Characterization of Novel Alkaliphilic Isolate of <i>Bacillus mannanilyticus</i>, Strain IB-OR17, Displaying Chitinolytic and Antifungal Activities

Abstract

The novel alkaliphilic strain, designated as Bacillus sp. IB-OR17 and isolated from soda lake sediments, was identified and characterized. Isolated strain demonstrated slight antifungal activity against some plant pathogen fungi that are capable to grow under alkaline conditions. Based on its morphological, physiological and biochemical characteristics as well as on 16S rRNA gene analysis data, Bacillus sp. IB-OR17 were related to alkaliphilic species B. mannanilyticus . Such as type species, Bacillus sp. IB-OR17 produced extracellular β -mannanase but additionally it displayed also chitinolytic activity which is a new property reported for this species. Bacillus sp. IB-OR17 grew in pH range 8.0 - 11.0 with maximal intensity under 9.0 - 10.0 but not showed halophilic properties (growth limit under NaCl concentrations < 5%). Maximal production of chitinase is observed at the same pH interval after 96 h of submerged cultivation of the strain. Bacillus sp. IB-OR17 produced chitinase(s) in presence of colloidal chitin as main carbon source and sodium carbonate (0.25% - 1.0%) demonstrating high enzyme yield under enough low concentrations of the substrate (0.20%). Unlike chitinase, β -mannanase was constitutively produced by Bacillus sp. IB- OR17 in presence of various substrates including crab shell chitin. Probable involvement of the enzymes in antifungal activity of Bacillus sp. IB-OR17 is discussed shortly in terms of further researches and application of this strain.