From the 1,4-butanediol wikipedia entry:

Genomatica (a San Diego-based company) has genetically engineered E. coli to metabolize sugar into 1,4-butanediol. They expect to build and begin operating a pilot plant by the end of 2009. Genomatica CEO Christopher Gann said the process consumes 32,000 BTU per pound of 1,4-butanediol (75 MJ/kg), far less than the acetylene-based process, and does not have any by-products.[6][7] Commercial Scale Production was announced in 2013 by Genomatica and DuPont Tate & Lyle Bio Products Co. with a successful compaign that produced 2000 metric tons of BDO by direct fermentation.[8]

more info:
http://biopol.free.fr/index.php/building-blocks-for-bioplastics-pure-butanediol-from-natural-sugars/
(Wish I could get my hands on a sample of that strain...)

Biodegradable plastics (bioplastics) are on the rise in these days of ecological awareness, and 1.4-butanediol seems to be a common building block for the production of biodegradable polybutylene esters, especially now that this company achieved a cost-effective process for the biosynthesis of 1.4-butanediol from sugar in >99% purity. Common bioplastics are polybutylene terephthalate (PBT),  Polybutylene succinate (PBS),  polybutylene adipate (PBA) and last but not least: poly-4-hydroxybutyrate (P4HB).

Regarding the latter this article is of some interest:

Medical applications of poly-4-hydroxybutyrate: a strong flexible absorbable biomaterial
David P. Martin, Simon F. Williams
Biochemical Engineering Journal, Volume 16, Issue 2, November 2003, Pages 97–105
http://www.sciencedirect.com/science/article/pii/S1369703X03000408

Abstract
Poly-4-hydroxybutyrate (P4HB) is being developed as a new absorbable material for implantable medical applications. P4HB promises to open up new opportunities for the development of medical applications by offering a new set of properties that are not currently available. The absorbable biomaterial is strong yet flexible, and degrades in vivo at least in part by a surface erosion process. While the chemical structure of P4HB is similar to that of current absorbable polyesters used in implantable medical products, P4HB is produced by a fermentation process rather than through a chemical synthesis. P4HB is a thermoplastic material that can be processed using standard plastics processing techniques, such as solution casting or melt extrusion. The strength of P4HB fibers prepared by melt extrusion compare well with that of traditional suturing materials, however, P4HB is typically more flexible. P4HB should find use in a wide variety of medical fields such as cardiovascular, wound healing, orthopedic, drug delivery, and tissue engineering applications. This paper describes some of the basic properties of P4HB and several of its potential applications in medicine.

If in the future we will see more of these materials, it would be a good idea to think about how we can depolymerize these polymers for the production of 1,4-butanediol from polybutylene esters of GBL from P4HB.

PBT already seems pretty available commercially, I've seen some designer chairs that apparently were PBT. How easily would this be depolymerised by heating, as in the well-known case of polystyrene? The butanediol ester monomer should be easily saponified and the 1,4-butanediol distilled, I think.... I hope.

Anybody have some ideas or information to share on this?