초록
2,3-Butanediol (2,3-BDO) is a value-added chemical with great potential for the industrial production of synthetic rubber, plastic and solvent. For microbial production of 2,3-BDO, in this study, Klebsiella oxytoca NBRF4 was constructed by chemical mutation and screening against NaBr, NaBrO<SUB>3</SUB> and fluoroacetate. Among metabolic enzymes involved in the production of lactate, acetate and 2,3-BDO, K. oxytoca NBRF4 possessed 1.2 times lower specific activities of lactate dehydrogenase and phosphotransacetylase, and 22% higher specific acetoin reductase activity than the K. oxytoca ATCC43863 control strain. A series of batch fermentations in a defined medium and application of a statistical tool of response surface method led to the determination of optimal culture conditions: 10% dissolved oxygen level, pH 4.3 and 38<SUP>o</SUP>C. The actual results of batch fermentation at the optimal conditions using 44g/L glucose were coincident with the predetermined values: 14.4g/L 2,3-BDO concentration, 0.32g/g yield. To increase 2,3-BDO titer, fed-batch fermentation of K. oxytoca NBRF4 was performed by an intermittent feeding of 800g/L glucose to control its concentration around 5-20g/L in the culture broth. Finally, 34.2g/L 2,3-BDO concentration and 0.35g/g yield were obtained without organic acid production in 70hours of the fed-batch culture, which were 2.4 and 1.2 times higher than those of the batch fermentation using 44g/L glucose.