluated for the marshland upwelling system (MUS) under both intermediate and saltwater conditions. The MUS treated decentralized wastewater from two private camps and a public restroom in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi, and one private camp in the Barataria Terrebonne National Estuary, along Bayou Segnette, Louisiana. Raw wastewater was injected into the surrounding subsurface at a depth of 3.8 or 4.3 m. Various injection flow rates and frequencies were tested in addition to a synthetic wastewater trial. All trials followed a first-order background corrected removal equation, resulting in removal constants ranging from 0.49 to 3.32 m^?1 and predicted surface concentrations from 5.7 to 33.0 mg L^?1. CBOD₅ (unfiltered) influent concentrations of 282 ± 173 mg L^?1 were reduced to an overall effluent mean of 13 ± 13 mg L^?1 by a vector distance of 7 m at Moss Point and from 365 ± 151 mg L^?1 to 3.6 ± 7.6 mg L^?1 by a vector distance of 6 m for Bayou Segnette. Of seven trials, only one failed to achieve effluent CBOD₅ levels below a National Pollutant Discharge Elimination System (NPDES) standard level of 25 mg L^?1.     

Metabolic,hygric and ventilatory physiology of the red-tailed phascogale (Phascogale calura; Marsupialia,Dasyuridae): Adaptations to aridity or arboreality?

The red-tailed phascogale is a small arboreal dasyurid marsupial that inhabits semi-arid to arid regions of Western Australia's wheat belt. Its body mass (34.7 g) is only ～15% of that predicted based on its phylogenetic position among other dasyuromorphs; we interpret this as an adaptation to its scansorial and semi-arid/arid lifestyle. The standard physiology of this species at a thermoneutral ambient temperature of 30 °C conforms to that of other dasyurid marsupials; body temperature (34.7 ± 0.37 °C), basal metabolic rate (0.83 ± 0.076 mL O₂ g^?1 h^?1), evaporative water loss (1.68 ± 0.218 mg H₂O g^?1 h^?1) and wet thermal conductance (3.8 ± 0.26 J g^?1 h^?1 °C^?1) all fall within the 95% predication limits for the respective allometric relationships for other dasyurid species. Thermolability confers an energy savings at low T_a and water savings at high T_a. Torpor, observed at low T_a, was found to be more beneficial for energy savings than for water economy. The red-tailed phascogale therefore has a physiology suitable for the challenges of arid environments without any obvious requirement for adaptations to its scansorial lifestyle, other than its considerably lower-than-expected body mass.     

Modulation of guanosine 5′-diphosphate-d-mannose metabolism in recombinant Escherichia coli for production of guanosine 5′-diphosphate-l-fucose

Guanosine 5’-diphosphate (GDP)-l-fucose, an activated form of a nucleotide sugar, plays an important role in a wide range of biological functions. In this study, the enhancement of GDP-l-fucose production was attempted by supplementation of mannose, which is a potentially better carbon source to be converted into GDP-l-fucose than glucose, and combinatorial overexpression of the genes involved in the biosynthesis of GDP-d-mannose, a precursor of GDP-l-fucose. Supply of a mannose and glucose led to a 1.3-fold-increase in GDP-l-fucose concentration (52.5 ± 0.8 mg l^?1) in a fed-batch fermentation of recombinant E. coli BL21star(DE3) overexpressing the gmd and wcaG genes, compared with the case using glucose as a sole carbon source. A maximum GDP-l-fucose concentration of 170.3 ± 2.3 mg l^?1, corresponding to a 4.4-fold enhancement compared with the control strain overexpressing gmd and wcaG genes only, was achieved in a glucose-limited fed-batch fermentation of a recombinant E. coli BL21star(DE3) strain overexpressing manB, manC, gmd and wcaG genes. Further improvement of GDP-l-fucose production was not obtained by additional overexpression of the manA gene.     

Does UV-B influence biomass growth in lichens deficient in sun-screening pigments?

This study aimed to assess biomass growth as a response variable in lichens during short-term laboratory experiments. To do this, we studied the influence of UV-B and temperature on lichen performance including the synthesis of solar radiation screening cortical compounds. The pioneer lichen Xanthoria aureola from exposed sea cliffs and the old forest lichen Lobaria pulmonaria were cultivated for 15 days in the laboratory in a factorial experiments with temperature (12 and 21 °C) and UV-B (0, 0.1, 0.3 and 1.0 W m^?2) as treatments. Prior to the experiment, the cortical pigment parietin was non-destructively extracted from X. aureola, whereas the sampled shade-adapted thalli of L. pulmonaria lacked cortical melanic compounds. Therefore both lichens were deficient in cortical sun-screening compounds when the UV-B exposure started. At 12 °C, the relative growth rate was 7.2 ± 0.6 and 3.0 ± 0.8 mg g^?1 day^?1 in L. pulmonaria and X. aureola, respectively, reduced to 1.8 ± 0.5 and ?2.6 ± 0.9 mg g^?1 day^?1, at 21 °C. These figures showed that lichen growth is a useful response variable in short-term laboratory experiments. Growth was not influenced by UV-B alone in these pigment-deficient transplants, suggesting that UV-B had little adverse effects on either of the lichen bionts. The cortical sun screens (parietin and melanic compounds) were synthesized in the presence of UV-B, and increased statistically significantly with increasing UV-B at both cultivation temperatures. However, in X. aureola the synthesis was highest at the lowest temperature (12 °C). At 12 °C, changes in chlorophylls, F_v/F_m and NPQ during cultivation were consistent with a substantial level of acclimation to the growth chamber conditions for both species, whereas strong reductions in photosynthetic pigments, F_v/F_m and Ф_II at 21 °C indicated serious damage and chlorophyll degradation at high temperature. In conclusion, lichen growth and the synthesis of protective compounds are highly responsive lichen processes in short-term experiments.     

Purification and characterization of a new laccase from Shiraia sp.SUPER-H168

A new laccase from Shiraia sp.SUPER-H168 was purified by ion exchange column chromatography and gel permeation chromatography and the apparent molecular mass of this enzyme was 70.78 kDa, as determined by MALDI/TOF-MS. The optimum pH value of the purified laccase was 4, 6, 5.5 and 3 with 2,6-dimethoxyphenol (DMP), syringaldazine, guaiacol and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) as substrates, respectively. The optimum temperature of the purified laccase was 50 °C using DMP, syringaldazine and guaiacol as substrates, but 60 °C for ABTS. Inhibitors and metal ions of SDS, NaN₃, Ag⁺ and Fe³⁺ showed inhibition on enzyme activity of 10.22%, 7.86%, 8.13% and 67.50%, respectively. Fe²⁺ completely inhibited the purified laccase. The K_cat/K_m values of the purified laccase toward DMP, ABTS guaiacol and syringaldazine were 3.99 × 10⁶, 3.74 × 10⁷, 8.01 × 10⁴ and 2.35 × 10⁷ mol^?1 L S^?1, respectively. The N-terminal amino acid sequence of the purified laccase showed 36.4% similarity to Pleurotus ostrestus. Approximately 66% of the Acid Blue 129 (100 mg L^?1) was decolorized by 2.5 U of the purified laccase after a 120 min incubation at 50 °C. Acid Red 1 (20 mg L^?1) and Reactive Black 5 (50 mg L^?1) were decolorized by the purified laccase after the addition of Acid Blue 129 (100 mg L^?1).     

Optimisation and scale-up of α-glucuronidase production by recombinant Saccharomyces cerevisiae in aerobic fed-batch culture with constant growth rate

α-Glucuronidase (EC 3.2.1.139) of family GH 115 from Scheffersomyces stipitis is a valuable enzyme for the modification of water-soluble xylan into insoluble biopolymers, due to its unique ability to act on polymeric xylans. The influence of growth rate on the production of α-glucuronidase by recombinant Saccharomyces cerevisiae MH1000pbk10D-glu in glucose-limited fed-batch culture was studied at 14 and 100 L scale. At and below the critical specific growth rate (μ_crit) of 0.12 h⁻¹ at 14 L scale, the biomass yield coefficient (Y_x/s) remained constant at 0.4 g g⁻¹ with no ethanol production, whereas ethanol yields relative to biomass (k_eth/x) of up to 0.54 g g⁻¹ and a steady decrease in Y_x/s were observed at μ > 0.12 h⁻¹. Production of α-glucuronidase was growth associated at a product yield (k_α-glu/x) of 0.45 mg g⁻¹, with the highest biomass (37.35 g/L) and α-glucuronidase (14.03 mg/L) concentrations, were recorded during fed-batch culture at or near to μ_crit. Scale-up with constant k_La from 14 to 100 L resulted in ethanol concentrations of up to 2.5 g/L at μ = 0.12 h⁻¹. At this scale, α-glucuronidase yield could be maximised at growth rates below μ_crit, to prevent localised high glucose concentration pockets at the feed entry zone that would induce oxido-reductive metabolism. This is the first report where recombinant production of α-glucuronidase (EC 3.2.1.139) by S. cerevisiae was optimised for application at pilot scale.     

Design and synthesis of a β-lactamase activated 5-fluorouracil prodrug

An efficient synthesis of a 5-fluorouracil-cephalosporin prodrug is described for use against colorectal and other cancers in antibody and gene-directed therapies. The compound shows stability in aqueous media until specifically activated by β-lactamase (βL). The kinetic parameters of the 5-fluorouracil-cephalosporin conjugate were determined in the presence of Enterobacter cloacae P99 βL (ECl βL) revealing a K_m = 95.4 μM and V_max = 3.21 μMol min^?1 mg^?1. The data compare favorably to related systems that have been reported and enable testing of this prodrug against cancer cell lines in vitro and in vivo.     

Synthesis of thermo-sensitive copolymer with affinity butyl ligand and its application in lipase purification

In this study, thermo-sensitive N-alkyl substituted polyacrylamide polymer P_NNB was synthesized by using N-hydroxymethyl acrylamide(NHAM), N-isopropyl acrylamide (NIPA) and butyl acrylate (BA) as monomers, and its low critical solution temperature (LCST) was controlled to be 28 °C. The recovery of the thermo-sensitive polymer was over 98%. Butanol as a hydrophobic ligand was covalently attached onto polymer P_NNB and butyl ligand density was 80 μmol g^?1 polymer. The affinity polymer was used for purification of lipase from crude material. Optimized condition was pH 7.0, 35 °C adsorption temperature, 120 min adsorption time and 0.5 mg ml^?1 initial concentration of lipase. The adsorption isotherm accords with a typical Langmuir isotherm. The maximum adsorption capacity (Q_m) of the affinity polymer for lipase was 24.8 mg g^?1polymer. The affinity copolymer could be recycled by temperature-inducing precipitation and there was only about 6% loss of adsorption capacity after five recyclings. Specific activity of lipase was improved from 14 IU mg^?1 to 506 IU mg^?1 protein, and its recovery achieved 82%. The affinity polymer is suitable for the purification of target proteins from the crude material with large volume and dilute solution.     

Investigation on the properties and kinetics of glucose-fed aerobic granular sludge

Aerobic granulation is a process in which suspended biomass aggregate and form discrete well-defined granules in aerobic systems. To investigate the properties and kinetics of aerobic granular sludge, aerobic granules were cultivated with glucose synthetic wastewater in a series of sequencing batch reactors (SBR). The spherical shaped granules were observed on 8th day with the mean diameter of 0.1 mm. With the organic loading rate (OLR) being increased to 4.0 g COD L⁻¹ d⁻¹, aerobic granules grew matured with spherical shape. The size of granules ranged from 1.2 to 1.8 mm, and the corresponding settling velocity of individual granule was 24.2–36.4 m h⁻¹. The oxygen utilization rate (OUR) of mature granules was 41.90 g O₂ kg MLSS⁻¹ h⁻¹, which was two times higher than that of activated sludge (18.32 g O₂ kg MLSS⁻¹ h⁻¹). The experimental data indicated that the substrate utilization and biomass growth kinetics generally followed Monod's kinetics model. The corresponding kinetic coefficients of k (maximum specific substrate utilization rate), K_s (half velocity coefficient), Y (growth yield coefficient) and K_d (decay coefficient) were determined as follows, k_c = 23.65 d⁻¹, K_c = 3367.05 mg L⁻¹, K_N = 0.038 d⁻¹, K_N = 29.65 mg L⁻¹, Y = 0.1927–0.2022 mg MMLS (mg COD)⁻¹ and K_d = 0.00845–0.0135 d⁻¹, respectively. Those properties of aerobic granules made aerobic granules system had a short setup period, high substrate utilization rate and low sludge production.     

Cytogenetic,cross-mating and molecular evidence of four cytological races of Anopheles crawfordi (Diptera: Culicidae) in Thailand and Cambodia

Twenty-nine isolines of Anopheles crawfordi were established from wild-caught females collected from cow-baited traps in Thailand and Cambodia. Three types of X (X₁, X₂, X₃) and four types of Y (Y₁, Y₂, Y₃, and Y₄) chromosomes were identified, according to differing amounts of extra heterochromatin. These sex chromosomes represent four metaphase karyotypes, i.e., Forms A (X₁, X₂, X₃, Y₁), B (X₁, X₂, X₃, Y₂), C (X₂, Y₃) and D (X₂, Y₄). Forms C and D are novel metaphase karyotypes confined to Thailand, whereas forms A and B appear to be common in both Thailand and Cambodia. Cross-mating experiments between the four karyotypic forms indicated genetic compatibility in yielding viable progenies and synaptic salivary gland polytene chromosomes. The results suggest that the forms are conspecific and A. crawfordi comprises four cytological races, which is further supported by very low intraspecific variation (mean genetic distance = 0.000–0.018) of the nucleotide sequences in ribosomal DNA (ITS2) and mitochondrial DNA sequences (COI, COII).     

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.     

Beef cattle pasture to wetland reconversion: Impact on soil organic carbon and phosphorus dynamics

There is a major need to understand the historical condition and chemical/biological functions of the ecosystems following a conversion of wetlands to agricultural functions. To better understand the dynamics of soil total organic carbon (TOC) and phosphorus (P) during beef cattle pastures to wetland reconversion, soil core samples were collected from the beef cattle pasture and from the natural wetland at Plant City, FL, during five summer seasons (2002–2007). The levels of TOC and soil P were significantly affected by changing land use and hydrology. Draining natural wetlands to grazed pastures resulted in very pronounced reduction of TOC from 180.1 to 5.4 g g^?1. Cumulative concentrations of total phosphorus (TP) in soils (1134 mg kg^?1) under drained condition are two to three times lower than those in soils (2752 mg kg^?1) under flooded condition over the periods of land use reconversion. There was a declining trend (r = 0.82**; p ≤ 0.01) in total soil P from natural wetland (763 mg kg^?1) to altered pastures (340 mg kg^?1), largely as organic-bound P (natural wetland, 48%; grazed pastures, 44%; altered pastures, 29%). These results are important in establishing baseline information on soil properties in pasture and wetland prior to restoring and reconverting pasture back to wetland conditions. The results further suggest that changes in soil properties due to changing land use and hydrologic conditions (drying and re-wetting) could be long lasting.