Glycerol can be utitlized in various ways of biological transformation to industrially valuable products such as 3-hydroxy-propionaldehyde (3-HPA), dihydroxycetone (DHA), and 1,3-propanediol (PDO).
The market for 1,3-propanediol is currently over 100 million pounds per year and is growing rapidly. Commercial synthesis of 1,3-propanediol starts from acrolein in Degussa’s process and from ethylene oxide in Shell’s process.
Recently a new recombinant technology was worked out with the leadership of DuPont and Genencor in which a recombinant Escherichia coli converts glucose directly to 1,3-PD.
Although this biological way of PDO production is much more environmental friendly an enzymatic process would be even more advantageous.
For years our research group have been working on a new enzymatic process in order to produce PDO and DHA simultaneously from glycerol in a coenzyme-regenerating system.
For this biotransformation three key enzymes are needed: Glycerol-dehydratase (GDHt; E.C.4.2.1.30) (the applied Clostridium butyricum origin enzyme is B12-independent), 1,3-propanediol-oxydoreductase (PDOR; E.C.1.1.1.202) and glycerol-dehydrogenase (GDH, E.C. 1.1.1.6) which produces DHA. All these enzymes may be produced by microbial fermentation.
The aim of our work was to develop immobilized enzymes suitable for glycerol to propanediol bioconversion and develop a method to measure the immobilized enzymes activity. We tried a covalent method applying chitosan matrix activated with glutaraldehyde. It was detected that PDOR and GDH enzyme bind to chitosan beads and their enzymes activity was higher than that of the soluble enzymes. The immobilization of the third enzyme (GDHt) is now under investigation.