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영어

The 2,3-butanediol (2,3-BD) is a platform chemical for many synthetic polymers and resins (Zeng and Sabra 2011). A newly isolated Raoultella sp. B6 from an oil-contaminated soil sample produced 2,3-BD from various single carbon sources such as glucose, galactose, xylose, sucrose, etc. To optimize fermentation conditions for 2,3-BD production, we tested different aeration conditions by controlling agitation speed and air flow. The pH of culture was controlled at 5.5 after the initial pH 7.0 decreased to 5.5 during the cell growth. With 200 rpm of the agitation speed and 0.5 vvm of air flow, 2,3-BD production was 64.7 g/L with the productivity of 0.54 g/L/hr, but formate, a by-product, was also produced up to 24.6 g/L. To further increase 2,3-BD production with less by-product formation, we increased agitation speed (400 rpm) and air flow (1 vvm). Consequently, 2,3-BD production increased up to 102.6 g/L with the productivity of 2.12 g/L/h, implying that aeration was a key factor for high production of 2,3-BD. Further improvement of 2,3-BD production was investigated by overexpressing 2,3-BD synthesis-related genes such as acetoractate synthase (budB), acetolactate decarboxylase (budA), and 2,3-butanediol dehydrogenase (budC). In the flask test, the budABC overexpression strain showed the highest growth level and low by-products compared with the wild type strain, suggesting possible further enhancement of 2,3-BD using the budABC overexpression strain under the optimized fermentation conditions.