Abstract: This work is to breed a strain of Klebsiella pneumonia with high xylose tolerance,to analyze its transcriptomics,and to optimize the fermentation conditions of producing 2,3-butanediol（2,3-BD）. Firstly,the adaptive evolution method was used to screen a K. pneumonia strain KP2 with high xylose tolerance and high yield of 2,3-BD. Then,the transcriptome analysis and the optimization of fermentation conditions were conducted. Results showed that the xylose conversion rate and 2,3-BD production by KP2 increased by 174.5% and 227%,respectively. The transcriptome analysis of parental strain KPG and KP2 demonstrated that 242 genes were up-regulated and 263 genes were down-regulated in KP2. The pathway analysis further revealed that the changes of transcripts mainly occurred in signal transduction,carbohydrate metabolism,energy metabolism and other material metabolism. Under the initial concentration of xylose 120 g/L in 1 L reactor,the optimal fermentation conditions were as follows：35℃,230 r/min,0.7 L/min（aeration）,and pH 5.9. Under this optimal conditions,the maximal production of 2,3-BD reached 43.9 g/L,which was improved by 33.3% compared to that before optimization. In sum,we successfully obtained the strain of producing 2,3-BD by efficiently using xylose,the mechanism of phenotypic change was expounded at the molecular level,and the optimal fermentation conditions were determined. The result may provide reference for the production of 2,3-BD,and has a certain guiding significance for the biological production of 2,3-BD.

Key words: adaptive evolution, Klebsiella pneumonia, transcriptomics analysis, response surface methodology, 2, 3-butanediol