Inhibitory mechanism of 3-hydroxypropionaldehyde accumulation in 1,3-propanediol synthesis with Klebsiella pneumoniae

3-Hydroxypropionaldehyde accumulation may cause the cessation of 1,3-propanediol sustained production with glycerol by Klebsiella pneumoniae . The impeller tip speed shift from higher to lower speed at glycerol excess or the pulsed glycerol feeding could lead to an abrupt increase of the 3hydroxypropionaldehyde concentration (up to 10 mmol/l) in 10 min. The intracellular consequence of the 3-hydroxypropionaldehyde accumulation has not yet been elucidated. The rapid accumulation of 3hydroxypropionaldehyde relying on the impeller tip speed shift was employed to investigate the influences of 3-hydroxypropionaldehyde to the activities of nine key enzymes related to glycerol metabolism, CO 2 and O 2 levels in off-gas, cell growth and 1,3-propanediol synthesis. Compared with that at 1.19 mmol/l 3-hydroxypropionaldehyde in broth, the residual enzymatic activities of the nine key enzymes ranged from 9.44 to 74.68% in the cultures at 7.5 mmol/l 3-hydroxypropionaldehyde in broth. The inhibitions of cell growth and the 1,3-propanediol synthesis were unnoticeable at the low level of 3hydroxypropionaldehyde. By contrast, the CO 2 and O 2 levels changes in off-gas response to the 3hydroxypropionaldehyde accumulation were less than 15 min. These results suggest that 3hydroxypropionaldehyde inhibited the growth and metabolism of K. pneumoniae in a more complicated manner.