Hyaluronic acid production in Streptococcus equi species

Hyaluronic acid (HA) is a glycosaminoglycan which exists ubiquitously in all organisms where it possesses a range of important functions. Due to the rheological properties and biocompatibility of HA solutions, it has been employed in a variety of medical applications. The rheology of a HA solution is a consequence of the concentration and molecular weight of the HA present. The current commonly used method for HA production is bacterial fermentation using Group C Streptococcus species which produce HA as a protective capsule in order to evade immune responses of their hosts. These are fastidious organisms and the fermentation process requires strict regulation of culture parameters in order to obtain optimum yields. A disadvantage of bacterial HA production is that the molecular weight of the product is often lower than the ideal range and the optimal yield is low at 5-10 g/L. The aim of this project is to investigate metabolic and genetic factors influencing HA capsule production in subspecies of the Group C Streptococcus equi. The study identifies a novel strain of S. equi capable of producing high concentrations of HA under the conditions studied and evaluates a currently used industrial procedure. Genomic and proteomic differences between subspecies of S. equi and mucoid/non-mucoid phenotypes have been investigated. The effects of the antibiotic phosphomycin on growth and HA production have also been explored. Collectively the results of this study have opened the scope of HA production research beyond the conventional methods used to date.