Microbial Action

Many biopolymers are designed to be discarded in landfills, composts, or soil. The materials will be broken down, provided that the required microorganisms are present. Normal soil bacteria and water are generally all that is required, adding to the appeal of microbially reduced plastics. Polymers that are based on naturally 

Another approach to microbial degradation of biopolymers involves growing microorganisms for the specific purpose of digesting polymer materials. This is a more intensive process that ultimately costs more. Although this method reduces the volume of waste, it does not aid in the preservation of non-renewable resources [Ashwin, 2011). 

Some biodegradable polymer materials experience a rapid dissolution when exposed to particular [chemically based) aqueous solutions. Biopolymer materials that disintegrate upon exposure to aqueous solutions are desirable for the disposal and transport of biohazards and medical wastes. Industrial washing machines are designed to dissolve and wash away the aqueous solutions 

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Xanthan Gum. As a result of a project to transform agriculturally derived products into industrially usefiil products by microbial action, the Northern Regional Research Laboratories of the USDA showed that the bacterium TCanthomonas campestris - noduces a polysaccharide with industrially usefiil properties (77). Extensive research was carried out on this interesting polysaccharide in several industrial laboratories during the eady 1960s, culminating in commercial production in 1964. 

CDU in pure form is a white powder. It is made slowly available to the soil solution by nature of its limited solubihty in water. Once in the soil solution, nitrogen from CDU is made available to the plant through a combination of hydrolysis and microbial decomposition. As with any CRE which is dependent on microbial action, the mineralization of CDU is temperature dependent. Product particle size has a significant effect on CDU nitrogen release rate. Smaller particles mineralize more rapidly because of the larger surface contact with the soil solution and the microbial environment. The rate of nitrogen release is also affected by pH because CDU degrades more rapidly in acidic soils. 

Microbesuseenzymesascatalyststomakethedesiredorbeneficialreactiontakeplace, and typically under mild conditions. Brewing of beer and fermentation of fruit and veg-etablemasshighinstarchestoproduceconsumableethanolaretheoldestandmostfamiliar instances of using microbial action to fulfill a desired end. But now much more has been demonstrated,rangingfromtheproductionofessentialhumanhormonestothesynthesisof special tychemicals. 

Some simple foods can be preservatives in their own right. Honey, salt, sugar, lactic acid, and vinegar are all examples of foods that inhibit microbial action. Some health professionals recommend consuming phytoestrogens from foods such as soybeans to achieve various health benefits. The phytoestrogens in the paraben family, found in blueberries, kill molds and fungi and are often added to food as preservatives. 

Finally, it is stimulating to read the article by Little and Wagner because of the prominence attached to microbial action in the electrochemistry of the 1990s and because it has hitherto been difficult to find an electrochemically oriented presentation of this topic. 

The specific microbes used depends on many factors, for example, the particular formation involved, the specific hydrocarbons in the formation, and the desired microbial action on these formation hydrocarbons. The microbes may be aerobic or anaerobic and may or may not require one or more additional nutrients (e.g., naturally ocurring or injected) to be included in the formation. Highly mobile microbes, such as flagellated or ciliated bacilli, are useful. The microbes are sized so that they are mobile in the connate water of the formation [966]. 

The genus Thiobacillus, especially the species T. denitrificans catalyzed the oxidation reactions of hydrogen sulfide yielding soluble hydrosulfide compounds, elemental sulfur, and sulfuric acid. Carbonyl sulfide and carbon disulfide are converted to hydrogen sulfide by hydrolysis. Additionally, they are oxidized to SOx and sulfates via microbial action. The reported oxidation reactions of thiosulfate using nitrate as electron acceptor are ... 

Root exudation and microbial action produce organic compounds with a range of composition and molecular weights. These compounds interact with the mineral particles, which also vary in size, shape, ciystallinity, and electric charge (Emerson et al. 1986). Interactions between soil mineral particles, organic matter and microbes can occur at many different size scales, because these materials have a large size range in soils (Fig. 7). 

Acidity/ Alkalinity Refrigeration Gains or losses of C02 affect the result. Microbial action can affect this, should be one of the first analyses of the sample. 

Time from autopsy to sample analysis, wherein cyanide concentrations may increase due to microbial action... 

We have developed and tested a metabolism system and regimen which allows collection of data comparable to those from terrestrial animals. The key to our experiments is a metabolism chamber, described previously Cl3, 14) CFig. 1), which can be operated in either the static or flow-through mode. Briefly, individuals or groups of animals are held at constant temperature in the jacketed glass chamber (A), on a stainless steel screen (B), while pure water or test solution is passed over them (or held under static conditions). Solid wastes are separated in a jacketed container (C) held near 0°C to minimize microbial action, and the effluent containing dissolved metabolites is passed onto a column of nonionic macroreticular adsoprtion resin where organic solutes are adsorbed from solution (D). 

The isotope geochemistry of Se is complex because it involves several inorganic oxidation states and organic forms, kinetic isotope effects, and microbial action (Fig. 3). Fortunately,... 

Mercury occurs in soils predominantly in the +2 oxidation state. Elemental Hg in the atmosphere is oxidized to Hg + and deposited in rainfall. It is a strong chalcophile and under anaerobic conditions forms the extremely insoluble sulfide cinnabar (HgS, pK = 52.7). Nonetheless it is not entirely immobilized under anaerobic conditions because it is reduced to volatile Hg° or methylated to volatile methyl mercury compounds by microbial action, and so returned to the atmosphere. The methylation is mediated by various bacteria, especially methanogens, through the reactions ... 

During microbial action, kinetic isotope fractionations on the organic material by methanogenic bacteria result in methane that is highly depleted in typically with 5 C-values between -110 and -50%c (Schoell 1984, 1988 Rice and Claypool 1981 Whiticar et al. 1986). In marine sediments, methane formed by CO2 reduction is often more depleted in than methane formed by acetate fermentation in freshwater sediments. Thus, typical ranges for marine sediments are between -110 and -60%c, while those for methane from freshwater sediments are from -65 to -50%c (Whiticar et al. 1986 Whiticar 1999). 

Schroten, H. (2001). Chemistry of milk mucins and their anti-microbial action. Adv. Nutr. Res. 10, 231-245. 

Nickel removed by coprecipitation can be remobilized by microbial action under anaerobic conditions (Francis and Dodge 1990). Remobilization results Ifom enzymatic reductive dissolution of iron with subsequent release of coprecipitated metals. A lowering of pH as a result of enzymatic reactions may indirectly enhance the dissolution of nickel. Experiments using mixed precipitates with goethite... 

According to Product Services Company, treatment will be most efficient at temperatures between 40 and 120°E. Pesticides, degreasing agents, and heavy metals may have an adverse impact on the microbial action. The pH should be between 4.5 and 9.5, with an optimum of 7.0. Moisture content should be maintained at 30% throughout the remediation. 

Since the middle of the nineteenth century we have introduced increasing quantities of complex, man-made (anthropogenic) chemical compounds into the natural enviromnent. Many of these substances are recycled by microbial action, whilst others are poorly... 

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