Isolation and identification of an inulinase-producing strain and the optimization of its fermentation condition

Abstract

Inulinases are classified among hydrolases, target the β-(2,1)-linkage of inulin and can be used to produce high-fructose corn syrup, fructo-oligosaccharides and alcohol, conferring upon inulinases significant potential for application in the food industry. A total of 28 strains that are capable of producing inulinase were isolated from the rhizosphere soil of Jerusalem artichoke (Helianthus tuberosus L.). Of these strains, the bacterial strain ni-3 was isolated through further screening. Based on its morphological, physiological and biochemical characteristics, ni-3 was identified by 16S rDNA sequences and systematic analysis. The 16S rDNA sequences of this strain had 99.5% similarity with the partial sequence of Brevibacillus centrosporus, denominated as B. centrosporus ZF-9. The optimum conditions of fermentation were investigated. The optimum conditions for inulinase were as follows: inulin 45 g/L, yeast extract 11 g/L, and Na2HPO4 20 g/L. Under these conditions, the inulinase activity of B. centrosporus ZF-9 reached 6.41 U/mL.