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Environmental fate & pathways

Biodegradation in soil

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Jensen isolated micro-organisms from soil that are capable of utilizing monochloroacetic acid (MCA) as sole carbon and energy source for growth. The bacteria isolated were tentatively classified as Pseudomonas sp. These organisms are able to grow slowly on a basal medium plus MCA (0.05 M). The addition of a small amount of yeast extract resulted in rapid growth of the bacteria and simultaneous removal of MCA within three weeks. Another Pseudomonas sp. was grown in a continuous culture with MCA as growth limiting substrate. The growth rate in this culture reached 0.18 hours. Some halogenated aliphatic acids are used as herbicides and pesticides. Bacteria, capable of growing on these compounds are also able to metabolize MCA. For example, bacteria grown on Dalapon (2.2, dichloropropionic acid) or monochloropropionic acid are able to dehalogenize MCA since the enzymes induced by the growth substrate are also able of catalyzing the dehalogenation of MCA. The possession of enzymes known as dehalogenases enable micro-organisms to utilize halogenated alkanoic acid as carbon and energy sources. These dehalogenases catalyse the hydrolytic removal of chlorine from MCA yielding hydroxyacetic acid. The enzymes have been characterized by two types: a haloalkanoic acid dehalogenase and a halido hydrolase. Both enzymes are capable of dehalogenating MCA.

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