Background

Biorefineries for chemicals have attracted a great deal of interest because they can alleviate the dependence on oil supply for the production of platform chemicals, reduce environmental pollution, and ensure sustainable develop-ment [1,2]. Biological production of 2,3-butanediol (2,3-BD) has increased remarkably because of its wide industrial applications [3-5]. Many microorganisms classified in the genera Enterobacter, Klebsiella, Serratia, and Bacillus can produce 2,3-BD [3,4]. K. pneumoniae is a potentially useful producer in the industry because of its wide substrate spectrum, high efficiency, and cultural adaptability [6-8]. The fermentation pathways of mixed acid-2,3-BD in bacteria have been intensively studied [4]. Numerous studies have investigated the use of metabolic engineer-ing to modify the metabolic pathways for improving 2,3-BD production in Enterobacter aerogenes [9], Bacillu