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Applied and Environmental Microbiology, September 2007, p. 5574-5579, Vol. 73, No. 17
0099-2240/07/$08.00+0     doi:10.1128/AEM.00342-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Microbial Isobutyronitrile Utilization under Haloalkaline Conditions

Winogradsky Institute of Microbiology, Russian Academy of Sciences, 117811 Moscow, Russia,¹ Environmental Biotechnology, Department of Biotechnology, Delft University of Technology, Delft, The Netherlands,² Biocatalysis and Organic Chemistry, Department of Biotechnology, Delft University of Technology, Delft, The Netherlands³

Received 12 February 2007/ Accepted 26 June 2007

The utilization of isobutyronitrile (iBN) as a C and N source under haloalkaline conditions by microbial communities from soda lake sediments and soda soils was studied. In both cases, a consortium consisting of two different bacterial species capable of the complete degradation and utilization of iBN at pH 10 was selected. The soda lake sediment consortium consisted of a new actinobacterium and a gammaproteobacterium from the genus Marinospirillum. The former was capable of fast hydrolysis of aliphatic nitriles to the corresponding amides and much-slower further hydrolysis of the amides to carboxylic acids. Its partner cannot hydrolyze nitriles but grew rapidly on amides and carboxylic acids, thus acting as a scavenger of products released by the actinobacterium. The soda soil consortium consisted of two Bacillus species (RNA group 1). One of them initiated nitrile hydrolysis, and the other utilized the hydrolysis products isobutyroamide (iBA) and isobutyrate (iB). In contrast to the actinobacterium, the nitrile-hydrolyzing soil Bacillus grew rapidly with hydrolysis products, but it was dependent on vitamins most probably supplied by its product-utilizing partner. All four bacterial strains isolated were moderately salt-tolerant alkaliphiles with a pH range for growth from pH 7.0 to 8.5 up to 10.3 to 10.5. However, both their nitrile hydratase and amidase activities had a near-neutral pH optimum, indicating an intracellular localization of these enzymes. Despite this fact, the study demonstrated a possibility of whole-cell biocatalytic hydrolysis of various nitriles at haloalkaline conditions.

Published ahead of print on 20 July 2007.