Book of Abstracts :: 14th International Symposium on Biopolymers (ISBP2014)
Abstract: 11-1


Oral (Tema Livre)
11-1Production of Poly(3-hydroxypropionate) from Glucose by Recombinant Escherichia coli
Authors:Dechuan Meng (THU - School of Life Sciences Tsinghua University) ; Guoqiang Chen (THU - School of Life Sciences Tsinghua University)

Abstract

Poly(3-hydroxypropionate) (P3HP) is the strongest polyhydroxyalkanoates (PHA) made by bacteria so far, its Young’s modulus could reach to 3 GPa. Bacterial synthesis of homopolymer P3HP was first reported using glycerol as carbon source in two-step fed-batch fermentations in 2010. While P3HP production are still facing the problem of high costs, it has become possible to engineer bacteria for the synthesis of PHA with the desirable structures by creating novel polyhydroxyalkanoate (PHA) synthesis pathways using synthetic biology approach. In this study, recombinant Escherichia coli harboring a synthetic pathway consisting of 9 heterologous genes was constructed to produce P3HP using glucose as the main carbon source. The genes for glycerol-3-P dehydrogenase and glycerol-3-P phosphatase (gpd1 and gpp2 from Saccharomyces cerevisiae) which could catalyze glucose into glycerol firstly, the genes for glycerol dehydratase and its reactivating factor (dhaB123 and gdrAB from Klebsiella pneumoniae) which could transfer glycerol to 3-hydroxypropionaldehyde, the gene for propionaldehyde dehydrogenase (pdup from Salmonella typhimurium) which could transfer 3-hydroxypropionaldehyde to 3-hydroxypropionyl-CoA, and the gene for polyhydroxyalkanoate synthase (phaC from Ralstonia eutropha) which could polymerize 3-hydroxypropionyl-CoA into poly(3-hydroxypropionate) were cloned and assembled in the host strain. The recombinant E. coli produced 5 g/L cell dry weight containing 20% P3HP using glucose as the main carbon source in a 48 h shake flask growth in LB medium. P3HP was structurally confirmed by gas chromatography as well as 1H and 13C NMR studies. At the same time, when phaA and phaB from Ralstonia eutropha were introduced into the above recombinant E. coli, it produced the copolymer P3HB3HP using glucose as the main carbon source. Further investigation should be directed to produce P3HP in the fermentor under optimized culture conditions. In this work, metabolic engineering approaches were successfully employed to produce P3HP homopolymers and P3HB3HP copolymers. The new pathway to produce P3HP was the highest P3HP yield using glucose as the main carbon source reported so far, which will make the strong P3HP more attractive in terms of low production cost.


Keywords:  PHA, Poly(3-hyroxypropionate), Synthetic biology, Escherichia coli