Bioremediation of HMX-Contaminated Soil Using Soil Slurry Reactors

Soil in some parts of the Iowa Army Ammunition Plant in Burlington, Iowa, was contaminated with cyclotetramethyleneter-anitramine, commonly known as high melting explosive (HMX). A laboratory treat-ability study was conducted to find out the ability of the native soil bacteria present in the contaminated site to degrade HMX. The results indicated that the HMX can be removed effectively from soil by native soil bacteria through a co-metabolic process. Molasses, identified as an effective co-substrate, is inexpensive, and this factor makes the treatment system cost-effective. The successful operation of aerobic-anoxic soil slurry reactors in batch mode with HMX-contaminated soil showed that the technology can be scaled up for field demonstration. The HMX concentration in the contaminated soil was decreased by 97% in 4 months of reactor operation. The advantage of the slurry reactor is its simplicity of operation. The method needs only mixing and the addition of molasses as co-substrate.     

Process development of starch hydrolysis using mixing characteristics of Taylor vortices

In food industries, enzymatic starch hydrolysis is an important process that consists of two steps: gelatinization and saccharification. One of the major difficulties in designing the starch hydrolysis process is the sharp change in its rheological properties. In this study, Taylor–Couette flow reactor was applied to continuous starch hydrolysis process. The concentration of reducing sugar produced via enzymatic hydrolysis was evaluated by varying operational variables: rotational speed of the inner cylinder, axial velocity (reaction time), amount of enzyme, and initial starch content in the slurry. When Taylor vortices were formed in the annular space, efficient hydrolysis occurred because Taylor vortices improved the mixing of gelatinized starch with enzyme. Furthermore, a modified inner cylinder was proposed, and its mixing performance was numerically investigated. The modified inner cylinder showed higher potential for enhanced mixing of gelatinized starch and the enzyme than the conventional cylinder.     

Contamination of food by crude oil affects food selection and growth performance,but not appetite,in an Arctic fish,the polar cod (Boreogadus saida)

The polar cod (Boreogadus saida) is recognized as a key species in Arctic marine food webs and it may, therefore, be important for the transfer of xenobiotics from lower trophic levels to its main predators, birds and sea mammals. The present work examines the effects of foods contaminated with 200 or 400 ppm crude oil on food selection patterns and appetite-growth relationships in polar cod using X-radiography. It is shown that sexually mature polar cod consumed mixtures of uncontaminated and oil-contaminated foods, and did not show a reduced overall appetite as compared with fish provided with uncontaminated food only. Food selection was, however, influenced by both sex and individual appetite. Male fish selected uncontaminated food when appetite was low, whereas females ingested contaminated and uncontaminated foods equally, irrespective of appetite level. The ingestion of oil-contaminated food led to a significant depression in growth performance in both male and female fish. Food contaminated with oil at a concentration of 500 ppm was completely rejected by both sexes.     

Use of polymerase chain reaction for detection of Listeria monocytogenes in food.

A previously described polymerase chain reaction (PCR) assay (B. Furrer, U. Candrian, C. H?felein, and J. Lüthy, J. Appl. Bacteriol. 70:372-379, 1991) was used to analyze food for the presence of Listeria monocytogenes. Food samples were artificially contaminated to develop two procedures to detect the organism following enrichment steps. Procedure A was based on dilution of the enrichment broth followed by lysis of the bacteria and direct analysis of the lysate with PCR. With procedure A and artificially contaminated food samples, it was possible to detect fewer than 10 bacteria per 10 g of food. In procedure B, centrifugation was used to concentrate bacteria before lysis and PCR. With procedure A, 330 naturally contaminated food samples of several types were analyzed. Twenty samples were found to be positive for L. monocytogenes, which was in agreement with the classical culture technique. By using procedure B on a subset of 100 food samples, 14 were found to be positive by PCR whereas the classical culture method detected only 13. Analysis times, including enrichment steps, were 56 and 32 h with procedures A and B, respectively.     

Occurrence of fumonisins (B<Subscript>1</Subscript>, B<Subscript>2</Subscript>, B<Subscript>3</Subscript>) in maize-based food and feed samples from Indonesia

A survey to evaluate the contamination level of total fumonisins in maize-based foodstuffs, maize and feed from Indonesia is described. The analyses were carried out by enzyme-linked immunosorbent assay (ELISA). Samples were collected from local retail stores around Yogyakarta, Indonesia between February and May 2001. The 101 samples were classified into six categories, i.e. industrially-produced food (n=24), products of small food manufacturers (n=17), maize flour (n=4), maize for food (n=9), maize for feed (n17), and formulated feed (n30). Control of the method showed that the detection limit was 8.7 μg/kg and repeatability is shown by relative standard deviation (RSD) of analyses of contaminated maize (n=5) of 10 %. Results of analyses indicate that 80 samples analysed were contaminated over a large range from 10.0-3307 pg/kg, and the concentration of fumonisins depended on the type of sample. Of four samples of maize flour, none were contaminated (below detection limit). Of 24 samples of industrially produced food, 14 were contaminated in the range 22.8 - 105 μg/kg and 18 of 19 food samples from small manufacturers were contaminated ranging from 12.9 to 234 μg/kg. The highest contamination was observed in maize samples: six of ten samples of maize for food were contaminated between 68.0 - 2471 μg/kg and 16 of 17 samples for feed contained fumonisins over a large range from 17.6 to 3306 μg/kg.     

An in-use study of the relationship between bacterial contamination of food preparation surfaces and cleaning cloths

The relationship between bacterial contamination of food preparation surfaces and the cleaning cloths associated with these surfaces was investigated in a busy college kitchen. Cleaning cloths used in conjunction with detergent became heavily contaminated within hours of first use. Following 'cleaning' with these cloths with detergent, both surfaces and cloths were found to be more heavily contaminated and there was evidence of contamination transfer to and from cloths and surfaces. Following 'cleaning' with cloths impregnated with quaternary ammonium disinfectant, there was a significant reduction in contamination on both surfaces and cloths, together with a reduction in the numbers of enterobacteria and pseudomonads. The results suggest that significant improvements in kitchen hygiene could be achieved by ensuring that contaminated cloths are not used for food preparation activities.     

Potential of agricultural by-products in the bioremediation of fuel spills

Respirometer studies were used to determine the benefits of mixing soybean hulls with gravel contaminated with petroleum products. The aerobic conditions prevailing in the respirometer maintained significant microbiological activity. A reduction in petrochemical concentrations was detected, whether the contaminated gravel was treated with agricultural by-products or not, but at a slightly faster rate with the treatment. Received 6 November 1997/ Accepted in revised form 13 June 1998     

Stability of sterigmatocystin during the bread making process and its occurrence in bread from the Latvian market

Sterigmatocystin (STC) is a carcinogenic and mutagenic mycotoxin produced by fungi of many Aspergillus species. The aim of this research was to test the stability of STC during the bread making process and to check bread samples from the Latvian market for STC contamination, using a previously developed electrospray positive ionisation (ESI⁺) liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Wheat grain naturally contaminated with STC was used for bread baking. STC was found to be stable during the bread-making process. In the food survey 17% of the analysed breads were positive for STC, with concentration levels of 2-7 μg kg^-1. One out of six rye bread samples, one out of nine rye-wheat bread samples and three out of 14 wheat bread samples were contaminated with STC. Four out of five contaminated samples contained whole grains as the main ingredient. We conclude that whole grain bread may be a possible source of STC, although even STC-positive bread samples identified in this study contained quite low toxin levels.     

Uptake of organic mercury and selenium from food by nordic shrimp Pandalus borealis

Abstract

In an attempt to improve our understanding of the transfer process of organic mercury (mainly methyl mercury) from the prey to the consumer, the uptake of mercury in edible muscle of shrimps, Pandalus borealis, from contaminated mussels used as food supplies was studied. Shrimps bioaccumulated rapidly mercury in their abdominal muscle when submitted to a highly contaminated diet (6 μg Hg g^?1) but biomagnification was not observed and Hg concentration in shrimps never exceeded 1.8 μg g^?1. The assimilation efficiency during the uptake period was estimated to about 42% When shrimps received moderately contaminated diet (2.5–2.9 μg Hg g^?1), a two-stage bioaccumulation process was observed in which mercury concentration began to increase in shrimp muscle after 15 days of contaminated diet and at the end of the experiment it seemed to level off. This process can be represented by a two-compartment conceptual model in which mercury rs first eliminated and/or accumulated in the compartment 1 (digestive organs) and then transferred to the compartment 2 (abdominal muscle) following a mechanism and under conditions not yet clearly understood. The use of selenium biologically incorporated into the diet had no apparent effect on the uptake of mercury     

A novel real-time PCR-based method for the detection of Listeria monocytogenes in food

AIMS: A new real-time PCR-based method was developed for the detection of Listeria monocytogenes in food. METHODS AND RESULTS: A two-step enrichment involving a 24-h incubation in half-Fraser broth followed by a 6-h subculture in Fraser broth was used, followed by cell lysis and real-time PCR with primers and a TaqMan probe previously developed in our laboratory. When the method was evaluated with 144 naturally contaminated food samples, 44 were detected as positive by the PCR-based method and 42 by the standard method EN ISO 11290-1. With 61 food samples artificially contaminated at a level of 10(0) CFU per 25 g, 61 and 58 positive samples were detected by the respective methods. CONCLUSIONS: The developed real-time PCR-based method facilitated the detection of L. monocytogenes in food on the next day after the sample reception, with a reduction of false-positive results because of dead bacterial cells and false-negative results because of PCR inhibitors. SIGNIFICANCE AND IMPACT OF THE STUDY: The method can be used for L. monocytogenes detection in food as a faster alternative to current methods.     

A survey of fumonisins (B1, B2, B3) in Indonesian corn-based food and feed samples

In this paper a survey is described for determination of contamination level of fumonisins (B¹, B², B³) in Indonesian cornbased feed and food samples. The survey was conducted from February to May 2001. Foodstuffs, which are consumed directly such as snacks and other products, were investigated for fumonisin contamination. Of 105 food and feed samples purchased from local retail stores and local poultry shops around Yogyakarta, Java, Indonesia were analyzed using ELISA. Results indicate that 74.3% of samples analyzed were contaminated in a large range of 10.0 – 3307 μg/kg, and the concentration of fumonisins depends on the type of samples. Detection limit of the method used was 9 μg/kg.From eight food samples of maize flour, and corn-based beverages and cereals, none was contaminated (below detection limit). For food samples of industrial products (19 samples), 13 were contaminated in the range of 22.8 – 105 μg/kg and 19 of 20 samples from home made products were contaminated between 12.9 – 234 μg/kg. The food samples contaminated in highest level occurred in corn. Of ten samples, 6 were contaminated from 68.0 – 2471 μg/kg. For feed samples, 17 corn samples were evaluated. Of those samples, 16 contained in a large range of 17.6 – 3306 μg/kg.     

Use of a LightCycler gyrA mutation assay for identification of ciprofloxacin-resistant Campylobacter coli

An outbreak caused by dried processed squids contaminated with Salmonella Oranienburg occurred in Japan in 1999. Isolates obtained from the causative food were resistant to NaCl osmotic stress, but isolates from the patients were sensitive to NaCl. Although strains from both sources were almost identical in their virulence in mice, a NaCl-resistant strain from food (Sa9911T) became NaCl-sensitive after passage in mice and a NaCl-sensitive strain from one patient (Sa99004) retained NaCl sensitivity after such passage. When dried squid was contaminated experimentally with both strains during processing, only Sa9911T was recovered directly from the final product. Nevertheless, the viability of the Sa99004 cells was over 90% found by fluorescent staining. We suggested that Sa99004 might become viable but non-culturable (VNC) by NaCl stress. This hypothesis was confirmed by resuscitation by efficient enrichment. We concluded that VNC S. Oranienburg would be potentially dangerous contaminants of NaCl-preserved foods and that measures to ensure their detection should be taken at the time of food inspection.     

PCR detection of Listeria monocytogenes: a study of multiple factors affecting sensitivity

AIMS: To test, under comparable conditions, several parameters affecting sensitivity of PCR detection in order to establish a PCR procedure suitable for the routine detection of Listeria monocytogenes in food. METHODS AND RESULTS: Beef samples artificially inoculated were used to determine sensitivity of PCR detection under different parameters. As few as 1 CFU g(-1) were detected by DNA extraction using a DNeasy Tissue Kit (Qiagen GmhH, Hilden, Germany) of 1 ml aliquot and PCR amplification with primers directed to the hlyA gene. This PCR protocol was applied in 60 naturally contaminated foods, comparing two enrichment procedures with the traditional culture method. The highest number of positives was recorded by PCR following a 24-h pre-enrichment step at 30 degrees C and a 24-h enrichment step at 37 degrees C. Afterwards, it was applied in 217 naturally contaminated foods and 56 of them tested positive for L. monocytogenes in which only 17 tested positive using the culture method. CONCLUSIONS: The PCR procedure described has proved to be a rapid and sensitive method suitable for the routine analysis of different types of food. SIGNIFICANCE AND IMPACT OF THE STUDY: The method proposed for the detection of L. monocytogenes, has been validated in naturally contaminated food and is suitable to implement in the food industry.     

The interplay between nutrient balancing and toxin dilution in foraging by a generalist insect herbivore

Food mixing by herbivores is thought to balance nutrient intake and possibly dilute secondary metabolites characteristic of different host plant species. Most empirical work on insect herbivores has focused on nutrient balancing in laboratory settings. In this study, we characterize food mixing behaviour of the caterpillar Grammia geneura (Strecker) (Lepidoptera: Arctiidae) in nature and use the observed patterns to design ecologically relevant experiments that reveal the relative importance of these processes in food-switching behaviour. Our design involved both choice and no-choice experiments with chemically defined diets in which primary nutrients and secondary metabolites were manipulated in tandem. We analysed two stages in the process of food-switching behaviour: leaving food and accepting new food. In nature, an individual's rate of leaving host plants was positively associated with its probability of rejecting plant species most recently eaten, but not related to its probability of accepting different host plant species. Furthermore, an individual's leaving rate was negatively related to its average feeding bout duration. This relationship resulted partly from variation in the response of individuals to nutrient imbalance and partly from shortened feeding bouts prior to switching, suggesting that a decline in feeding excitation preceded searching for food that differed from that most recently eaten. Laboratory experiments with synthetic diets indicated the importance of secondary metabolites in the decline in feeding excitation prior to switching. Preference for new food depended strongly on secondary metabolites in a manner consistent with toxin dilution. This is the first experimental evidence for the process of toxin dilution in caterpillars, and for the combined influence of nutrients and secondary metabolites on their foraging patterns in nature. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Biodegradation of PCBs in two-phase partitioning bioreactors following solid extraction from soil

This article demonstrates the feasibility of a novel process concept for the remediation of PCB contaminated soil. The proposed process consists of PCB extraction from soil using solid polymer beads, followed by biodegradation of the extracted PCBs in a solid-liquid two-phase partitioning bioreactor (TPPB), where PCBs are delivered from the polymer beads to the degrading organisms. The commercially available thermoplastic polymer Hytrel was used to extract Aroclor 1242 from contaminated artificial soil in bench scale experiments. Initial PCB contamination levels of 100 and 1,000 mg kg(-1) could be reduced to 32% +/- 1 to 41% +/- 7 of the initial value after 48 h mixing in the presence of a mobilizing agent at polymer-to-soil ratios of 1% (w/w) and 10% (w/w). The decrease of detectable PCBs in the soil was consistent with an increase of PCBs in the polymer beads. It was further shown that Aroclor 1242 could be delivered to the PCB degrading organism Burkholderia xenovorans LB400 in a solid-liquid TPPB via Hytrel beads. A total of 70 mg Aroclor 1242 could be degraded in a 1 L solid-liquid TPPB within 80 h of operation.     

Gastric pH Distribution and Mixing of Soft and Rigid Food Particles in the Stomach using a Dual-Marker Technique

Mixing of a particle-laden material during peristaltic flow in the stomach has not been quantified in vivo. Gastric mixing plays a key role in the digestion process; it determines the availability of acid and enzymes to individual food particles and controls the length of time particles will spend in the antral region, where they are subjected to mechanical breakdown from antral contraction waves. Solid particle mixing has been quantified using a dual-indigestible marker technique (TiO₂ and Cr₂O₃) in soft (cooked brown and white rice) and rigid (raw and roasted almonds) particle meals fed to growing pigs. All meals consisted of two portions. Each portion was separately marked by one of the two indigestible markers, and the portions were sequentially fed to the pigs. At time periods ranging from 20 to 720 min after completion of the meal, ten intragastric chyme samples were taken from each pig to determine the marker concentration and pH value. Gastric pH was not homogeneous throughout the stomach and varied over time, with differences observed between soft and rigid meals (p?<?0.0001). The total percentage of each meal that was mixed was calculated using a statistically-based mixing index (M). White rice had the greatest amount of mixing, becoming 94 % mixed after 480 min of digestion compared to 72 % mixing for brown rice. Rigid particles underwent a slower mixing process and only arrived at 65 and 71 % mixing after 720 min for raw and roasted almonds, respectively. Meal composition plays a role in the overall meal mixing during gastric digestion.     

Observations of boll weevil midgut when fed natural food or on bacterially contaminated artificial diet

Boll weevils fed natural food had normal midgut morphology, but weevils fed bacterially contaminated artificial diet had deteriorated midguts which became progressively less functional with continued feeding on the diet. Reversal of the conditions occurred when the weevils were returned to natural food. This recovery did not take place, however, if the deterioration was too advanced. All strains of boll weevils had similar midgut responses. Cellular destruction in the midgut and loss of tissue function led to typical symptoms of starvation and desiccation during the first 10 days of adult life. Continued feeding upon contaminated food resulted in premature death. These observations show the importance of sanitation in mass-rearing procedures. It also may provide an explanation for subnormal boll weevil quality as reported by other authors who measured longevity, pheromone, and fatty acid production.     

The effectiveness of hygiene procedures for prevention of cross-contamination from chicken carcases in the domestic kitchen

Thirteen sites in each of 60 domestic kitchens were examined for Salmonella and Campylobacter spp. following the preparation of a chicken for cooking and the application of different hygiene regimes. During food preparation bacteria became widely disseminated to hand and food contact surfaces. Where cleaning was carried out with detergent and hot water using a prescribed routine there was no significant decrease in the frequency of contaminated surfaces. Where hypochlorite was used in addition, a significant reduction in the number of contaminated sites was observed. The study suggests that there is a need to better understand and promote effective hygiene procedures for the domestic kitchen.     

The chemical form of trivalent chromium in xylem sap of maize (Zea mays L.)

Abstract

The toxicity, mobility and bioavailability of Cr, a versatile industrial metal and a contaminant, depends on its chemical form, viz: Cr(lll) and Cr(VI). It may enter humans through plants grown on contaminated soil or irrigated by contaminated water. The phytoavailability and transfer through agricultural food chains requires an understanding of mechanisms of Cr uptake and translocation by plants. Xylem sap transports both nutrient and non-nutrient ions after absorption by roots to aerial parts of the plant. lt transports cations by complexation with organic ligands. Trivalent chromium, though prone to hydrolysis, also complexes O donor ligands. The chemical form in which Cr(lll) is transported by xylem sap was investigated. ln vitro studies were performed by mixing the xylem sap of maize plants at three stages of plant growth with radiotagged Cr(III). The speciation change was investigated after 10 days and 30 days by anion and cation exchange elution chromatography. The elution curves were compared with those of pure Cr(III) and Cr(III) complexes of different synthetic acids. Complexation of Cr(III) with ligands of xylem sap especially with carboxylates was evident. Cationic Cr(III) was vitally being transported as anionic organic complex species. The major species seemed to be that of Cr(III)-citrate. Citric acid was the major complexing acid of xylem sap as determined by HPLC. These mobile and soluble complexes may get immobilized and stored in leaves and other edible plant parts. This may also be a mechanism used by plants for detoxification of toxic Cr(VI) which may become reduced and then complexed.     

Salmonella-TEK, a rapid screening method for Salmonella species in food.

A micro-enzyme-linked immunosorbent assay (micro-ELISA) using the Salmonella-TEK screen kit was tested for the detection of Salmonella spp. in pure cultures as well as in 30 artificially contaminated food samples and in 45 naturally contaminated food samples. Different raw, fleshy foods and processed foods were used as test products. The artificially contaminated minced meat samples were preenriched in buffered peptone water, and after incubation, different selective enrichment broths were tested. The micro-ELISA optical density values after enrichment and isolation of the different broths were very analogous. The quickest method to detect Salmonella spp. in different foods is to enrich them with Salmosyst broth, which reduces the total analysis time to 31 h. The Salmonella-TEK kit for Salmonella spp. provides a promising test for the detection of Salmonella antigens in food even when they are present at a low concentration (1 to 5 CFU/25 g). The cross-reaction of the anti-Salmonella antibodies, especially to other gram-negative bacteria, is nil.