Extremophilic and Extremotolerant Nitrile-Hydrolyzing Microorganisms: Distribution and Biotechnological Potential (Review)

— The ubiquity of nitriles today and, according to one hypothesis, their presence as one of the basic substrates during the emergence of life in the early stages of Earth’s history, has led to the emergence of microorganisms producing nitrile-hydrolyzing enzymes among a wide variety of phylogenetic and ecological groups, including extremophilic prokaryotes and a small number of unicellular eukaryotic organisms. This review summarizes information on nitrile-degrading microorganisms isolated from extreme biotopes that differ in origin and type of aggressive environmental conditions. Nitrile-hydrolyzing enzymes, their substrate preferences, whole-cell culture conditions, and optimal environmental parameters for nitrile-hydrolyzing activity are characterized. The main areas of study and application of nitrile-utilizing microorganisms are biotechnological (use as biocatalysts for various chemical processes and the biodegradation of toxic cyanides and nitriles), ecological (clarification of the role of nitriles in the nitrogen cycle), and evolutionary (molecular clock dating). Particular attention is given to the role of nitriles in the natural nitrogen cycle.