Feasibility Study for the Potential Use of Biocatalytic Systems to Destroy Chlorofluorocarbons (CFCs)

ABSTRACT

In this review, we present the various microbial enzymatic systems involved in chlorocarbon biodegradation and evaluate their potential use as biocatalysts for the destruction of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons. Based on our present knowledge of the microbial metabolism of halogenated organic compounds, both anaerobic and aerobic processes could theoretically be used for the destruction of CFCs. The anaerobic processes result in the reductive dehalogenation of halogenated compounds. We describe the biological systems that were found to be involved in the reductive dehalogenation of halogenated hydrocarbons, present a number of hypotheses that have been proposed to explain this phenomenon, and discuss the potential use of these systems for the destruction of CFCs. The aerobic processes are based on the capacity of several large-spectrum activity mono- and dioxygenases that catalyze the initial oxidative step of aliphatic as well as aromatic compounds. In this case, the halogenated alkenes are converted to alkene epoxides that are quite unstable and break down to products that are readily metabolizable by other microorganisms. We discuss the potential use of this type of reaction for the destruction of CFCs and present approaches using genetically engineered microorganisms to more efficiently degrade these compounds.

KEY WORDS:

• reductive dehalogenation
• methane monooxygenase
• toluene dioxygenase
• freons
• ozone depletion substances
• biodegradation
• anaerobic process