Bioconversion of inulin to 2,3-butanediol by a newly isolated Klebsiella pneumoniae producing inulinase.

• Novel inulinase producer of K. pneumoniae for 2,3-butanediol production was isolated. • The enzyme was an intracellular inulinase with an optimal temperature of 30 °C. • Concentration of 2,3-butanediol and acetoin reached 80.4 g/L in batch fermentation. • A productivity of 2.23 g/(L⋅h) and yield of 0.426 g/g sugar were obtained. Inulin could be converted to bio-based chemicals by an inulinase producer without external inulinase, and the production of 2,3-butanediol was less than 50 g/L. In this work, a novel inulinase producer of Klebsiella pneumoniae H3 was isolated, and inulinase catalytic properties as well as 2,3-butanediol fermentation were investigated. The enzyme was an intracellular inulinase with an optimal pH of 6 ∼ 7 and a temperature of 30 °C. The use of inulin by H3 was dependent on the degree of polymerization (DP), and the average DP of inulin in fermentation broth increased from 2.82 to 8.08 in 24-h culture of batch fermentation. Acidic pretreatment was developed to increase inulin utilization by adjusting medium pH to 3.0 prior to sterilization. In batch fermentation with optimized medium and fermentation conditions, the concentration of target product (2,3-butanediol and acetoin) was 80.4 g/L with a productivity of 2.23 g/(L⋅h), and a yield of 0.426 g/g inulin. [ABSTRACT FROM AUTHOR]