Hyaluronic acid--a versatile biopolymer.

Since its discovery from bovine synovial fluid, hyaluronic acid has found application in several diverse areas. It is now extensively used in ophthalmic surgery, in the treatment of lameness in racehorses and as an ingredient in cosmetics. It can also be used in drug delivery, orthopedics, cardiovascular aids and in wound healing. Even so, its potential as a therapeutic agent is yet to be fulfilled. New improved products, formed by crosslinking hyaluronic acid with itself or other chemicals, are being produced. Hyaluronic acid is clearly a most valuable therapeutic biopolymer. This article reviews the properties of hyaluronic acid, its biosynthetic pathway and its methods of commercial production, and provides an estimation of its current and future world demand. Experiments designed to improve production economics have been performed in our laboratory. These involved control of glucose and yeast extract concentrations and fermentation pH. Hyaluronic acid production by Streptococcus zooepidemicus was found to be lower at pH 6.5 than at pH 7.1. A new method of extending the production of hyaluronic acid by S. zooepidemicus into the stationary phase has also been achieved.