Optimization of spray-drying conditions for the large-scale preparation of Bacillus thuringiensis var. israelensis after downstream processing

Reduction of water activity in the formulations of mosquito biocontrol agent, Bacillus thuringiensis var. israelensis is very important for long term and successful storage. A protocol for spray drying of B. thuringiensis var. israelensis was developed through optimizing parameters such as inlet temperature and atomization type. A indigenous isolate of B. thuringiensis var. israelensis (VCRC B-17) was dried by freeze and spray drying methods and the moisture content and mosquito larvicidal activity of materials produced by the two methods were compared. The larvicidal activity was checked against early fourth instars Aedes aegypti larvae. Results showed that the freeze-dried powders retained the larvicidal activity fairly well. The spray-dried powder moderately lost its larvicidal activity at different inlet temperatures. Between the two types of atomization, centrifugal atomization retained more activity than the nozzle type atomization. Optimum inlet temperature for both centrifugal and nozzle atomization was 160 degrees C. Keeping the outlet temperature constant at 70 degrees C the moisture contents for the spray-dried powders through centrifugal atomization and freeze-dried powders were 10.23% and 11.80%, respectively. The LC(50) values for the spray-dried and freeze-dried powders were 17.42 and 16.18 ng/mL, respectively. Spore count of materials before drying was 3 x 10(10) cfu/mL and after spray drying through nozzle and centrifugal atomization at inlet and outlet temperature of 160 degrees C/70 degrees C were 2.6 x 10(9) and 5.0 x 10(9) cfu/mL, respectively.     

Toxicity assessment of the antifouling compound zinc pyrithione using early developmental stages of the ascidian Ciona intestinalis

Abstract

This study investigated the toxicity of zinc pyrithione (Zpt) on the early stages of development of the ascidian Ciona intestinalis. Larval morphological abnormalities were studied after the exposure of C. intestinalis embryos at different stages of development. The median effective concentrations (EC₅₀) ranged from 226–590 nM. The larval settlement stage was the most sensitive to Zpt. Toxic effects of Zpt on larval settlement were detected at 9 nM (EC₁₀). The inhibition of C. intestinalis embryonic development was also used to study the loss of toxicity in Zpt solutions exposed to direct sunlight and laboratory UV light. The results showed that the toxicity of Zpt solutions decreased but did not disappear after 4 h exposure to direct sunlight (EC₅₀ = 484 nM) or UV light (EC₅₀ = 453 nM), compared to control Zpt solutions prepared in dark conditions. On the basis of the present data, predicted no effect concentrations of Zpt to C. intestinalis larvae are lower than predicted environmental concentrations of Zpt in certain polluted areas and therefore, may pose a risk to C. intestinalis populations.     

A bioassay to assess the potential effects of sediment resuspension on phytoplankton community composition

A laboratory assay (SAGA or Sediment Algal Growth Assay) was developed to assess the potential impact of sediment resuspension on the structure of phytoplankton communities, and to evaluate the effectiveness of various sediment treatments in decreasing the abundance of blue-green algae in the event of sediment resuspension during storms. In assays with sediment from eutrophic Akanoi Bay, Lake Biwa, Japan, 7–11 species of phytoplankton seeded from the sediments grew during the 3-week assay indicating that sediment resuspension has the potential to increase both phytoplankton biomass and species diversity. Treatment of sediments with Ca(NO3)2 substantially decreased phytoplankton biomass (measured as chlorophyll concentration) in assays with sediments from Akanoi Bay and the North Basin of Lake Biwa. Further, among various oxidation treatments of sediments, Ca(NO3)2 was most effective in decreasing or preventing filamentous blue-green algal growth in N- and P-replete media. In contrast, when sediments were added to P-limited phytoplankton dominated by green algae and diatoms, no growth of blue-green algae occurred regardless of sediment treatment. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transformation of carbon tetrachloride under sulfate reducing conditions

The removal of carbon tetrachloride under sulfate reducing conditions was studied in an an aerobic packed-bed reactor. Carbon tetrachloride, up to a concentration of 30 μM, was completely converted. Chloroform and dichloromethane were the main transformation products, but part of the carbon tetrachloride was also completely dechlorinated to unknown products. Gram-positive sulfate-reducing bacteria were involved in the reductive dechlorination of carbon tetrachloride to chloroform and dichloromethane since both molybdate, an inhibitor of sulfate reduction, and vancomycin, an inhibitor of gram-positive bacteria completely inhibited carbon tetrachloride transformation. Carbon tetrachloride transformation by these bacteria was a cometabolic process and depended on the input of an electron donor and electron acceptor (sulfate). The rate of carbon tetrachloride transformation by sulfate reducing bacteria depended on the type of electron donor present. A transformation rate of 5.1 nmol·ml^-1·h^-1 was found with ethanol as electron donor. At carbon tetrachloride concentrations higher than18 μM, sulfate reduction and reductive dechlorination of carbon tetrachloride decreased and complete inhibition was observed at a carbon tetrachloride concentration of 56.6 μM. It is not clear what type of microorganisms were involved in the observed partial complete dechlorination of carbon tetrachloride. Sulfate reducing bacteria probably did not play a role since inhibition of these bacteria with molybdate had no effect on the complete dechlorination of carbon tetrachloride. This revised version was published online in August 2006 with corrections to the Cover Date.     

皂荚果实中皂苷O的分离鉴定及毒性研究

采用乙醇提取、正丁醇萃取、常压硅胶柱反复层析的方法,并结合杀鼠活性追踪,从豆科植物皂荚(Gleditsiasinensis Lam.)的果实中分离到一个含有7个糖基的三萜皂苷,通过TLC、mp、IR、MS、1 H-NMR和13 C-NMR等方法鉴定为3-O-β-D-吡喃木糖基-(1→2)-α-L-吡喃阿拉伯糖基-(1→6)-β-D-吡喃葡萄糖基齐墩果酸28-O-β-D-吡喃木糖基-(1→3)-β-D-吡喃木糖基-(1→4)-α-L-吡喃鼠李糖基-(1→2)-[(6S,2E)-6-羟基-2,6-二甲基-2,7-辛二烯醇-(1→3)-(6′S,2′E)-6′-羟基-2′,6′-二甲基-2′,7′-辛二烯醇-(1→6)]-β-D-吡喃葡萄糖酯[即皂荚皂苷O(GleditsiosidesO)]。对小鼠的急性毒性测定结果表明,试鼠对皂荚皂苷O经口灌胃的耐受量为160～400mg/kg,半数致死剂量LD50=249.52mg/kg,95%可信区间为224.81～276.95mg/kg;皂荚皂苷O对小鼠的急性毒性大于皂荚皂苷A。研究结果表明,皂荚皂苷O为皂荚的主要杀鼠活性成分。     

Region specific increase in the antioxidant enzymes and lipid peroxidation products in the brain of rats exposed to lead

The objective of this study is to determine the effect of lead (pb) on antioxidant enzymes and lipid peroxidation products in different regions of rat brain. Wistar male rats were treated with lead acetate (500 ppm) through drinking water for a period of 8 weeks. Control animals were maintained on sodium acetate. Treated and control rats were sacrificed at intervals of 1st, 4th and 8th week and the whole brains were dissected on ice into four regions namely the cerebellum, the hippocampus, the frontal cortex and the brain stem. Antioxidant enzymes namely catalase and superoxide dismutase in all the four regions of brain were determined. In addition, lipid peroxidation products were also estimated. The results indicated a gradual increase in the activity of antioxidant enzymes in different regions of the brain and this response was time-dependent. However, the increase was more in the cerebellum and the hippocampus compared to other regions of the brain. The lipid peroxidation products also showed a similar trend suggesting increased effect of lead in these two regions of the brain. The data indicated a region-specific oxidative stress in the brain exposed to lead.     

Sensitivity of different Lupinus species to calcium under a low phosphorus supply

To study mechanism underpinning the calcifuge habit of some Lupinus species, especially under low‐phosphorus (P) conditions, Lupinus species that were likely to respond differently to calcium (Ca) availability were assembled, and the sensitivity to Ca under a low‐P supply was assessed. Seven Lupinus species (9 genotypes, L. albus L. cv Kiev, L. albus L. P26766, L. angustifolius L. cv Mandelup, L. angustifolius L. P26723, L. luteus L. cv Pootalong, L. hispanicus ssp. bicolor Boiss. and Reut. P22999, L. pilosus Murr. P27440, L. cosentinii Guss. P27225, and L. atlanticus Gladst. P27219) were grown hydroponically at 10 or 6000 μM Ca. Leaf symptoms, gas exchange and biomass were recorded; leaf and root nutrient concentrations were analysed, and the leaf cell types in which Ca and P accumulated were determined using elemental X‐ray microanalyses. Calcium toxicity was demonstrated for L. angustifolius P26723, L. hispanicus ssp. bicolor. P22999, and L. cosentinii P27225, whereas the other species were tolerant of a high Ca supply under low‐P conditions. In addition, genotypic differences in Ca toxicity were found within L. angustifolius. Most Ca accumulated in the mesophyll cells in all species, whereas most P was located in epidermal cells.     

Toxicity of the chlorpyrifos-based pesticide Termifos®: effects on behaviour and biochemical and haematological parameters of African catfish Clarias gariepinus

The present study, conducted in 2012, determined the toxicity of the chlorpyrifos-based pesticide Termifos^® and its effects on behaviour and biochemical and haematological parameters in juvenile African catfish Clarias gariepinus. The 96 h LC₅₀, estimated by probit analysis in a semi-static bioassay experiment, was 0.861 mg l^-1. Fish were exposed to two sublethal concentrations, one-fifth LC₅₀ = c. 172 µg l^-1 and one-tenth LC₅₀ = c. 86 µg l^-1, and blood was sampled at 5, 10 and 15 d post-exposure. Fish exposed to 172 µg l^-1 Termifos showed significantly lower red blood cell count and haematocrit values, and both sublethal concentrations significantly lowered the white blood cell count. The haemoglobin level did not change significantly at either dosage. Mean corpuscular haemoglobin, mean corpuscular volume and mean corpuscular haemoglobin concentration values were significantly elevated, compared to the control specimens. Glucose concentration showed an ascending trend and a positive correlation with Termifos concentration, whereas protein concentration declined and was negatively correlated with pesticide concentration. Following exposure to the pesticide, the fish showed remarkable behavioural abnormalities including erratic swimming movements, hyperactivity, faster opercular movement, surfacing to gulp air, secretion of copious mucus and loss of balance. Chlorpyrifos should be applied with caution in the environment, especially near water bodies, to avoid the possible ecotoxicological risks associated with its use.     

Effects of Cadmium, Lead, Mercury and Zinc on °-Aminolevulinic Acid Dehydratase Activity from Radish Leaves

The purpose of the present study was to investigate the in vitro and the in vivo effects of cadmium, zinc, mercury and lead on -aminolevulinic acid dehydratase (ALA-D) activity from radish leaves. The in vivo effect of these metals on growth, DNA and protein content was also evaluated. The results demonstrated that among the elements studied Cd²⁺ presented the highest toxicity for radish. 50% inhibition of ALA-D activity (IC₅₀) in vitro was at 0.39, 2.39, 2.29, and 1.38 mM Cd²⁺, Zn²⁺, Hg²⁺ and Pb²⁺, respectively. After in vivo exposure Cd²⁺, Zn²⁺, Hg²⁺ and Pb²⁺ inhibited ALA-D by about 40, 26, 34 and 15%, respectively. Growth was inhibited by about 40, 10, 25, and 5% by Cd²⁺, Zn²⁺, Hg²⁺, and Pb²⁺, respectively. DNA content was reduced about 35, 30, 20, and 10% for Cd²⁺, Zn²⁺, Hg²⁺, and Pb²⁺, respectively. The metal concentration in radish leaves exposed to Cd²⁺, Zn²⁺, Hg²⁺, and Pb²⁺ was 18, 13, 6, and 7 mol g^–1, respectively. The marked ability of radish to accumulate Cd²⁺ and Zn²⁺ raises the possibility of using this vegetable as a biomonitor of environmental contamination by these metals.     

重金属离子对黑斑蛙胚胎及蝌蚪的毒性影响

本文研究了5种重金属对黑斑蛙胚胎期及蝌蚪期的毒性作用,结果表明,各重金属离子对胚胎期中的孵化期和开口期毒性较大,其余各期毒性较小。各重金属离子对胚胎的毒性顺序为Hg