Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
3-Hydroxypropionic acid (3-HP) and 1,3-Propandiol (1,3-PDO) are value-added chemicals for bioplastic production. To produce 3-HP and 1,3-PDO simultaneously from glycerol, Escherichia coli was engineered to express Lactobacillus brevis glycerol dehydratase (DhaB), E. coli K12 aldehyde dehydrogenase (AldH) and Klebsiella pneumoniae propanediol oxidoreductase (DhaT). Three genes were cloned to be expressed under the control of the IPTG-inducible T7 promoter. In a batch fermentation using 60 g/L glycerol and 20 g/L glucose, co-expression of the dhaB, aldH and dhaT genes led to production of 16.4 g/L 3-HP and 6.18 g/L 1,3-PDO, which were 2.2 and 4.9-fold increases compared with those of the control strain expressing dhaB and aldH, respectively. Fed-batch fermentation of E. coli BL21star(DE3)/pELDRR+pCDaT was carried out in a bioreactor containing a defined medium with 20 g/L glucose. After the exhaustion of initial glucose, 60 g/L glycerol, 0.2 mM IPTG, 20 µM coenzyme B12 were added into the bioreactor and a feeding solution consisting of 400 g/L glucose and 28 g/L MgSO4 was fed at the pH-STAT mode of operation. Finally, 43.4 g/L 3-HP and 8.14 g/L 1,3-PDO were obtained in the fed-batch cultivation, which were 6.1 and 1.6-times higher than those for the same culture of the control strain, respectively. In addition, the yields of 3-HP and 1,3-PDO based on the amount of consumed glycerol were achieved at 0.70 mol/mol and 0.15 mol/mol, respectively. Consequently, co-expression of the dhaB, aldH and dhaT genes considerably enhanced the production of not only 1,3-PDO but also 3-HP.