3-Hydroxy Propyl Aldehyde Influence Klebiella Metabolism And The Construction Of Genetic Engineering Bacteria

1,3-propanediol(PDO) is an important chemical raw material. The most important application of PDO is producing the new type of polyester poly propylene terephthalate (PTT). In recent years,1,3-propanediol production with the byproduct of biodiesel production has become an important way to increase the economy of biodiesel industry.The effect of3-hydroxypropionaldehyde(3-HPA) on the metabolism of Klebsiella pneumoniae was studied firstly. The cell growth and PDO production of K. pneumoniae HR521stopped with the initial glucose concentration was70g/L. The high concentration of3-HPA accumulation was detected in the broth. Semicarbazide hydrochloride can induce the synthesis of3-HPA. The effect of semicarbazide hydrochloride on the cell growth and PDO production of K. pneumoniae HR521was discussed. Low concentration of semicarbazide hydrochloride can induce the3-HPA production in a little amount and enhance the cell growth of K. pneumoniae HR521. However,3-HPA can accumulate with high concentration in the broth when semicarbazide hydrochloride concentration was above lOg/L. And the fermentation stopped under such condition.The effect of3-HPA on the key enzyme and co-enzyme were studied. Compared to the condition of low3-HPA accumulation (2.45mmol/L), the activity of GDHt increased one fold and the activity of GDH and PDOR decreased33.33%and37.5%, respectively under high concentration of3-HPA accmulation. So, the3-HPA synthesis rate increased and PDO transformation rate decreased, which led to the3-HPA accumulation. On the other hand, under high concentration of3-HPA accumulation, NADH2content decreased to38.49%and NAD+increased to43.36%of that under low3-HPA accumulation condition. So, the absence of NADH2is another reason of fermentation cease of K. pneumoniae.Based on the above results, the polyhydroxybutyrate pathway was induced into the K. pneumoniae in order to improve the tolerance of K. pneumoniae to3-hydroxypropionaldehyde. PHB was detected in the engineered K. pneumoniae after IPTG induction. The optimized IPTG concentration was0.5mmol/L. With the initial glucose was70g/L, the wild type strain Klebsiella pneumoniae stopped growing due to high accumulation of3-HPA, while the engineered strain K.P/pCAB could produce PDO normally. The PDO concentration reached31.3g/L, which increased39.71% than that of wild type strain and the PDO yield was43.9%. So, the engineered Klebsiella pneumoniae had higher resistance to3-HPA accumulation than that of the wild type strain.This work is helpful for the deep understanding of1,3-propanediol metabolic mechanism of K. pneumoniae, and also provides a new way for the further strain optimization of K. pneumoniae.