Effects Of Lactic Acid And 3-hydroxy-propionaldehyde On 1,3-propanediol Production By Klebsiella Pneumoniae

This thesis mainly studied the effects of lactic acid and 3-hydroxy-propionaldehyde on 1,3-propanediol fed-batch fermentation by Klebsiella pneumoniaeFirst of all, through adding promote mutagen LiCl、changing the concentration of mutagenic bacteria and the mutagenic time, the original mutagenesis methods of our laboratory was improved, the mutation rate, screening efficiency were increased and a new strain with high yield of 1,3-propanediol was screened out.Through the analysis of metabolites of the new species, It was found that the main difference between the new strain and the original strain’metabolites was the concentration of lactate, which inspired the exploration of the new fermentation process of the new strain.In the exploration of the new strain’s fermentation conditions, It was found that under different conditions, some of the features of the new strain were the same with the original strain, but the new strain was more sensitive to the initial glycerol concentration; and there was a close relationship between lactate concentration and the final fermentation results:the higher the final concentration of lactate,the lower the 1,3-PD concentration was.Reported in the literature that lactate will inhibit the bacteria activity of Klebsiella pneumoniae, thus affecting the yield of 1,3-propanediol. It was well known to all that 3—ydroxypropionaldehyde also could inhibit the activity of Klebsiella pneumoniae, then reduced the yield of 1,3-propanediol, which inspired the research into the relationship of lactate and 3-HPA’effect on the 1,3-PD production by Klebsiella Pneumoniae.With the help of the genetic engineering strain constructed by my colleges of molecular group, series of experiments was designed to examine the relationship of lactate and 3-HPA’effect on the 1,3-PD production fermentation, and a conclusion was found that lactic acid is not the main factors affecting the fermentation results.