In Situ Biodegredation
Melethia Crusenberry, Lou Ann Johnson, Amber Williams

Introduction

The terms bioremediation and biodegradation are sometimes erroneously treated a s being synonymous, however two distinct concepts are involved. Environmental bioremediation refers to a process of environmental improvement, in which biological organisms or products play a key role. Biodegradation specifically refers to chemical breakdown or mineralization of materials (not necessarily waste) facilitated by biological organisms or products. The result of this action may or may not be judged to be remediative, although biodegradation of waste often leads to bioremediation.

Many microorganisms can adapt their metabolic processes to make use of certain environmental pollutants as food sources. Thus, the microbes bioremediate the environment as they biodegrade the pollutants to obtain energy. As alluded to above, biodegradation of organic chemicals is accomplished enzymatically. Metabolic enzymes are proteins that catalyze specific degradation reactions of organic molecules and that usually display high affinity for certain substrates. By this process, organic wastes along with a few inorganics may be adsorbed by the microbe and broken down internally or wastes may be degraded externally by secreted enzymes, after which the metabolites are absorbed and utilized. Alternatively, microbial metabolic enzymes produced for breaking down normal food sources, may fortuitoulsy degrade certain wastes that are present as well. This process, termed “co-metabolism” obviously requires an ample supply of the preferred food substrate and also requires that the degrading enzymes come into contact with the waste adsorption or by enzyme secretion. Either direct metabolism or co-metabolism can be enhanced in rate and extent over that which availability of food and/or growth limiting nutrients. The basic information required to enhance natural biodegradative processes is knowledge of the microorganisms present in a given site and the food substrates they prefer to use.

The objective of bioremediation is to detoxify environmental contaminants constructively and harmlessly. With biodegradation it is possible for pollutant mixtures to be metabolized into more harmful mixtures by biological action and even relatively harmless wastes can cause environmental problems if production rates exceed the capacity of natural cycles of breakdown and renewal. Therefore the occurrence of biodegradation, in and of itself, does not necessarily constitute bioremediation.

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