The Effect Of Enhencement Of The Reductive Pathway On 1,3-propanediol Production In Klebsiella Pneumoniae

It has been studied many years that the effect of the key enzymes,which was in the reductive pathway of glycerol metabolism especially,in Klebsiella pneumoniaeon the 1,3-propanediol production or conversion rate.However,most of the previous studies were about 1,3-propanediol oxidoreductase while the glycerol dehydratase or the others were studied much litter.Now the effect of glycerol dehydratase(dhaB)and aldehyde dehydrogenase(puuC)on 1,3-propanediol production was proposed in our stduy.In this study,we builded the expression vectors of dhaB-pETac and puuC-pETac and introduced them in KG2(lactate-dificeint strain)and KG3(lactate-and 2,3-butandiol-dificeint strain)to construct four mutants of KG2-dhaB,KG3-dhaB,KG2-puuC and KG3-puuC,respectively.The cell growth,1,3-propanediol production,by-products production and metabolic flux were determined through the fed-batch fermentation process.Furthermore,the KG-puuC mutants were studied by overexpression or moderate expression of puuC via addition or not addition of IPTG.The results showed that expression of dhaB decresed cell growth and 1,3-propanediol production.As for the gene puuC,an improvement in 1,3-propanediol production was only achieved in a lactate-deficient strain via moderate expression of puuC;the cell growth and 1,3-propanediol productivity increased by 3.4%and 15%compared with the control,respectively,while,in the strain of KG3-puuC,cell growth and 1,3-propanediol productivity decreased by 4%and 15%compared with mutant KG3,respectively.These results indicate that moderate expression of puuC could be beneficial for cell metabolism,which can be accomplished by enhancing 1,3-propanediol productivity in a lactate-deficient strain via moderate expression of puuC.