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In batch mode, Klebsiella pneumoniae growth and 2,3-butanediol/acetoin formation are increasingly inhibited by initial sucrose concentrations (S0) over 60 g/L. At non inhibitory conditions, a maximum sucrose consumption rate of 1,5 g/L/h was measured. With S0=204 g/L however, this rate decreased to 0.15 g/L/h. K. pneumoniae fermented 204 g/L sucrose to produce 84.3 g/L of a mixture 2,3-butanediol/acetoin with a yield of 0.41 g/g and a productivity of 1.06 g/L/h. Higher oxygen transfer rates improved the overall process rate but the product yield was reduced. Avoiding substrate inhibition, by performing the fermentation in fed-batch mode, a final 2,3-butanediol/acetoin concentration of 80.0 g/L was achieved. In this case, a productivity of 2.63 g/L/h and a product yield of 0.37 g/g were calculated.