Screening of HA-producing lactic acid bacteria and culture condition optimization of selected bacterium by Taguchi method

Hyaluronic acid (HA) is a major component of the extracellular epithelial, neural and connective tissue of vertebrates, as well as of extracellular microorganisms. This polysaccharide has specific applications in ophthalmology, orthopedic, cosmetics and tissue engineering due to features such as high viscosity and biocompatibility. Animal tissues and streptococci have a major role in producing hyaluronic acid, but because of problems such as protein contamination and the presence of endotoxin, attention has been drawn to the GRAS bacteria for producing hyaluronic acid. Lactobacilli are probiotic bacteria that have diverse uses. The production of biochemical macromolecules by this group of bacteria is a priority because they are GRAS. Hyaluronic acid production for the first time in these GRAS bacteria including Lactobacillus acidophilus PTCC1643, Lactobacillus rhamnosus PTCC1637, Lactobacillus casei PTCC1608 and Streptococcus thermophilus PTCC1738 were investigated. In the first step, Hyaluronic acid was isolated from specific culture medium and partially purified by ethanol precipitation daily for 96 hours. Carbazole method was used to measure the production of hyaluronic acid. Based on results, Lactobacillus rhamnosus produced about 0.4 g/l of hyaluronic acid at 96 hours. The increase of HA was also investigated using optimization culture medium by Taguchi design. By using this method, the optimum points of the factors were determined and the hyaluronic acid production increased by 162%.