Kateřina Demnerová

Absorption and translocation of polybrominated diphenyl ethers (PBDEs) by plants from contaminated sewage sludge

Polybrominated diphenyl ethers (PBDEs) are used as additive flame retardants. PBDEs are persistent, bioaccumulative and toxic compounds. They are often detected in sewage sludge which is applied on agricultural soils as fertilizer. The objective of this study was to find out whether plants are able to accumulate and translocate PBDEs. Tobacco (Nicotiana tabacum) and nightshade (Solanum nigrum) were planted in pots containing contaminated sewage sludge and uncontaminated substrate. After 6 months of plant cultivation in sewage sludge up to 15.4 ng g(-1) dw and 76.6 ng g(-1) dw of PBDE congeners--BDE 47, BDE 99 and BDE 100---were accumulated in the nightshade and tobacco tissue, respectively. Corresponding values in plants vegetated in the control garden substrate were 10 times lower. The bioconcentration factors (BCFs) of accumulated congeners were calculated. Tobacco exhibited higher BCFs values and for both plants BCFs values of BDE 47, BDE 99, BDE 100 and BDE 209 negatively correlated with their octanol-water partition coefficients (logK(ow)). The exception was decaBDE (BDE 209) which was accumulated only in tobacco tissue in the concentration of 116.8 ng g(-1) dw. The majority of PBDEs was detected in above-ground plant biomass indicating that both plants have the ability to translocate PBDEs. To our knowledge this is one of the first studies reporting the accumulation of both lower PBDEs and BDE 209 in plants. Our results suggest that absorption, accumulation and translocation of PBDEs by plants and their transfer to the food chain could represent another possible risk for human exposure.

Selective enzymic esterification of free fatty acids with n-butanol under microwave irradiation and under classical heating

Selective enzymic esterification of free fatty acids, obtained from blackcurrant oil by chemical saponification, with n-butanol using four immobilized lipases under microwave irradiation and under classical heating was studied. A positive effect of microwave irradiation on chemical yields of the products of the enzymic reactions and specificity of lipases were observed in comparison with a controlled heating in an incubator equipped with shaking (classical heating) applied during the identical enzyme-mediated processes. The maximum quantity of γ-linolenic acid (30%) was obtained with Lipozyme used as biocatalyst of the reaction under microwave irradiation. The maximum quantity of butyl γ-linolenate (20%) was obtained by a Pseudomonas cepacia lipase catalyzed esterification under classical heating.

PCB metabolism by Pseudomonas sp. P2

Abstract The degradation of Delor 103, a mixture of polychlorinated biphenyl (PCB) congeners, by Pseudomonas sp. P2, an indigenous soil bacterium was studied. In mineral medium with biphenyl as sole carbon source the extent of PCB degradation monitored by GC exceeded 70%. The efficiency of Delor 103 degradation by strain P2 was compared with that of Ralstonia eutropha H850. The addition of saccharose or agar improved PCB degradation, whereas the addition of glycerol or pyruvate substantially reduced the degradation efficiency. The presence of an amino acid mixture enhanced PCB degradation. The following chlorobenzoic acids (CBA): 2,5 CBA, 2,4 CBA, 4 CBA, 2 CBA and 2,5-diCBA were detected as metabolites of Delor 103, with 2,5-diCBA as the major product. Although 2,5-diCBA inhibited the growth of Pseudomonas sp. P2 the degradation of 2,5-diCBA was unaffected for upto 14 days.

Biodegradation of polychlorinated biphenyls and volatile chlorinated hydrocarbons in contaminated soils and ground water in field condition

Three sites with a long history of contamination with polychlorinated biphenyls (PCBs) or chlorinated ethenes (CIUs) were investigated to evaluate the natural attenuation process. Data showed that both the rates and mechanisms of biodegradation differed and that the occurrence of aerobic and anaerobic microorganisms differed qualitatively and quantitatively. Criteria for feasibility of spontaneous degradation of CIUs and PCBs in ground water and soil are formulated. (a) Congener analysis was applied to evaluate the long-term exposure of individual congeners of PCBs in the environment. In the course of approximately 20 years the small changes in congener composition could be probably due to slow biodegradation of light congeners in the relatively good oxygenated superficial layers of soil. (b) Enhanced reductive dehalogenation of PCBs was accomplished by the solid-state fermentation in reactors of 15 cubic metres of volume. Efficiency of biodegradation of individual congeners was evaluated and limits of the method were determined. (c) Different reaction rates of CIU degradation in ground water have been ascribed to the presence and/or activity of anaerobic bacteria in field conditions.

Lipase-mediated hydrolysis of blackcurrant oil

Four commercially available lipases, both free and immobilized, were tested for their ability to catalyze hydrolysis of blackcurrant (Ribes nigrum) oil using two different approaches. The lipase from Mucor miehei was studied free and immobilized in two different ways. The former series of enzymic reactions were performed in tap water at 40 degrees C, but the latter series of enzymic processes were carried out in mixtures of isooctane and phosphate buffer (in a typical 2/1 ratio of the components) at 30 degrees C. These conditions were optimized to increase and/or to maximize the yields of the products, which were priority targets in this study. A rate of hydrolysis and a selective preference of the hydrolytic enzymes towards fatty acids, with a special focus on enrichment of alpha-linolenic acid and/or gamma-linolenic acid, were studied. Higher rates of hydrolysis of the blackcurrant oil in the former series of reactions were observed with the immobilized lipase from Pseudomonas cepacia used as biocatalyst. In the latter approach, the most favorable results of the rate of hydrolysis of the target blackcurrant oil were achieved with the immobilized lipase from Mucor miehei employed as biocatalyst. Only three lipases, selected from a series of lipases tested during this investigation, displayed specificity towards alpha-linolenic acid and gamma-linolenic acid, i.e. the immobilized lipase from P. cepacia, lipase from M. miehei and lipase from P. fluorescens.

Alkane assimilation ability of Pseudomonas C12B originally isolated for degradation of alkyl sulfate surfactants

SummaryPseudomonas C12B (NCIMB 11753) is able to utilize a broad range of alkyl sulfates. The growth on n-alkanes of different chain lenght (C6–C16) was tested. Pseudomonas C12B assimilated hydrocarbons from C9–C16. Growth rate on n-decane (1%) that was chosen as the typical sole source of carbon and energy depended on oxygen supply. The addition of surfactants (Triton X-100 and Tween-80) in a nontoxic concentrations resulted in increased biomass yield. Under optimal growth conditions Pseudomonas C12B exhibited the maximal growth rate and yield with C11 as the sole carbon source.

Production of l-α-glycerophosphate oxidase by lactic acid bacteria

Various strains of lactic acid bacteria were screened for α-glycerophosphate oxidase activity (GPO). All tested strains of A. viridans and P. acidilactici gave positive results. For six chosen strains, the optimum time of production of GPO was estimated from growth curves. The best GPO producer, A. viridans CCM 2452, was chosen for optimization of nutrient media composition and for experiments with mutagenesis using UV irradiation. Mutant strains were screened for GPO activity. The best one, A. viridans 1509, exhibited good producing stability, and the yield of GPO after modification of cultivation conditions achieved more than 250% of GPO produced by the parent strain under the original cultivation conditions.

The Detection of Genetically Modified Organisms: An Overview

Genetically modified organisms (GMOs) are those whose genetic material has been altered by the insertion of a new gene or by the deletion of an existing one(s). Modern biotechnology, in particular, the rise of genetic engineering, has supported the development of GMOs suitable for research purposes and practical applications (Gepts, 2002; Novoselova, Meuwissen, & Huirne, 2007; Sakakibara & Saito, 2006). For over 20 years GM bacteria and other GM organisms have been used in laboratories for the study of gene functions (Maliga & Small, 2007; Ratledge & Kristiansen, 2006). Agricultural plants were the first GMOs to be released into the environment and placed on the market. Farmers around the world use GM soybeans, GM corn and GM cotton that are herbicide tolerant, or insect resistant, or combine several traits that reduce the costs associated with crop production (Corinne, Fernandez-Cornejo, & Goodhue, 2004). Biotech crop coverage increased globally by 13% (12 million hectares) in 2005–06 (James, 2007), and, for example, in 2007 over 70% of all soybean-producing areas were covered by GM varieties. Although transgenesis of livestock began around 20 years ago, GM farm animals, including fish, are still not as common as GM plants, the development of which began somewhat earlier. Transgenic plants are most often developed by the insertion of an alien (recombinant) gene using the soil bacteria, Agrobacterium tumefaciens, which is able to transfer a piece of its own genetic information into a plant cell. While GM plant development is at least partially based on naturally occurring mechanisms, the engineering of most transgenic livestock relies on highly technical approaches, such as pronuclear microinjection. However, newly developed techniques [sperm mediated gene transfer (SGMT), somatic cell nuclear transfer (SCNT)] have been recently introduced that enable transgenic animals to be produced more efficiently and more cheaply. These have been successfully applied to the development of several types of GM animals including cattle, sheep, pigs, chicken and fish. The potential benefits of GM animals include accelerated animal

Resveratrol, pterostilbene, and baicalein: plant-derived anti-biofilm agents

Microbial adhesion to surfaces and the subsequent biofilm formation may result in contamination in food industry and in healthcare-associated infections and may significantly affect postoperative care. Some plants produce substances with antioxidant and antimicrobial properties that are able to inhibit the growth of food-borne pathogens. The aim of our study was to evaluate antimicrobial and anti-biofilm effect of baicalein, resveratrol, and pterostilbene on Candida albicans, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. We determined the minimum inhibitory concentrations (MIC), the minimum adhesion inhibitory concentration (MAIC), and the minimum biofilm eradication concentration (MBEC) by crystal violet and XTT determination. Resveratrol and pterostilbene have been shown to inhibit the formation of biofilms as well as to disrupt preformed biofilms. Our results suggest that resveratrol and pterostilbene appear potentially very useful to control and inhibit biofilm contaminations by Candida albicans, Staphylococcus epidermidis, and Escherichia coli in the food industry.

Importance of microbial defence systems to bile salts and mechanisms of serum cholesterol reduction

An important feature of the intestinal microbiota, particularly in the case of administered probiotic microorganisms, is their resistance to conditions in the gastrointestinal tract, particularly tolerance to and growth in the presence of bile salts. Bacteria can use several defence mechanisms against bile, including special transport mechanisms, the synthesis of various types of surface proteins and fatty acids or the production of exopolysaccharides. The ability to enzymatically hydrolyse bile salts occurs in a variety of bacteria. Choloylglycine hydrolase (EC 3.5.1.24), a bile salt hydrolase, is a constitutive intracellular enzyme responsible for the hydrolysis of an amide bond between glycine or taurine and the steroid nucleus of bile acids. Its presence was demonstrated in specific microorganisms from several bacterial genera (Lactobacillus spp., Bifidobacterium spp., Clostridium spp., Bacteroides spp.). Occurrence and gene arrangement encoding this enzyme are highly variable in probiotic microorganisms. Bile salt hydrolase activity may provide the possibility to use the released amino acids by bacteria as sources of carbon and nitrogen, to facilitate detoxification of bile or to support the incorporation of cholesterol into the cell wall. Deconjugation of bile salts may be directly related to a lowering of serum cholesterol levels, from which conjugated bile salts are synthesized de novo. Furthermore, the ability of microorganisms to assimilate or to bind ingested cholesterol to the cell wall or to eliminate it by co-precipitation with released cholic acid was also documented. Some intestinal microflora produce cholesterol reductase that catalyses the conversion of cholesterol to insoluble coprostanol, which is subsequently excreted in faeces, thereby also reducing the amount of exogenous cholesterol.