APPLICATIONS OF TECHNOLOGY:
- Isoprenoid-based biofuels
- Flavors and fragrances
- Rubber (isoprene)
- Improves isoprenoid production rates
- Conserves metabolic materials (carbon) and energy
- Significantly higher pathway theoretical yield compared to wild type DXP pathway (particularly using feedstocks containing xylose)
Researchers at the Joint BioEnergy Institute (JBEI) have generated a new synthetic pathway in cells to 1-deoxyxylulose-5-phosphate (DXP) using a metabolic route dependent on mutations identified in the ribB gene. A second route was also discovered, which involves the E. coli genes yajO and xylB. Of the two mechanisms, the ribB route is more efficient, and has been shown to complement an E. coli dxs (DXP synthase) knockout to wild type growth levels. Both routes allow more direct conversion of carbon to terpenoid compounds circumventing the typical, but inherently inefficient, route to DXP. Terpenoids are key ingredients in flavors and fragrances. They also offer a pathway to naturally derived isoprenoid-based biofuels and materials, such as rubber, as well as pharmaceuticals and neutraceuticals.
The JBEI process results in the conservation of 17% of carbon being converted to terpenoid products. Conserving metabolic materials (carbon) and energy is crucial to producing biofuels and other valuable products priced competitively with petroleum-derived products.
The novel pathways to DXP entail conversion of xylulose-5-phosphate to DXP, which circumvents the loss of CO2 and provides a higher theoretical yield, particularly if xylose is included as a carbon source. It also provides a second metabolite pool (the essential pentose phosphate pathway) for isoprenoid biosynthesis. In the case of having a mixed carbon source (for example, xylose and glucose from a hemicellulose feedstock), it is envisioned that a large fraction of the xylose component could be primarily converted to the isoprenoid product since the carbon is diverted at the entry point into metabolism (xylulose-5-P). The novel routes into the DXP pathway could also be used in conjunction with the normal DXP-mediated route to maximize flux.
Prior to this invention, DXP was produced by the condensation of pyruvate and glyceraldehyle-3-phosphate (G3P), an inefficient method because it involves assimilation of the sugar into central metabolic pathways. This normal route for generation of DXP from pyruvate and G3P also results in the loss of CO2 during the reaction, effectively losing one sixth of the feedstock carbon. In addition, pyruvate and G3P are required for many metabolic pathways in the cell with only a small portion of these precursors directed to DXP biosynthesis.
DEVELOPMENT STAGE: The researchers have demonstrated efficient complementation of dxs knockout in E. coli through expression of ribB mutants, either on a plasmid, or via mutation of the chromosomal copy of ribB. They have also demonstrated significantly increased terpene (amorphadiene) production using ribB mutants in a strain of E. coli containing no other modifications to the DXP pathway. It is anticipated that the benefit of these novel routes will be most apparent when combined with a strain of E. coli that harbors an engineered DXP pathway, and the JBEI scientists are currently working on this demonstration.
STATUS: Published US Patent Application US20130052692 available at uspto.gov. Available for licensing or collaborative research.
SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:
REFERENCE NUMBER: EJIB-3006
The Joint BioEnergy Institute (JBEI, www.jbei.org) is a scientific partnership led by the Lawrence Berkeley National Laboratory and including the Sandia National Laboratories, the University of California campuses of Berkeley and Davis, the Carnegie Institution for Science and the Lawrence Livermore National Laboratory. JBEI’s primary scientific mission is to advance the development of the next generation of biofuels.