The use of undegradable petroleum-based plastics has caused serious environmental pollution. To resolve this problem fundamentally, an efficient way is to develop the biosynthesis of degradable plastics, which has been listed as key areas of high-tech industrialization by national policy. Poly(3-hydroxypropionate) (P3HP) is a new type of biodegradable plastic with good material properties and broad range of applications. Unfortunately, all known organisms cannot produce P3HP naturally.

The Biobased Chemicals Group at Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, has made a series of progress on the biosynthesis of P3HP. A large numbers of genes probably involved in the P3HP synthesis from various organisms were cloned and expressed in E. coli strains, and the corresponding proteins were purified and characterized in vitro. Based on the results of enzyme activity tests, appropriate genes were selected and assembled into two novel P3HP biosynthetic pathways. The engineered E. coli strain harboring either pathway can produce P3HP using renewable inexpensive carbon sources, such as glucose and glycerol. Under optimized growth conditions, the engineered strain accumulated 10.1 g/L P3HP in fed-batch fermentation, which represented the highest production so far.

Figure 1. P3HP and its biosynthetic pathways (Image by Biobased Chemicals Group)

To further improve the material properties, a second monomer, 3-hydroxybutarate (3HB), was incorporated into P3HP polymer. Two parallel synthetic pathways controlled by independent regulatory systems were used to produce the 3HP and 3HB monomers, respectively. Through tuning the expression level of appropriate genes, copolymers were synthesized with a wide range of 3HP fraction. The mechanic and thermal properties of copolymers was significantly improved.

This research is financially supported by Chinese Academy of Sciences, Ministry of Science and Technology, and National Natural Science Foundation of China. Until now, relevant results have been published in journals like Bioresour Technol and J Microbiol, and two invention patents were applied. The key technology packages for P3HP biosynthesis were established, that provides a theoretical basis for the industrial fermentation production of P3HP.

Related papers:

1.      Biosynthesis of poly(3-hydroxypropionate) from glycerol by recombinant Escherichia coli. Bioresour Technol, 2013, 131:548

http://www.sciencedirect.com/science/article/pii/S0960852413001193

2.      Biosynthesis of Poly(3-hydroxypropionate-co-3-hydroxybutyrate) with fully controllable structures from glycerol. Bioresour Technol, 2013, 142:741

http://www.sciencedirect.com/science/article/pii/S0960852413009115

3.      Biosynthetic pathway for poly(3-hydroxypropionate) in recombinant Escherichia coli. J Microbiol, 2012, 50(4): 693

http://link.springer.com/article/10.1007/s12275-012-2234-y

Contact:

Prof. XIAN Mo