Mathematical description of bikaverin production in a fluidized bed bioreactor

Summary  Growth of Gibberella fujikuroi in submerged cultures occurs as micelles or filamentous hyphae dispersed in fluid and pellets or stable, spherical agglomerations. Gibberella fujikuroi growth, substrate consumption and bikaverin production kinetics obtained from submerged batch fermentation were fitted to three different sigmoid models: two and three-parameter Gompertz models and one Logistic model. Growth fitting was used to compare between models and select the best one by means of an F test. The best model for describing growth was the two-parameter Gompertz model and was used for glucose consumption and bikaverin production fitting. Data from eight different schemes of fermentations were analysed and parameter estimation was carried out by means of minimization of residual sum of squares. Some characteristic values obtained with the two-parameter Gompertz model fit are: μ=0.028 h⁻¹, Y_x/s=0.1089 g substrate/g biomass, α =0.1384 g product/g biomass.     

Specific growth rate as a determinant of the carbon isotope composition of the temperate seagrass Zostera marina

The seasonal variability of specific growth rate and the carbon stable isotope ratio (δ¹³C) of leaf blades (δ¹³C_leaf) of a temperate seagrass, Zostera marina (within 10 days old) were measured simultaneously, together with the δ¹³C of dissolved inorganic carbon (δ¹³C_DIC) at three sites in the semi-closed Akkeshi estuary system, northeastern Japan, in June, September, and November 2004. The δ¹³C_leaf ranged from −16.2 to −6.3‰ and decreased from summer to winter. The simultaneous measurement of the δ¹³C_leaf, growth rate, and morphological parameters (mean leaf length and width, mean number of leaves per shoot, and sheath length) of the seagrass and δ¹³C_DIC in the surrounding water allowed us to compare directly the δ¹³C_leaf and specific growth rate of seagrass. The difference in the δ¹³C of seagrass leaves relative to the source DIC (Δδ¹³C_{leaf − DIC}) was the least negative (−11 to −7‰) in June at all three sites and became more negative (−17 to −8‰) as the specific growth rate decreased. This positive correlation between Δδ¹³C_{leaf − DIC} and specific growth rate can be used to diagnose the growth of seagrasses. Δδ¹³C_{leaf − DIC} changed by −1.7 ± 0.2‰ when the leaf specific growth rate decreased by 1% d⁻¹.     

Quantification of hydrogen peroxide and glucose using 3-methyl-2-benzothiazolinonehydrazone hydrochloride with 10,11-dihydro-5H-benz(b,f)azepine as chromogenic probe

A sensitive, selective, and rapid enzymatic method is proposed for the quantification of hydrogen peroxide (H₂O₂) using 3-methyl-2-benzothiazolinonehydrazone hydrochloride (MBTH) and 10,11-dihydro-5H-benz(b,f)azepine (DBZ) as chromogenic cosubstrates catalyzed by horseradish peroxidase (HRP) enzyme. MBTH traps free radical released during oxidation of H₂O₂ by HRP and gets oxidized to electrophilic cation, which couples with DBZ to give an intense blue-colored product with maximum absorbance at 620 nm. The linear response for H₂O₂ is found between 5 × 10⁻⁶ and 45 × 10⁻⁶ mol L⁻¹ at pH 4.0 and a temperature of 25 °C. Catalytic efficiency and catalytic power of the commercial peroxidase were found to be 0.415 × 10⁶ M⁻¹ min⁻¹ and 9.81 × 10⁻⁴ min⁻¹, respectively. The catalytic constant (k_cat) and specificity constant (k_cat/K_m) at saturated concentration of the cosubstrates were 163.2 min⁻¹ and 4.156 × 10⁶ L mol⁻¹ min⁻¹, respectively. This method can be incorporated into biochemical analysis where H₂O₂ undergoes catalytic oxidation by oxidase. Its applicability in the biological samples was tested for glucose quantification in human serum.     

Isolation of cellulose-hydrolytic bacteria and applications of the cellulolytic enzymes for cellulosic biohydrogen production

Nine cellulolytic bacterial strains were isolated from soil sample taken in southern Taiwan. Through 16S rRNA sequence matching; eight of those isolates belong to Cellulomonas sp., while the other one belongs to Cellulosimicrobium cellulans. The activity of cellulolytic enzymes (cellulases and xylanase) produced from those strains was mainly present extracellularly and the enzyme production was dependent on cellulosic substrates (xylan, rice husk and rice straw) used for growth. HPLC analysis confirmed the bacterial hydrolysis of these cellulosic substrates for soluble sugars production. The efficiency of fermentative H₂ production from the enzymatically hydrolyzed rice husk was examined with seven H₂-producing pure bacterial isolates. With an initial reducing sugar concentration of 0.36 g l⁻¹, only Clostridium butyricum CGS5 exhibited efficient H₂ production from the rice husk hydrolysates with a cumulative H₂ production and H₂ yield of 88.1 ml l⁻¹ and 19.15 mmol H₂ (g reducing sugar)⁻¹ (or 17.24 mmol H₂ (g cellulose)⁻¹), respectively.     

Nitrogen utilization by the raphidophyte Heterosigma akashiwo: Growth and uptake kinetics in laboratory cultures

The nitrogen uptake and growth capabilities of the potentially harmful, raphidophycean flagellate Heterosigma akashiwo (Hada) Sournia were examined in unialgal batch cultures (strain CCMP 1912). Growth rates as a function of three nitrogen substrates (ammonium, nitrate and urea) were determined at saturating and sub-saturating photosynthetic photon flux densities (PPFDs). At saturating PPFD (110 μE m⁻² s⁻¹), the growth rate of H. akashiwo was slightly greater for cells grown on NH₄⁺ (0.89 d⁻¹) compared to cells grown on NO₃⁻ or urea, which had identical growth rates (0.82 d⁻¹). At sub-saturating PPFD (40 μE m⁻² s⁻¹), both urea- and NH₄⁺-grown cells grew faster than NO₃⁻-grown cells (0.61, 0.57 and 0.46 d⁻¹, respectively). The N uptake kinetic parameters were investigated using exponentially growing batch cultures of H. akashiwo and the ¹⁵N-tracer technique. Maximum specific uptake rates (V_max) for unialgal cultures grown at 15 °C and saturating PPFD (110 μE m⁻² s⁻¹) were 28.0, 18.0 and 2.89 × 10⁻³ h⁻¹ for NH₄⁺, NO₃⁻ and urea, respectively. The traditional measure of nutrient affinity—the half saturation constants (K_s) were similar for NH₄⁺ and NO₃⁻ (1.44 and 1.47 μg-at N L⁻¹), but substantially lower for urea (0.42 μg-at N L⁻¹). Whereas the α parameter (α = V_max/K_s), which is considered a more robust indicator for substrate affinity when substrate concentrations are low (<K_s), were 19.4, 12.2 and 6.88 × 10⁻³ h⁻¹/(μg-at N L⁻¹) for NH₄⁺, NO₃⁻ and urea, respectively. These laboratory results demonstrate that at both saturating and sub-saturating N concentrations, N uptake preference follows the order: NH₄⁺ > NO₃⁻ > urea, and suggests that natural blooms of H. akashiwo may be initiated or maintained by any of the three nitrogen substrates examined.     

Annual cycle of CO2 exchange over a reed (Phragmites australis) wetland in Northeast China

Net ecosystem exchange of CO₂ (NEE) was measured during 2005 using the eddy covariance (EC) technique over a reed (Phragmites australis (Cav.) Trin. ex Steud.) wetland in Northeast China (121°54′E, 41°08′N). Diurnal NEE patterns varied markedly among months. Outside the growing season, NEE lacked a diurnal pattern and it fluctuated above zero with an average value of 0.07 mg CO₂ m⁻² s⁻¹ resulting from soil microbial activity. During the growing season, NEE showed a distinct V-like diel course, and the mean daily NEE was −7.48 ± 2.74 g CO₂ m⁻² day⁻¹, ranging from −13.58 g CO₂ m⁻² day⁻¹ (July) to −0.10 g CO₂ m⁻² day⁻¹ (October). An annual cycle was also apparent, with CO₂ uptake increasing rapidly in May, peaking in July, and decreasing from August. Monthly cumulative NEE ranged from −115 ± 24 g C m⁻² month⁻¹ (the reed wetland was a CO₂ sink) in July to 75 ± 16 g C m⁻² month⁻¹ (CO₂ source) in November. The annual CO₂ balance suggests a net uptake of −65 ± 14 g C m⁻² year⁻¹, mainly due to the gains in June and July. Cumulative CO₂ emission during the non-growing season was 327 g C m⁻², much greater than the absolute value of the annual CO₂ balance, which proves the importance of the wintertime CO₂ efflux at the study site. The ratio of ecosystem respiration (R_eco) to gross primary productivity (GPP) for this reed ecosystem was 0.95, indicating that 95% of plant assimilation was consumed by the reed plant or supported the activities of heterotrophs in the soil. Daytime NEE values during the growing season were closely related to photosynthetically active radiation (PAR) (r² > 0.63, p < 0.01). Both maximum ecosystem photosynthesis rate (A_max) and apparent quantum yield (α) were season-dependent, and reached their peak values in July (1.28 ± 0.11 mg CO₂ m⁻² s⁻¹, 0.098 ± 0.027 μmol CO₂ μmol⁻¹ photon, respectively), corresponding to the observed maximum NEE in July. Ecosystem respiration (R_eco) relied on temperature and soil water content, and the mean value of Q₁₀ was about 2.4 with monthly variation ranging from 1.8 to 4.1 during 2005. Annual methane emission from this reed ecosystem was estimated to be about 3 g C m⁻² year⁻¹, and about 5% of the net carbon fixed by the reed wetland was released to the atmosphere as CH₄.     

Synthesis, characterization and aqueous dispersion of dextran-g-poly(1,4-dioxan-2-one) copolymers

A novel biodegradable graft copolymer, dextran-g-poly(1,4-dioxan-2-one) (PODEX), was synthesized through the ring-opening polymerization (ROP) of 1,4-dioxan-2-one (PDO) onto a dextran backbone. Initially, dextran was silylated with 1,1,1,3,3,3-hexamethyldisilazane. The grafting from pathway was conducted with various (30–70) PDO/OH feed ratios to obtain PODEX copolymers with a various PPDO graft structures. Graft copolymers were characterized by FT-IR, ¹H and ¹³C NMR, DSC, TGA, and WAXD. Molecular weights of the PODEX copolymers (M_W: 94,700–117, 300 Da), glass transition temperature (−29 to −17 °C), melting temperature (82–100 °C), and crystallinity (32–40%) were increased with the content of PPDO. AFM observations revealed that polymeric micelles were spherical and uniform in morphology with around 30–58 nm diameter. Critical micelle concentration (CMC) of self-assembled system was significantly decreased from 3.2 to 1.09 mg/L with the increment of PPDO.     

Influence of humic, fulvic and hydrophilic acids on the growth, photosynthesis and respiration of the dinoflagellate Prorocentrum minimum (Pavillard) Schiller

Blooms of the dinoflagellate Prorocentrum minimum often occur in coastal regions characterized by variable salinity and elevated concentrations of terrestrially derived dissolved organic carbon (DOC). Humic, fulvic and hydrophilic acid fractions of DOC were isolated from runoff entering lower Narragansett Bay immediately after a rainfall event and the influence of these fractions upon P. minimum growth, cell yield, photosynthesis and respiration was examined. All organic fractions stimulated growth rates and cell yields compared with controls (no organic additions), but the extent of stimulation varied with the fraction and its molecular weight. Greatest stimulations were observed with humic and fulvic acids additions; cell yields were more than 2.5 and 3.5 times higher than with hydrophilic acid additions while growth rates were 21 and 44% higher, respectively. Responses to additions of different molecular weight fractions of each DOC fraction suggest that growth rate effects were attributable to specific molecular weight fractions: the >10,000 fraction of humic acids, both the >10,000 and <500 fractions of fulvic acids and the <10,000 fraction of hydrophilic acids. The form and concentration of nitrogen (as NO₃⁻ or NH₄⁺) present also influenced P. minimum response to DOC; 10–20 μg ml⁻¹ additions of fulvic acid had no effect upon growth rates in the presence of NH₄⁺ but significantly increased growth rates in the presence of NO₃⁻, a relationship probably related to fulvic acid effects upon trace metal bioavailability and subsequent regulation of the biosynthesis of enzymes required for NO₃⁻ assimilation. The influence of DOC additions on P. minimum respiration and production rates also varied with the organic fraction and its concentration. Production rates ranged from 1.1 to 3.4 pg O₂ cell⁻¹ h⁻¹, with highest rates observed upon exposure to fulvic and hydrophilic acid concentrations of >10 μm ml⁻¹. Low concentrations (5–10 μg ml⁻¹) of humic acid had no statistically significant effect upon production, but exposure to concentrations >25 μg ml⁻¹ resulted in a 30% decrease in O₂ evolution, probably due to light attenuation by the highly colored humic acid fraction. Respiration rates ranged from 1.2 to 2.7 pg O₂ cell⁻¹ h⁻¹ and were elevated upon exposure to both fulvic and hydrophilic acids, but not to humic acid. These results demonstrate that terrestrially derived DOC fractions play an active role in stimulation of P. minimum growth via direct effects upon growth, yield and photosynthesis as well as via indirect influences such as interactions with nitrogen and effects upon light attenuation.     

Predictive model for growth of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> in untreated and treated lettuce with alkaline electrolyzed water

This study was performed to develop predictive models for the growth kinetics of Listeria monocytogenes in Ready-to-Eat (RTE) lettuce treated with or without alkaline electrolyzed water. Firstly, growth curves of L. monocytogenes in treated and untreated RTE lettuce were obtained at several isothermal conditions (4, 10, 15, 20, 25, 30, and 35°C) and were then fitted into Gompertz model with a high correlation coefficient (R ² > 0.99). Growth parameters such as growth rate (GR) and lag time (LT) estimated by Gompertz model were found mostly have significant difference (P < 0.05) with those predicted by Combined database for predictive microbiology (ComBase). Moreover, increased GR and decreased LT were observed with increasing storage temperatures from 4 to 35°C and untreated lettuce showed lowest GR or longest LT, and followed by treated lettuce and ComBase, respectively. Furthermore, square root equation was employed to establish the secondary models for the GR to evaluate the effect of different storage temperatures on the growth rate of L. monocytogenes in untreated lettuce and treated lettuce. After that, verification of the developed models has been carried out using several mathematical or statistical indicators such as R ², the average mean square error (MSE), bias factor (B _f) and accuracy factor (A _f). It showed that R ² values were close to 1 (>0.95), and MSE calculated from models of untreated and treated lettuce were 0.0011 and 0.0008, respectively. Also, B _f values of 0.980 and 1.034 and A _f values of 1.107 and 1.118 were all in the acceptable range. This demonstrated that overall predictions showed good agreement with the experimental values, indicating success at providing reliable predictions of L. monocytogenes growth in RTE lettuce.     

Effect of conjugated linoleic acid on dietary lipids utilization, liver morphology and selected immune parameters in sea bass juveniles (Dicentrarchus labrax)

Increased energy content in fish feeds has led to an enhanced fat deposition, particularly in European sea bass, concerning fish farmers. Inclusion of conjugated linoleic acid (CLA) could reduce fat deposition as in other vertebrates. To determine if dietary CLA affects fat deposition, lipid metabolism, lipid composition and morphology of different tissues, growth and selected immune parameters, European sea bass juveniles were fed 4 graded levels of CLA (0, 0.5, 1 and 2%). Growth and feed conversion were not affected by CLA, whereas feed intake was reduced (P < 0.05) by feeding 2% CLA. In these fish perivisceral fat was also reduced (P < 0.05), particularly reducing (P < 0.05) monounsaturated fatty acids. CLA has not affected tissue proximal composition, but reduced (P < 0.05) saturated and monounsaturated fatty acids and increased (P < 0.05) the n−3 and n−3 highly unsaturated fatty acids in muscle and increase (P < 0.05) CLA content in muscle, liver and perivisceral fat. A progressive reduction in lipid vacuolization of hepatocytes cytoplasm and regular-shaped morphology was found in fish fed increased CLA levels, together with a progressive increase in malic enzyme activity (only significant in fish fed 1% CLA). Finally, inclusion of CLA up to 1% increased (P < 0.05) plasma lysozyme activity and was positively correlated with alternative complement pathway.     

Representing Cumulative Germination.: 2. The Use of the Weibull Function and Other Empirically Derived Curves

The Weibull, Morgan–Mercer–Flodin, Richards, Mitscherlich,Gompertz and logistic functions were each fitted to a wide rangeof cumulative germinations of non-dormant seed. The Weibullproved the most suitable for describing cumulative germinationas it provided a consistently close fit to the data and wasinsensitive to choice of starting values, thus making it fairlyeasy to fit. The others provided either an inferior fit or elsea similar fit but with a greater sensitivity to starting values. The four parameters of the Weibull function reflect maximumgermination, germination rate, the lag in the onset of germinationand the shape of the cumulative distribution. A comparison between non-linear and linear fits of the Mitscherlich,Gompertz and logistic functions showed the clear superiorityof non-linear methods. Cumulative germination, Weibull function, Richards function, Morgan–Mercer–Flodin function, Mitscherlich (monomolecular) function, Gompertz function, logistic (autocatalytic) function, modelling, simulation     

The potential of Commelina benghalensis as a forage for ruminants

To evaluate the potential of Commelina benghalensis as a forage for ruminants, effects of plant maturity on chemical composition, rumen degradability as well as its increased dietary inclusion level on intake, digestibility and N balance in sheep fed Sorghum almum were investigated with forage obtained from the wild, re-established and harvested at 6, 10 and 14 weeks of growth. Composite herbage samples were analyzed for dry matter (DM), chemical components, total extractable phenolics (TEP) and amino acid content. In sacco rumen degradability measurements used six individually confined wethers (8 ± 0.5 months of age; 21 ± 2.6 kg live-weight (LW)) fitted with rumen cannulae and fed a ration of 3:1 fresh S. almum and Medicago sativa hay (about 1:2 on a DM basis). In sacco bags containing 5 g each of dry herbage were inserted into the rumen and withdrawn sequentially after 0, 12, 24, 36 and 48 h. Metabolizable energy (ME) was estimated from 24 h in vitro gas production. In the digestibility study, 12 wethers fitted with rumen canula were housed in metabolic crates and allotted to four treatment diets (i. e., D0, D10, D20 and D30) constituted from fresh S. almum and pre-wilted C. benghalensis in a randomized complete block design. The control diet (D0) was 3 kg fresh S. almum (≈535.5 g DM/wether/d about 30 g/kg LW), whereas D10, D20 and D30 were D0 +300, 600 or 900 g of wilted C. benghalensis (≈34, 68 or about 102 g DM/wether/d), respectively. The study lasted for 21 d. Dry matter, fibre and TEP content increased (P<0.001) with maturity of the forage, whereas those of CP and EE decreased (P<0.0001) over the same period. Amino acids (AA) also declined with maturity (P<0.05). Rumen degradability of DM and OM were unaffected, but DM intake increased linearly (P<0.0001) at a decreasing rate (Q: P<0.05) and DM digestibility (DMD) and N intake increased linearly (P<0.01 and P<0.0001, respectively) as level of C. benghalensis in the diet increased. Results indicate that advancing maturity affected chemical composition, but not rumen degradability, of C. benghalensis and also demonstrated that inclusion of C. benghalensis in S. almum diet improved intake, digestibility and N intake, suggesting its potential use as a feed supplement.     

Snail herbivory on submerged macrophytes and nutrient release: Implications for macrophyte management

Radix swinhoei (H. Adams) is a freshwater snail commonly found in shallow regions of Lake Taihu. This research estimated, based on experiments, the consumption rates of R. swinhoei on three young submerged plants (Vallisneria spiralis, Hydrilla verticillata and Potamogeton malaianus) and its rates of nutrient release. Results showed that the snails consumed V. spiralis at the highest rate (23.34 mg g⁻¹ d⁻¹), P. malaianus at a lower rate (11.97 mg g⁻¹ d⁻¹), and H. verticillata at the lowest rate (7.04 mg g⁻¹ d⁻¹). The consumption rates on V. spiralis varied significantly, with snail size, ranging from 13.63 mg g⁻¹ d⁻¹ for large-size snails to 143.42 mg g⁻¹ d⁻¹ for small-size ones.The average nutrient release rates of snails grazing on different macrophytes were 45.93 μg PO₄-P and 0.58 mg NH₄-N g⁻¹ d⁻¹. The food species had a significant effect on NH₄-N release rates but not on PO₄-P. However, the snail size had a significant effect on PO₄-P release rates and not on NH₄-N. The present study indicates that through selective grazing and nutrient release, snails may impose a significant impact on the macrophyte community, which should be considered in managing the macrophytes of a lake.     

Age and growth of the blackchin guitarfish Glaucostegus cemiculus (Geoffroy Saint-Hilaire, 1817) from Iskenderun Bay (Northeastern Mediterranean)

Between September 2010 and June 2012, a total 291 (166 females and 125 males) blackchin guitarfish Glaucostegus cemiculus were captured by a commercial bottom trawler (F/V Coşkun Reis) in Iskenderun Bay, Turkey (northeastern Mediterranean Sea). The total length (L) and total weight (W) of the female and male guitarfish ranged between 32.0–165.0 cm and 88 g–16.68 kg, and 34.3–128.3 cm and 112 g–6.00 kg, respectively. Vertebral age estimates ranged from 0 to 8 years for females and 0 to 5 years for males. The growth models of von Bertanlanffy and Gompertz were fitted to the length at age data using the nonlinear regression method. Model selection was based on the values of the residual standard error and the Akaike's information criterion corrected for small sample size (AIC_C) associated with each fit. The von Bertalanffy growth model provided the best fitting growth curves for each sex with parameters reaching L_∞ = 187.17 cm, K = 0.195 year^-1, t₀ = −1.38 year for females, and L_∞ = 144.85 cm, K = 0.321 year^-1, t₀ = −1.13 year^-1 for males. The W–L relationship parameters did not differ significantly between sexes, the estimated values of a and b were 0.0018 and 3.11, respectively. By using these values of a and b, and also respective estimates of L_∞, the values of W_∞ were obtained as 20.53 kg for females and 9.25 kg for males. The overall percentage ratios of females and males in the samples were 57% and 43% respectively.     

The routine metabolic rate of mulloway (Argyrosomus japonicus: Sciaenidae) and yellowtail kingfish (Seriola lalandi: Carangidae) acclimated to six different temperatures

This study compared the mass-specific routine metabolic rate (RMR) of similar sized mulloway (Argyrosomus japonicus), a sedentary species, and yellowtail kingfish (Seriola lalandi), a highly active species, acclimated at one of several temperatures ranging from 10–35 °C. Respirometry was carried out in an open-top static system and RMR corrected for seawater–atmosphere O₂ exchange using mass-balance equations. For both species RMR increased linearly with increasing temperature (T). RMR for mulloway was 5.78T − 29.0 mg O₂ kg^− 0.8 h^− 1 and for yellowtail kingfish was 12.11T − 39.40 mg O₂ kg^− 0.8 h^− 1. The factorial difference in RMR between mulloway and yellowtail kingfish ranged from 2.8 to 2.2 depending on temperature. The energetic cost of routine activity can be described as a function of temperature for mulloway as 1.93T − 9.68 kJ kg^− 0.8 day^− 1 and for yellowtail kingfish as 4.04T − 13.14 kJ kg^− 0.8 day^− 1. Over the full range of temperatures tested Q₁₀ values were approximately 2 for both species while Q₁₀ responses at each temperature increment varied considerably with mulloway and yellowtail kingfish displaying thermosensitivities indicative of each species respective niche habitat. RMR for mulloway was least thermally dependent at 28.5 °C and for yellowtail kingfish at 22.8 °C. Activation energies (E_a) calculated from Arrhenius plots were not significantly different between mulloway (47.6 kJ mol^− 1) and yellowtail kingfish (44.1 kJ mol^− 1).     

Enantioselective acylation of (RS)-phenylethylamine catalysed by lipases

The enzymatic acylation of (RS)-phenylethylamine with different acyl donors catalysed by lipases, was studied in organic solvents with different hydrophobicities and in mixtures with ionic liquids ((ILs); [BMIm][BF₄], [BMIm][SCN], [BMIm][Cl] and [BMIm][PF₆]). Using lipases from Candida antarctica B (CAL-B) and from Aspergillus niger higher conversion degrees and E-values were obtained with ethyl acetate as the acyl donor. When CAL-B was used as the biocatalyst, in a two-phase system formed by [BMIm][X]/dichloromethane or [BMIm][X]/chloroform, the selectivity was better than that obtained in pure organic solvents. The selectivity was found to be related to individual anions in ILs. In this reaction, the ion effectiveness in enhancing the enzyme selectivity followed the series: Cl⁻ > SCN⁻ > BF₄⁻ > PF₆⁻ in mixtures with dichloromethane, and PF₆⁻ > BF₄⁻ > SCN⁻ > Cl⁻ in mixtures with chloroform.     

Enhanced yield of medium-chain-length polyhydroxyalkanoates from nonanoic acid by co-feeding glucose in carbon-limited, fed-batch culture

Medium-chain-length polyhydroxyalkanoates (MCL-PHAs) were produced in carbon-limited, single-stage, fed-batch fermentations of Pseudomonas putida KT2440 by co-feeding nonanoic acid (NA) and glucose (G) to enhance the yield of PHA from NA. An exponential (μ = 0.25 h⁻¹) followed by a linear feeding strategy at a NA:G ratio of 1:1 (w/w) achieved 71 g l⁻¹ biomass containing 56% PHA. Although the same overall PHA productivity (1.44 g l⁻¹ h⁻¹) was obtained when NA alone was fed at the same specific growth rate, the overall yield of PHA from NA increased by 25% (0.66 g PHA g NA⁻¹ versus 0.53 g g⁻¹) with glucose co-feeding. Further increasing glucose in the feed (NA:G = 1:1.5) resulted in a slightly higher yield (0.69 g PHA g NA⁻¹) but lower PHA content (48%) and productivity (1.16 g l⁻¹ h⁻¹). There was very little change in the PHA composition.     

Genetic parameters of a random regression model for daily feed intake of performance tested French Landrace and Large White growing pigs

Daily feed intake data of 1 279 French Landrace (FL, 1 039 boars and 240 castrates) and 2 417 Large White (LW, 2 032 boars and 385 castrates) growing pigs were recorded with electronic feed dispensers in three French central testing stations from 1992–1994. Male (35 to 95 kg live body weight) or castrated (100 kg live body weight) group housed, ad libitum fed pigs were performance tested. A quadratic polynomial in days on test with fixed regressions for sex and batch, random regressions for additive genetic, pen, litter and individual permanent environmental effects was used, with two different models for the residual variance: constant in model 1 and modelled with a quadratic polynomial depending on the day on test d_m as follows in model 2: . Variance components were estimated from weekly means of daily feed intake by means of a Bayesian analysis using Gibbs sampling. Posterior means of (co)variances were calculated using 800 000 samples from four chains (200 000 each). Heritability estimates of regression coefficients were 0.30 (FL model 1), 0.21 (FL model 2), 0.14 (LW1) and 0.14 (LW2) for the intercept, 0.04 (FL1), 0.04 (FL2), 0.11 (LW1) and 0.06 (LW2) for the linear, 0.03 (FL1), 0.04 (FL2) 0.11 (LW1) and 0.06 (LW2) for the quadratic term. Heritability estimates for weekly means of daily feed intake were the lowest in week 4 (FL1: 0.11, FL2: 0.11) and week 1 (LW1: 0.09, LW2: 0.10), and the highest in week 11 (FL1: 0.25, FL2: 0.24) and week 8 (LW1: 0.19, LW2: 0.18), respectively. Genetic eigenfunctions revealed that altering the shape of the feed intake curve by selection is difficult.     

A novel photobioreactor with transparent rectangular chambers for cultivation of microalgae

An open tank photobioreactor containing transparent rectangular chambers (TRCs) was developed to improve the photosynthetic efficiency of microalgal cultivation. The TRCs, made of transparent acrylic, conducted light deep into the photobioreactor, especially at high cell concentrations. The average irradiance, I_av, was calculated by Lambert–Beer's law, and was used to determine the light conditions in the cultivation system. The photobioreactor provided large areas of illumination that improved the effective utilization of light energy for microalgae growth and created a good artificial environment for a high rate of cell growth, even at low I_av. The biomass concentration of Chlorella sp. reached 3.745 g L⁻¹ on the 13th day, with biomass productivity of 0.340 g L⁻¹ d⁻¹. The total biomass obtained was 56% more than that of similar culture systems without TRCs.     

Growth of dinoflagellates, Ceratium furca and Ceratium fusus in Sagami Bay, Japan: The role of temperature, light intensity and photoperiod

Seasonal changes of field populations and growth rates of two dinoflagellates, Ceratium furca and Ceratium fusus, were examined in the temperate coastal water of Sagami Bay, Japan. Weekly field sampling was conducted from August 2002 to August 2003, and laboratory experiments were also carried out to investigate effects of temperature, irradiance and photoperiod on the growth rates of these two Ceratium species. In the field, the abundances of both species increased significantly from April to August 2003, were gradually decreased from November 2002 and were not observed in January 2003. C. fusus was able to increase at lower temperatures in February 2003 compared to C. furca. In the laboratory, the two species did not grow at <10 °C or >32 °C. The highest specific growth rate of C. furca was 0.72 d⁻¹ at 24 °C and 600 μmol m⁻² s⁻¹. Optimum growth rates (>0.4 d⁻¹) of C. furca were observed at temperatures from 18 to 28 °C and at irradiances from 216 to 796 μmol m⁻² s⁻¹. The highest growth rate of C. fusus was 0.56 d⁻¹ at 26 °C and 216 μmol m⁻² s⁻¹. Optimum growth rates of C. fusus were observed at the same irradiance rage of C. furca, whereas optimum temperature range was narrower (26–28 °C). The growth curves of both species indicated saturation of the growth rates when light intensity was above 216 μmol m⁻² s⁻¹, and did not show photoinhibition at irradiances up to 796 μmol m⁻² s⁻¹. The specific growth rates of both Ceratium species were clearly decreased at L:D = 10:14 relative to those at L:D = 14:10 and L:D = 12:12. The present study indicates the two Ceratium species can adapt to a wide range of temperature and irradiance.