Toxicity of silver nanoparticles on the brain of Oreochromis niloticus and Tilapia zillii

BackgroundSilver nanoparticles (Ag-NPs) are widely used nowadays in a variety of commercial applications including medical, health care, textiles and household supplies.ObjectivesThe current study was designed to determine the median lethal dose (LC₅₀) of Ag-NPs on Oreochromis niloticus and Tilapia zillii.MethodsAcute and sub-acute toxicity study of the Ag-NPs on brain tissues was carried out using different concentrations of the NPs at 2 mg L and 4 mg L. These concentrations were dispersed in deionized water with the exception of the control groups in the experiments. Biochemical and molecular analysis were conducted on tissue homogenates in order to evaluate the potential effects of NPs on the antioxidant system.ResultsThe Ag-NP acute toxicity (96 h LC₅₀) values of 19.5 ± 2 and 20 ± 2.4 mg/L were reported for O. niloticus and T. zillii respectively. Fish exposed to 2 mg/L Ag-NPs did not show any significant change in the levels of reduced glutathione (GSH), total glutathione (tGSH) levels, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activity or genes expression and malondialdehyde (MDA) level. In contrary, a dose of 4 mg/L showed a significant reduction in the levels all the above-mentioned parameters except in MDA level where it was significantly induced.ConclusionResults indicate that exposure of O. niloticus and T. zillii to Ag-NPs (4 mg/L) has deleterious effects on brain antioxidant system, whereas a dose of 2 mg/L has no effects.     

Insecticidal properties of Pimpinella anisum essential oils against the Culex quinquefasciatus and the non-target organism Daphnia magna

The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC₅₀ for the 2nd to 4th instar larvae was estimated as 26–27 μL·L^− 1 and 15–19 μL·L^− 1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)₅₀ was estimated as 9.3 μL mL^− 1 (spray test), 1.9 μL L^− 1 (fumigation test) and 0.6 μg cm^− 2 (tarsal test), and for trans-Anethole as 8.1 μL mL^− 1 (spray test), 2.1 μL L^− 1 (fumigation test) and 0.4 μg cm^− 2 (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)₉₉ of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235 min depending on the larval instar, and from 9 to 180 min when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied.The essential oil and trans-Anethole were toxic for Daphnia magna (62–92% mortality) and significantly reduced its fertility at high concentrations (35–50 μL mL^− 1) and long exposure (48 h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6 h) and/or lower concentrations (20 μL mL^− 1).Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides.     

Bench-scale fermentation of Trichoderma viride on wastewater sludge: Rheology,lytic enzymes and biocontrol activity

Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 10⁷ CFU mL⁻¹ at 96 h) was obtained at 30 g L⁻¹ suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L⁻¹ suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL⁻¹ at 30 g L⁻¹ suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L⁻¹ compared to 30 and 25 g L⁻¹. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, k_La at 35 g L⁻¹ did not increase in comparison to 30 g L⁻¹ due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.     

Accumulation and detoxification dynamic of cyanotoxins in the freshwater shrimp Palaemonetes argentinus

The uptake and accumulation of microcystin-LR (MC-LR) in the shrimp Palaemonetes argentinus was investigated using both laboratory and field assays. Shrimps were exposed in aquarium during 1, 2, 3 and 7 days to 1, 10 and 50 μg L⁻¹ MCLR. Accumulation (0.7 ± 0.2 μg MC-LR g⁻¹) was observed after three days exposures to 50 μg L⁻¹ toxin. Then, shrimps were relocated in fresh water (free of MCLR) to verify the detoxification dynamic, showing a drop to 0.18 ± 0.01 μg MCLR g⁻¹ after three days. The activity of glutathione-S-transferase, measured in the microsomal fraction (mGST), was significantly increased during the exposure period, with further increment during the detoxification period. Furthermore, cytosolic GST (sGST) and glutathione reductase (GR) increased their activities during detoxification, while inhibition was observed for catalase (CAT) with no significant changes for glutathione peroxidase (GPx). Current results suggest that GSH conjugation could be an important MC detoxification mechanism in P. argentinus and that MCLR induce oxidative stress in this shrimp.Field exposures were carried out in San Roque Reservoir (Córdoba, Argentina) after a cyanobacteria bloom. Nodularin (Nod) presence was measured for the first time in this waterbody (0.24 ± 0.04 μg L⁻¹), being the first report of Nod in South America freshwaters. Nod was also detected in Palaemonetes argentinus (0.16 ± 0.03 μg g⁻¹) after three weeks of exposure in this reservoir, with the concomitant activation of mGST, sGST and CAT.Although internal doses of Nod were low throughout the exposure, they were enough to cause biochemical disturbances in Palaemonetes argentinus.Further laboratory studies on Nod accumulation and antioxidant responses in Palaemonetes argentinus are necessary to fully understand these field results. P. argentinus should be considered a potential vector for transferring cyanotoxins to higher trophic levels in aquatic environments.     

Effects of flooding on photosynthesis and root respiration in saltcedar (Tamarix ramosissima), an invasive riparian shrub

The introduced shrub Tamarix ramosissima invades riparian zones, but loses competitiveness under flooding. Metabolic effects of flooding could be important for T. ramosissima, but have not been previously investigated. Photosynthesis rates, stomatal conductance, internal (intercellular) CO₂, transpiration, and root alcohol dehydrogenase (ADH) activity were compared in T. ramosissima across soil types and under drained and flooded conditions in a greenhouse. Photosynthesis at 1500 μmol quanta m⁻² s⁻¹ (A₁₅₀₀) in flooded plants ranged from 2.3 to 6.2 μmol CO₂ m⁻² s⁻¹ during the first week, but A₁₅₀₀ increased to 6.4–12.7 μmol CO₂ m⁻² s⁻¹ by the third week of flooding. Stomatal conductance (g_s) at 1500 μmol quanta m⁻² s⁻¹ also decreased initially during flooding, where g_s was 0.018 to 0.099 mol H₂O m⁻² s⁻¹ during the first week, but g_s increased to 0.113–0.248 mol H₂O m⁻² s⁻¹ by the third week of flooding. However, photosynthesis in flooded plants was reduced by non-stomatal limitations, and subsequent increases indicate metabolic acclimation to flooding. Root ADH activities were higher in flooded plants compared to drained plants, indicating oxygen stress. Lower photosynthesis and greater oxygen stress could account for the susceptibility of T. ramosissima at the onset of flooding. Soil type had no effect on photosynthesis or on root ADH activity. In the field, stomatal conductance, leaf water potential, transpiration, and leaf δ¹³C were compared between T. ramosissima and other flooded species. T. ramosissima had lower stomatal conductance and water potential compared to Populus deltoides and Phragmites australis. Differences in physiological responses for T. ramosissima could become important for ecological concerns.     

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 NH4+ and NO3− on growth,resource allocation and nitrogen uptake kinetics of Phragmites australis and Glyceria maxima

The effects of NH₄⁺ or NO₃⁻ on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g⁻¹ d⁻¹), whereas the growth rate of Glyceria was 16% higher in NH₄⁺-N cultures than in NO₃⁻-N cultures (mean = 66.7 and 57.4 mg g⁻¹ d⁻¹ of NH₄⁺ and NO₃⁻ treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH₄⁺ cultures than in NO₃⁻ cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH₄⁺ treated plants by 16%. The tissue NH₄⁺ concentration (mean = 1.6 μmol g fresh wt⁻¹) was not affected by N treatment, whereas NO₃⁻ contents were higher in NO₃⁻ (mean = 1.5 μmol g fresh wt⁻¹) than in NH₄⁺ (mean = 0.4 μmol g fresh wt⁻¹) treated plants. In Phragmites, NH₄⁺ (mean = 1.6 μmol g fresh wt⁻¹) and NO₃⁻ (mean = 0.2 μmol g fresh wt⁻¹) contents were not affected by the N regime. Species did not differ in NH₄⁺ (mean = 56.5 μmol g⁻¹ root dry wt h⁻¹) and NO₃⁻ (mean = 34.5 μmol g⁻¹ root dry wt h⁻¹) maximum uptake rates (V_max), and V_max for NH₄⁺ uptake was not affected by N treatment. The uptake rate of NO₃⁻ was low in NH₄⁺ treated plants, and an induction phase for NO₃⁻ was observed in NH₄⁺ treated Phragmites but not in Glyceria. Phragmites had low K_m (mean = 4.5 μM) and high affinity (10.3 l g⁻¹ root dry wt h⁻¹) for both ions compared to Glyceria (K_m = 6.3 μM, affinity = 8.0 l g⁻¹ root dry wt h⁻¹). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH₄⁺-N source may participates in the observed success of Glyceria at NH₄⁺ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites.     

Continuous succinic acid production by Actinobacillus succinogenes in a biofilm reactor: Steady-state metabolic flux variation

Continuous anaerobic fermentations were performed in a novel external-recycle, biofilm reactor using d-glucose and CO₂ as carbon substrates. Succinic acid (SA) yields were found to be an increasing function of glucose consumption with the succinic acid to acetic acid ratio increasing from 2.4 g g⁻¹ at a glucose consumption of 10 g L⁻¹, to 5.7 g g⁻¹ at a glucose consumption of 50 g L⁻¹. The formic acid to acetic acid ratio decreased from an equimolar value (0.77 g g⁻¹) at a glucose consumption of 10 g L⁻¹ to a value close to zero at 50 g L⁻¹. The highest SA yield on glucose and highest SA titre obtained were 0.91 g g⁻¹ and 48.5 g L⁻¹ respectively. Metabolic flux analysis based on the established C₃ and C₄ metabolic pathways of Actinobacillus succinogenes revealed that the increase in the succinate to acetate ratio could not be attributed to the decrease in formic acid and that an additional source of NADH was present. The fraction of unaccounted NADH increased with glucose consumption, suggesting that additional reducing power is present in the medium or is provided by the activation of an alternative metabolic pathway.     

Comparative assessment of single and joint effects of diuron and Irgarol 1051 on Arctic and temperate microalgae using chlorophyll a fluorescence imaging

Ship groundings and ice-breakers can cause pollution of the polar environment with antifouling biocides such as diuron and Irgarol 1051. The present study used pulse amplitude modulated fluorometry to compare single and joint toxicities of diuron and Irgarol 1051 on two freshwater taxa of microalgae (Chlorella and Chlamydomonas) originating from Arctic and temperate regions. 30 min acute toxicity tests using chlorophyll a (Chl a) fluorescence revealed that Arctic strains of microalgae were more sensitive to herbicides than their temperate counterparts. Diuron and Irgarol 1051 had equal toxicities in the Arctic species, while Irgarol 1051 was more toxic (EC₅₀ = 5.55–14.70 μg L⁻¹) than diuron (EC₅₀ = 12.90–>40 μg L⁻¹) in the temperate species. Toxicity assessment of various mixtures of diuron and Irgarol 1051 revealed antagonistic, additive, and synergistic effects. Our data suggest that herbicides can adversely affect photosynthesis in Arctic microalgae at relatively low levels, and their impact can increase under complex mixture conditions.     

Isolation and bioelectrochemical characterization of novel fungal sources with oxidasic activity applied in situ for the cathodic oxygen reduction in microbial fuel cells

Brazilian filamentous fungi Rhizopus sp. (SIS-31), Aspergillus sp. (SIS-18) and Penicillium sp. (SIS-21), sources of oxidases were isolated from Caatinga's soils and applied during the in situ cathodic oxygen reduction in fuel cells. All strains were cultivated in submerged cultures using an optimized saline medium enriched with 10 g L⁻¹ of glucose, 3.0 g L⁻¹ of peptone and 0.0005 g L⁻¹ of CuSO₄ as enzyme inducer. Parameters of oxidase activity, glucose consumption and microbial growth were evaluated. In-cell experiments evaluated by chronoamperometry were performed and two different electrode compositions were also compared. Maximum current densities of 125.7, 98.7 and 11.5 μA cm⁻² were observed before 24 h and coulombic efficiencies of 56.5, 46.5 and 23.8% were obtained for SIS-31, SIS-21 and SIS-18, respectively. Conversely, maximum power outputs of 328.73, 288.80 and 197.77 mW m⁻³ were observed for SIS-18, SIS-21 and SIS-31, respectively. This work provides the primary experimental evidences that fungi isolated from the Caatinga region in Brazil can serve as efficient biocatalysts during the oxygen reduction in air-cathodes to improve electricity generation in MFCs.     

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.     

Seasonal variations in photosynthetic irradiance response curves of macrophytes from a Mediterranean coastal lagoon

The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O₂ g⁻¹ dw h⁻¹ and 9.1 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O₂ g⁻¹ dw h⁻¹ and 2.6 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹ respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to R_d (ranging 6.7–794 μmol O₂ g⁻¹ dw h⁻¹, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum).     

β-carotene production from soap stock by loofa-immobilized Rhodotorula rubra in an airlift photobioreactor

In this study, the soap stock as a sole carbon source was used for growing a carotenoid producing yeast (Rhodotorula rubra). The application of soap stock resulted in increase of carotenoids yield up to 5.36 folds when compared with the grown cultures on glucose. On the best Monod equation fitted on the specific growth rate (μ) data, the maximum specific growth rate (μ_m) and half-saturation concentration (K_S) were respectively determined at 0.064 h⁻¹ and 3.26 g L⁻¹ for total fatty acids presented in soap stock. Further tests on the carotenogenesis process were carried out in a cell-immobilized airlift photobioreactor where the natural loofa sponge was used for immobilization of the cells. The performance of the bioreactor was statistically studied by the response surface methodology (RSM) where aeration rate of 0.11 vvm and light irradiation intensity of 2517 Lx provided an optimum condition for producing β-carotene with a specific production rate of 22.65 mg g_cell⁻¹ day⁻¹.     

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.     

Volatile fatty acids accumulation and rhamnolipid generation in situ from waste activated sludge fermentation stimulated by external rhamnolipid addition

The solubilization and acidification of waste activated sludge (WAS) were apparently enhanced by external rhamnolipid (RL) addition. The maximum solute carbohydrate concentrations increased linearly from 48 ± 5 mg COD L⁻¹ in the un-pretreated WAS (blank) to 566 ± 19 mg COD L⁻¹, and protein increased from 1050 ± 8 to 3493 ± 16 mg COD L⁻¹ at RL dosage of 0.10 g g⁻¹ TSS. The highest VFAs concentration peaked at 3840 mg COD L⁻¹ at RL dosage of 0.04 g g⁻¹ TSS, which was 4.24-fold higher than the blank test. RL was generated in situ during WAS fermentation when external RL was added. It was detected that RL concentration was increased from initial 880 ± 92 mg L⁻¹ to 1312 ± 7 mg L⁻¹ at the end of 96 h with RL dosage of 0.04 g g⁻¹ TSS, which was increased to 1.49-fold. Meanwhile, methane production was notably reduced to a quite low level of 2.0 mL CH₄ g⁻¹ VSS, showing effective inhibition of methanogens by RL (58.8 mL CH₄ g⁻¹ VSS in the blank). In addition, the activity of hydrolytic enzymes (protease and α-glucosidase) was enhanced accordingly. VFAs accumulation and RL generation in situ demonstrated that the additional RL substantially performed enhanced biological effects for waste activated sludge fermentation.     

Expression analysis and biochemical characterization of beans plants biofortificated with zinc

The present work was carried out in greenhouse conditions at the Centro de Investigación en Alimentación y Desarrollo AC in Delicias, Chihuahua, México. Four different concentrations (0, 25, 50 and 100 μM L⁻¹) of Zn chelate and sulfate were used to study the antioxidant system of Phaseolus vulgaris L. Three genes related with antioxidant activity [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT)] were selected for expression study. Results showed that when Zn chelate at 50 and 100 μM L⁻¹ were applied SOD was repressed and GSH-Px expression was low at 0, 25 and 100 μM L⁻¹ while with sulfate form SOD expression was low and GSH-Px expression was strong in all treatment. CAT was highly expressed in all form and treatments. For a biochemical study the same enzymes were spectrophotometrically measured. SOD activity shows differences in both forms of Zn, chelate form was different at 25, 50 and 100 μM L⁻¹ with less activity at 100 μM L⁻¹ and sulfate treatment shows differences in all concentrations used. GSH-Px activity shows significant differences with sulfate form at 25, 50 μM L⁻¹ where at 50 μM the activity was higher and low at 100 μM L⁻¹, CAT does not exhibit significant differences but with chelate treatment at 50–100 μM L⁻¹ the activity was higher compared to sulfate. Finally, to raise the Zn concentration in bean under biofortification program is a promising strategy in cropping systems in order to increase the ingestion of zinc and antioxidant capacity in the general population and provided the benefits that this element offered in human health.     

d- and l-lactic acid production from fresh sweet potato through simultaneous saccharification and fermentation

The aim of this study was to develop a bioprocess for l- and d-lactic acid production from raw sweet potato through simultaneous saccharification and fermentation by Lactobacillus paracasei and Lactobacillus coryniformis, respectively. The effects of enzyme and nitrogen source concentrations as well as of the ratio of raw material to medium were investigated. At dried material concentrations of 136.36–219.51 g L⁻¹, yields of 90.13–91.17% (w/w) and productivities of 3.41–3.83 g L⁻¹ h⁻¹ were obtained with lactic acid concentrations as high as 198.32 g L⁻¹ for l-lactic acid production. In addition, d-lactic acid was produced with yields of 90.11–84.92% (w/w) and productivities of 2.55–3.11 g L⁻¹ h⁻¹ with a maximum concentration of 186.40 g L⁻¹ at the same concentrations of dried material. The simple and efficient process described in this study will benefit the tuber and root-based lactic acid industries without requiring alterations in plant equipment.     

Synthesis and biological evaluation of new bis-indolone-N-oxides

A series of bis-indolone-N-oxides, 1a–f, was prepared from bis(ethynyl)benzenes and o-halonitroaryls and studied for their in vitro antiplasmodial activities against Plasmodium falciparum and representative strains of bacteria and candida as well as for their cytotoxicity against a human tumor cell line (MCF7). They did not cause any haemolysis (300 μg mL⁻¹). Of the synthesized bis-indolones, compound 1a had the most potent antiplasmodial activity (IC₅₀ = 0.763 μmol L⁻¹ on the FcB1 strain) with a selectivity index (CC₅₀ MCF7/IC₅₀ FcB1) of 35.6. No potency against the tested microbial strains was observed.     

Evaluation of the effects of light intensity on growth of the benthic dinoflagellate Ostreopsis sp. 1 using a newly developed photoirradiation-culture system and a novel regression analytical method

Benthic dinoflagellates of the genus Ostreopsis are found all over the world in temperate, subtropical, and tropical coastal regions. Our recent studies revealed that a putative “cryptic” species of Ostreopsis ovata is present widely along Japanese coasts. This organism, Ostreopsis sp. 1, possesses palytoxin analogs and thus its toxic blooms may be responsible for potential toxification of marine organisms. To evaluate the bloom dynamics of Ostreopsis sp. 1, the present study examined the growth responses of Ostreopsis sp. 1 strain s0716 to various light intensities (photon flux densities: μmol photons m⁻² s⁻¹) using a newly devised photoirradiation-culture system. This novel system has white light-emitting diodes (LEDs) capable of more closely simulating the wavelength spectrum of light entering the oceanic water column than do fluorescent tubes and halogen lamps. In this system, the light intensity of the white LEDs was reduced through two polarizing filters by varying the rotation angles of the filters. Thereby, the new system was capable of culturing microalgae under well-controlled light intensity conditions. Ostreopsis sp. 1 grew proportionally when light intensity was increased from 49.5 to 199 μmol photons m⁻² s⁻¹, but its growth appeared to be inhibited slightly at ≥263 μmol photons m⁻² s⁻¹. The relationship between observed growth rates and light intensity was calculated at R > 0.99 (P < 0.01) using a regression analysis with a modified equation of the photosynthesis-light intensity (P-L) model. The equation determined the critical light intensities for growth of Ostreopsis sp. 1 and the organism's growth potential as follows: (1) the threshold light intensity for growth: 29.8 μmol photons m⁻² s⁻¹; (2) the optimum light intensity (L_m) giving the maximum growth rate (μ_max = 0.659 divisions day⁻¹): 196 μmol photons m⁻² s⁻¹; (3) the optimum light intensity range (L_opt) giving ≥95% μ_max: 130–330 μmol photons m⁻² s⁻¹; (4) the semi-optimum range (L_sopt) giving ≥80% μ_max: 90 to over 460 μmol photons m⁻² s⁻¹. The L_sopt represents 4.5–23% ambient light intensity present in surface waters off of a temperate region of the Japanese coast, Tosa Bay; putatively, this semi-optimum range of light intensity appears at depth of 12.9–27.8 m. Considering these issues, our data indicate that Ostreopsis sp. 1 in coastal environments may form blooms at ca. ∼28 m depth in regions along Japanese coasts.     

Poly-β-hydroxybutyrate/ectoine co-production by ectoine-excreting strain Halomonas salina

The ectoine-excreting bacterial strain of Halomonas salina was employed in the co-production of poly-β-hydroxybutyrate (PHB) and ectoine (Ect) during a fermentation process (PHB/Ect co-production). An efficient PHB/Ect co-production process was carried out at low NaCl concentration (30 g L⁻¹). It was established using ¹H Nuclear Magnetic Resonance spectroscopy that H. salina produces PHB. The effects of the NaCl concentration, the initial C/N ratio, the phosphate concentration and mixed carbon sources were investigated with respect to PHB/Ect co-production. The PHB/Ect co-production system comprised growing and non-growing cell phases and was developed with NaCl concentration of 30 g L⁻¹. The optimal conditions for PHB/Ect co-production by the ectoine-excreting strain of H. salina were 30 g L⁻¹ NaCl, with an initial C/N ratio of 15, an initial phosphate concentration of 12 g L⁻¹ and mixed carbon sources of 55 g L⁻¹ glucose and 25 g L⁻¹ monosodium glutamate. Using a PHB/Ect co-production system with growing and non-growing cell phases prevents the inhibition of PHB synthesis by high concentration of NaCl and significantly reduces ectoine degradation. PHB and ectoine concentrations as high as 35.3 g L⁻¹ and 8.6 g L⁻¹, respectively, were achieved. The efficient co-production of PHB and ectoine at a low NaCl concentration has been realised.