ABSTRACT
Biodegradation is a process where the chemical structure of the substance is degraded, usually to carbon dioxide and water. Biotransformation is the metabolism of the substance without a significant change of its chemical nature. Biotransformation and biodegradation are used in environmental biotechnology for water and wastewater treatment, soil remediation, and exhaust gas purification. Co-metabolism is the transformation of an organic compound by microorganisms that are unable to use this compound as a source of energy or carbon but can degrade it due to similarity with the source of energy or carbon. Monosaccharides and storage polysaccharides, as well as proteins and nucleic acids, are degraded quickly, whereas cellulose and other structural polysaccharides are degraded slowly. Lipids, hydrocarbons, and lignin are degraded slowly under aerobic conditions. Phenols and aromatic acids can be degraded after the cleavage of the aromatic ring between the attached hydroxylic groups (ortho-cleavage) or in the position close to hydroxylic group (meta-cleavage). Chlorinated aliphatic and aromatic hydrocarbons are degraded slowly and only after replacement of the chlorine atom for the hydroxylic group. The gene(s) of specific enzyme(s) of biodegradation is (are) often located not in the bacterial chromosome but on a mobile genetic element such as a plasmid. A tutorial with solutions and a quiz bank are added to this chapter.
