Bear bile, one of the most famous animal drugs in Traditional Chinese Medicine (TCM), has been recorded in ancient Chinese medicine book as a significant method to treat hepatic and biliary disorders. Aside from bear bile's efficacy in TCM, its marked pharmacological effects on fever fighting, detoxification and pain reduction have been confirmed through modern investigations. However, the increasing demand from bear bile has caused bears to be in an endangered state: bear poaching and illegal animal trade have greatly dwindled the number of the wild Asiatic black bear. Apart from that, bear bile farming industry has established in Asia to extract bile through “milking” from the bears, which is basically operated through surgically implanting a permanent catheter in the animal's gall bladder then obtain the drips. It is unquestionable that the bear bile farming process will lead to both physically and psychologically damage in bears.

To find substitutes or alternative of bear bile farming, our team will be working on biological synthesis of the main effective component of this important medicine, UDCA. And this biological method will be more efficient and also cheaper than the original chemical approach, which is used in the current chemical UDCA synthesis industry.

We found that it is possible to convert the main component of goose bile, CDCA, into UDCA, by using two enzymes to catalyst the reaction. The reaction will proceed in two steps. First, CDCA is oxidized in the presence of 7α-HSDH, coupled by the regeneration of NAD+ with the enzyme LDH, and pyruvate. Similarly, in the second reduction step, the enzyme 7β-HSDH catalyze the reaction of 7-oxo-LCA to UDCA with glucose dehydrogenase (GDH) and glucose for the regeneration of cofactor (NADPH) .

Our mission is to express the four enzymes (7α-HSDH, 7β-HSDH, GDH, and LDH) in the E.coli and test their activities. After expression, all the enzymes will be able to bind to a chitin column because a fragment encoding a chitin binding domain is fused with the target genes. This specific design excels in two specific ways: first, by controlling the presence of the chitin column in the solution, we can control the process of the reaction. Second, this design simplified the effect of the specific target protein in the extraction of purified bacteria. At last a machine including the reaction efficiency measuring system and the enzyme addition controlling system will be made.