Natural Biodegradation

In some undisturbed subsurface systems, an equilibrium is established. Bacteria have acclimated to food sources, water availability, and electron acceptor types. The number and variety of microbial cells are balanced in this system. If the system is aerobic, the microbial activity continues at the rate of oxygen resupply. If the system is anaerobic, the rate of activity cannot exceed the accessibility of alternate electron acceptors. Generally, the subsurface (lower than the plant root zone) is relatively deficient in available carbon and electron acceptors. Under these normal semi-equilibrium conditions, a soil or aquifer system can consume organic materials within a reasonable range. When a chemical release is introduced into a well-established soil system, the system must change to react to this new energy source. The bacterial balance readjusts, in an effort to acclimate to the new carbon source. 

It was determined that rainwater infiltration from a fertilized wheat field over-lying the aquifer provided sufficient excess nitrogen and phosphorus to support 

FIGURE 13.7 Schematic cross sections of enhanced biorestoration of unconfined aquifers. 

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Since the purpose of this book is to describe applications of biodegradable polymers to drug delivery systems, particularly from the perspective of the materials employed, the approach taken in this chapter has been to focus on the natural biodegradable polymers which have been used most extensively as matrices for the delivery of drugs. Consideration was also given to the fact that collagen has not been the subject of any recent reviews. 

Typically, only those sites that have aerobic conditions in the contaminated zone because of shallow water tables and high rates of groundwater recharge have achieved significant natural biodegradation of MTBE and other oxygenates.65... 

Biodegradable polymers can be categorized into natural and synthetic polymers. The typical examples of natural biodegradable polymers are proteins,... 

The joint result of these three factors was that, by the 1960s, Americans had adopted an attitude about solid wastes quite different from that of their 1900 forebears. They were consuming a much larger volume of materials, most of which were not naturally biodegradable, that were simply being dumped in the most convenient locations in open dumps, landfills, large lakes, or the oceans. 

Biosurfactants are natural, biodegradable surfactants synthesized by certain strains of bacteria,... 

Because biosurfactants are natural, biodegradable products, they are an attractive alternative to synthetic surfactants, particularly for in situ remediation. Biosurfactants are also potentially useful agents for oil spill remediation, where they can be used to disperse pollutants that remain in the water or have washed up on land. 

Increases the natural biodegradation rate and decreases cleanup time. 

Petro-Green, Inc., ADP-7 is a biodegradable, water-soluble, nonionic/anionic liquid surfactant concentrate that emulsifies hydrocarbons, makes them water-wet, and allows natural processes to biodegrade them in situ. Once it is an emulsion, the hydrocarbons are no longer flammable or odoriferous. ADP-7 promotes the natural biodegradation processes. 

The progress made using the methods described in this report has opened up a number of opportunities. There are consumer and health pressures to reduce the consumption of synthetic emulsifiers used in processed foods. Therefore, a need exists to identify alternative natural replacement emulsifiers. One approach is to develop natural , biodegradable emulsifiers through biosynthetic routes using enzymes. Alternatively, more widespread use of proteins as emulsifiers would be an option if their functional properties were more... 

Vorhies, J.S., and Nemunaitis, J.J. (2008) Synthetic vs. natural/biodegradable polymers for delivery of shRNA based cancer therapies, in Macromolecular drag delivery (Belting, M., ed.), Humana Press, pp. 11-29. 

Synthetic vs. Natural/Biodegradable Polymers for Delivery of shRNA-Based Cancer Therapies... 

Key Players in Two Categories of Polymeric Non-viral Delivery Vehicle Systems Synthetic Polymers and Natural/Biodegradable Polymers... 

Natural/Biodegradable Polymeric Delivery Systems 5.1. Collagen... 

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