Co-production Of3-Hydroxypropionic Acid And1,3-Propandediol By An Engineered Klebsiella

3-Hydroxypropionic (3-HP) and1,3-propandediol (1,3-PDO) are important three carboncompounds of great commercial value.3-HP is a primary monomer of polyhydroxyalkanoate(PHA) and P-(3-HP).1,3-PDO is also a chief monomer of polytrimethylene-tereph-thalate(PTT). In the process of biosynthesis with glycerol as substrate, dehydrogenation andreduction (NADH/NAD+) is one of the main factors influencing the synthesis of twocompounds, and co-production can be effective in reducing carbon flow pathway to relatedby-products. In this research, the aldehyde dehydrogenase gene from Escherichia coli wasexpressed to construct recombinants Klebsiella. pneumoniae ZG27/pUC19-aldH and K.pneumoniae ZG40(budC)/pUC19-aldH. Besides, the co-production of3-HP and1,3-PDOand effect of budC knockout to co-production was analyzed.This study used genetic modification techniques, completed the construction ofengineered K. pneumoniae, K. pneumoniae ZG27/pUC19-aldH and K. pneumoniae ZG40(budC)/pUC19-aldH, and on this basis, the biosynthesis of3-HP and1,3-PDO of the tworecombinants was investigatied. The biomass of the aldehyde dehydrogenase expressionstrains K. pneumoniae ZG27/pUC19-aldH and K. pneumoniae ZG40(budC)/pUC19-aldHare higher than the corresponding starting strains K. pneumoniae ZG26/pUC19and K.pneumoniae ZG39(budC)/pUC19. And the total conversion rates of3-HP and1,3-PDO ofthe two recombinants are increased by11%and26%than the starting strains, respectively.According to the research of synthesis characters of3-HP and1,3-PDO in the twoengineered strains, K. pneumoniae ZG27/pUC19-aldH and K. pneumoniae ZG40(budC)/pUC19-aldH, we found pH had a great adjustment to the proportion of3-HP and1,3-PDO. Under the condition of pH6, the concentrations of3-HP and1,3-PDO were about11g·L-1、12g·L-1； under the condition of pH7, the concentrations of3-HP and1,3-PDOwere about16g·L-1、9g·L-1; under the condition of pH8, the concentrations of3-HP and1,3-PDO were about10g·L-1、14g·L-1. In addition, under the condition of pH7, after24hmicroaerobic fermentation, the accumulated1,3-PDO gradually converted to3-HP; budCknock-out stimulated an anaplerotic pathway of2,3-BD, caused an imbalance ofNADH/NAD+which further promoted the convertion of1,3-PDO to3-HP; under different pHconditions, the by-products such as succinic acid of two recombinants are lower than thecontrols.Based on the relative results of pH adjustment strategy, fed-batch culture of budC K. p/pUC19-aldH was carried out in a5L bioreactor under the condition of pH7.3-HP and1,3-PDO accumulated at the same time, and the final concentrations of3-HP and1,3-PDOwere40.2g·L-1and38.9g·L-1, respectively. This percentage of3-HP achieved in this studywas one of the highest in research of co-production reported thus far, and provided the basisof the industrialization for3-HP and1,3-PDO co-production.