Effect On 1,3-propanediol Production Of K.pneumoniae By Addition Of Cofactors

According to the characteristics of multi-enzyme catalysis of 1,3-propanediol (1,3-PD) production by K. pneumoniae, cofactors which may change the energy or reducing equivalent(NADH) level of the cell, including glucose as cosubstrate,ATP,reducing agent and oxygen, were introduced into fermentation process. Effects of cofactors on 1,3-PD production of K.pneumoniae were investigated. The conclusions are summarized as follows: Firstly, effects of two substrates(glucose/glycerol) on 1,3-PD production of K.pneumoniae were studied. It showed that when glucose was added as cosubstrate in anaerobic fermentation, it was consumed faster than glycerol and could promote cell growth. Glucose of low concentration increased 1,3-PD final concentration slightly, but decreased the yield of glycerol to 1,3-PD; Glucose of high concentration increased the yield of glycerol to 1,3-PD,but decreased 1,3-PD final concentration. Glucose had an inhibitory effect on glycerol dehydrogenase and 1,3-PD oxidoreductase。Secondly, effects on 1,3-PD production of K.pneumoniae by addition of ATP were studied. It showed that addition of ATP had an inhibitory effect on cell growth and did not increase 1,3-PD final concentration obviously, but increased 1,3-PD production per cell considerably. Addition of ATP can increase the yield of glycerol to 1,3-PD .Additionally, the effect of ATP on glycerol dehydratase reactivation of resting cell was investigated. It showed that after ATP drove reactivation, the catalysis efficiency of inactivated glycerol dehydratase did not decrease obviously, and the enzyme was recovered after many cycles of "inactivation/reactivation".Thirdly, effects of the redox potential manipulation on 1,3-PD production of K.pneumoniae were studied. Addition of reducing agent and intermittent supply of oxygen was used respectively in order to change the redox potential of fermentation system. Adding VC can promote 1,3-PD synthesis, but could not increase the yield of glycerol to 1,3-PD. Addition of VC considerably decreased the concentration of 3-hydroxypropionaldehyde inside and out of cell and increased the activity of glycerol dehydrogenase and 1,3-PD oxidoreductase. Intermittent supply of oxygen decreased the ratio of NADH/NAD, but increased the activity of glycerol dehydrogenase at the early stage of fermentation.