Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides: 2. Field Research on Bioremediation of Metals and Radionuclides

Bioremediation of metals and radionuclides has had many field tests, demonstrations, and full-scale implementations in recent years. Field research in this area has occurred for many different metals and radionuclides using a wide array of strategies. These strategies can be generally characterized in six major categories: biotransformation, bioaccumulation/bisorption, biodegradation of chelators, volatilization, treatment trains, and natural attenuation. For all field applications there are a number of critical biogeochemical issues that most be addressed for the successful field application. Monitoring and characterization parameters that are enabling to bioremediation of metals and radionuclides are presented here. For each of the strategies a case study is presented to demonstrate a field application that uses this strategy.     

Detection of Staphylococcal Enterotoxin in Foods

A short procedure for the extraction of staphylococcal enterotoxins from food materials has been developed. The procedure involves extraction of the food at pH 4.5, centrifugation, extraction of the supernatant with CHCl(3) (pH 7.5), extraction of the enterotoxin from the water layer with CG-50 ion exchange resin (pH 5.4 to 5.9), and treatment of the eluate with agar and concentration with Carbowax 20-M. The concentrate was extracted with CHCl(3), and the water layer was lyophilized. The dried material was dissolved in a 1% trypsin solution and placed on microslides, which were incubated 24 h at 37 C. The time required for enterotoxin analysis was 3 days with microslides and 1 day with the reversed passive hemagglutination technique.     

Invited Review Free Radicals in Foods

During the last decade increasing attention has been given to the role of free radicals in biological oxidations. The subject has been of increasing interest to both the food scientist and the physiologist. Free radical scavengers in the form of both indigenous and added antioxidants are necessary for the successful preservation of food; free radicals are increasingly being implicated in the onset of, among others, ischaemic heart disease and for protection against these diseases it is suggested that the dietary intake of the antioxidant vitamins should be increased especially for diets high in polyunsaturated fats. ^1,2 Convenience and snack foods which absorb substantial amounts of frying oils are being increasingly consumed. Since poly-unsaturated fatty acids are particularly susceptible to oxidation by free radicals during the storage, cooking and frying of foods, the potential risk of exposure to lipid degradation products' is likely to have increased. In foods the non-enzymic and lipoxygenase catalysed oxidation of polyunsaturated fatty acids, β-carotene and vitamin A can result in the loss of essential nutrients and the development of off-flavours.     

Enumeration of Bacillus cereus in Foods

For the enumeration of vegetative cells and spores of Bacillus cereus in foods, a mannitol-egg yolk-phenol red-agar has been developed which exploits the failure of B. cereus to dissimilate mannitol, and the ability of most strains to produce phospholipase C. When a high degree of selectivity was required, polymyxin B sulfate in a concentration of 10 ppm appeared to be the most effective selective additive. Useful characteristics for the identification of presumptive isolates of B. cereus were found to be: morphology, dissimilation of glucose mostly to acetyl methyl carbinol under anaerobic conditions, hydrolysis of starch and gelatin, reduction of nitrate, and growth on 0.25% chloral hydrate agar.     

Quantitation of Clostridium perfringens in Foods

A procedure is described for identifying and enumerating Clostridium perfringens in foods by means of a simplified agar plating method, followed by confirmation of black colonies in tubes of motility-nitrate medium and sporulation broth. The test is routinely completed within 48 hr. Under experimental conditions, the procedure has been used to quantitatively recover various levels of C. perfringens contamination in a variety of foods and has recovered as few as ten C. perfringens per g without interference from food constituents and associated flora. Under practical conditions of field application, the method has been used to investigate five food-poisoning outbreaks, and C. perfringens was implicated as the etiological agent in two of these outbreaks.     

Radiation Chemistry of Foods

Reaction rates of the extracts from foods and biological tissues with hydrated electrons were measured by using competition with N₂O. Water and 3% Na₂S0₄ aqueous extracts of pork and water extract of onion gave results which conformed to the simple relationship of competition. An addition test of the onion with acetone and nitrate suggested that their reactivities were simply additive, but the additive effect of cysteine was complicated.     

Radiation Chemistry of Foods

When 10^?3m cysteine solution was irradiated in the presence of glucose at the concentration of ten-fold of cysteine, the G-values of products produced from cysteine were similar to those from 10^?3m cysteine solution. On the other hand, the yield of carbonyl compound from glucose was suppressed completely by interaction between cysteine and radicals which are secondarily produced from glucose.

Methionine could not suppress the yield of carbonyl compound from glucose, and, G-values of products from methionine varied in comparison with those from solution containing methionine only.

From the results using scavenger, it was concluded that oxidation to methionine sulfoxide and cleavage to α-aminobutyric acid was caused by OH and attack, respectively.     

Foods and liver health

Chronic liver damage is a worldwide common pathology, characterised by an inflammatory and fibrotic process that leads to a progressive evolution from chronic hepatitis to cirrhosis and hepatocellular carcinoma (HCC). A major role for fats and oxidative stress has been recently demonstrated in the pathogenesis of liver diseases. In the clinical practice, dietary recommendations in the management of chronic diseases often rely on denying patients certain foods, which results in a severe reduction of quality of life. In this paper a new perspective based on the development of Food intended for Specific Medical Purposes (FSMP) containing highly bioavailable antioxidant compounds or polyunsaturated-fatty acids, has been highlighted as a tool for preventive and curative medicine, to be associated to pharmacological treatments.     

Radiation Chemistry of Foods

An intermediate radical, ?H₂OH, was produced in aqueous methanol solution containing nitrous oxide by γ-irradiation. Yields of ethylene glycol and formaldehyde, the major and the minor product from ?H₂OH, respectively, changed on the addition of some solutes. Cysteine lowered the both product yields to zero even at a low concentration of 5 × 10^?5m. Oxygen of low concentrations (2.5~7.5 × 10^?5 m) changed effectively the major product from ethylene glycol to formaldehyde. k _(CySH+?H2OH)/k_(O2+?H2OH) was calculated as 0.5.

Ascorbic acid (5 × 10^?5 m) lowered ethylene glycol yield to 48%, cystine (10^?3m) to 15%, methionine (10^?3m) to 31%, histidine (10^?3m) to 42%, tryptophan (10^?3m) 46%, tyrosine (10^?3m) to 77%, phenylalanine (10^?3m) to 73%, hypoxanthine (10^?3m) to 37%, adenine (10^?3m) to 52%, uracil (10^?3m) to 20%, thymine (10^?3m) to 10%, cytosine (10^?3 m) to 49%, rutin (10^?3m) to 23%, pyrogallol (10^?3m) to 41%, and gallic acid (10^?3m) to 78% of the control. These results suggest that the reactions of the secondary radicals such as ?H₂OH perform an important role in material change of foods irradiated with γ rays.     

Radiation Chemistry of Foods

In food irradiation, water-soluble food constituents undergo the attack of ${\text{e}}_{\text{aq}}^{?}$ and OH at the neutral region.

Reaction rate constants of some food constituents with ${\text{e}}_{\text{aq}}^{?}$ and OH were measured by competition methods using nitrous oxide and ³H-formate as competitors, respectively. High selectivity was observed among the reactions with ${\text{e}}_{\text{aq}}^{?}$ and the ${\text{e}}_{\text{aq}}^{?}$-reaction rate constants are 10¹⁰ M^?1 sec^?1 (cysteine), 10⁹ M^?1 sec^?1 (methionine, ascorbic acid, and histidine), and much smaller (sugars, and the other types of amino acids). The OH-reaction rate constants range from 10⁹ M^?1 sec^?1 (cysteine, histidine, methionine, aromatic amino acids, and ascorbic acid) to 10⁸ M^?1 sec^?1 (sugars and the other amino acids), indicating that the reactions with OH are less selective. Selective destructions of cysteine and ascorbic acid in food irradiation may be partly ascribed to their selective reactivities with some less reactive species which are produced by reactions of ${\text{e}}_{\text{aq}}^{?}$ or OH with oxygen or the other constituents as well as their higher reactivity with ${\text{e}}_{\text{aq}}^{?}$.     

Incidence of Clostridium perfringens in American Foods

Food samples were examined for the presence of Clostridium perfringens. A medium described by Mossel and later modified by Angelotti et al. was used for the detection and enumeration of C. perfringens. The incidence of C. perfringens observed in the foods examined was 6.1%. C. perfringens was recovered from 2.7% of the commercially prepared frozen foods, 3.8% of fruits and vegetables, 5.0% of spices, 1.8% of home-prepared foods, and 16.4% of raw meat, poultry, and fish.