Microbial Isobutyronitrile Utilization under Haloalkaline Conditions

Abstract

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.

Bacterial diversity and activity along a salinity gradient in soda lakes of the Kulunda Steppe (Altai, Russia)

“…Strain ANLiso2 was enriched and isolated from Kulunda Steppe soda lake sediments using isobutyronitrile as the only substrate. It is specialized in the degradation of C3-C6 aliphatic nitriles (Sorokin et al 2007b). …”

Nitriliruptor alkaliphilus gen. nov., sp. nov., a deep-lineage haloalkaliphilic actinobacterium from soda lakes capable of growth on aliphatic nitriles, and proposal of Nitriliruptoraceae fam. nov. and Nitriliruptorales ord. nov.

“…Furthermore, we also demonstrated the possibility of biodegradation of more complex nitriles, such as isobutyronitrile (iBN) [(CH 3 ) 2 CHCN], by two haloalkaliphilic consortia, enriched from soda lakes and soda soils (Sorokin et al, 2007b). In the soda lake consortium, the key reaction in iBN hydrolysis was performed by the novel haloalkaliphilic actinobacterium described in the present paper.…”

“…The spirillum was isolated from the mixed culture by using isobutyroamide, which is the first product of iBN hydrolysis in the nitrile hydratase/amidase pathway. The organism was identified as a member of the genus Marinospirillum in the class Gammaproteobacteria (Sorokin et al, 2007b). Further experiments showed that this bacterium played the role of scavenging of iBN hydrolysis products released by the rod-shaped phenotype.…”

“…We recently described the first example of a bacterium from soda lake sediments, Natronocella acetinitrilica, capable of growth with acetonitrile and propionitrile as carbon, energy and nitrogen source at haloalkaline conditions (Sorokin et al, 2007a). Furthermore, we also demonstrated the possibility of biodegradation of more complex nitriles, such as isobutyronitrile (iBN) [(CH 3 ) 2 CHCN], by two haloalkaliphilic consortia, enriched from soda lakes and soda soils (Sorokin et al, 2007b).…”

“…The isolation of an iBN-degrading consortium from soda lake sediments at pH 10 and the growth and metabolic properties of its members have been described previously (Sorokin et al, 2007b). A stable co-culture enriched from soda lake sediments capable of complete utilization of iBN at pH 10 and 0.6 M total Na + consisted of a motile spirillum as the dominant morphotype and short, nonmotile rods.…”