15-13: Selective production of 2,3-BDO and acetoin using a newly isolated Klebsiella oxytoca M1

A 2,3-butanediol (2,3-BDO)-producing bacterium, the strain M1, was isolated from a tidal flat soil sample. It was identified to be Klebsiella oxytoca based on its 16S rDNA sequence and physiological analysis. Interestingly, K. oxytoca M1 produced 15.5 g/L of 2,3-BDO at 30°C after 24 h from glucose, while 15 g/L of acetoin was produced at 37°C after 48 h. To investigate factors influencing product profiles according to temperature, the activity of acetoin reductase (AR) catalyzing the conversion of acetoin to 2,3-BDO was analyzed with crude protein from K.oxytoca M1. The acetoin reductase activity of K.oxytoca M1 cultivated at 37°C was rapidly decreased after 12 h of cultivation. Especially, the acetoin reductase activity of K.oxytoca M1 cultivated at 30°C was up to 10-fold higher than that of 37°C at 12 h. The mRNA level of the budC encoding acetoin reductase at 30°C was stable until 12 h and decreased slightly after 12 h cultivation. In contrast, the budC transcript at 37°C was reduced considerably after 12 h cultivation compared with that at 30°C. Taken together, the results strongly indicated that acetoin accumulation at 37°C was due to the low activity of acetoin reductase at 37°C. Based on the results, it is concluded that K. oxytoca M1 can produce either 2,3-BDO or acetoin selectively by controlling cultivation temperature.