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Hyaluronic acid (HA) is a natural and linear polymer that finds a wide-range of applications in medicine, cosmetics, and nutraceuticals because of excellent viscoelasticity, high moisture retention capacity, high biocompatibility and non-toxicity. HA has been recently produced in industrial scale by Streptococcal species. Streptococci are nutritionally fastidious lactic acid bacteria and cannot synthesize some amino acids. Therefore, it is necessary to study and select some commercial culture media for their growth. In this study, HA production and hyaluronidase activity of S. zooepidemicus ATCC 43079 in three culture media were investigated. Regarding the detrimental effect of this enzyme on HA amount, 6-O-Palmitoyl-L-ascorbic acid as hyaluronidase inhibitor was added to culture medium during fermentation. The effect of three variables consisted of glucose concentration, yeast extract concentration and medium pH each at 3 levels were considered and (response surface methodology (RSM) was used for statistical design of experiments to study the HA production by this strain. The results showed that maximum HA production was obtained when glucose concentration, yeast extract concentration and pH were 21.2 g L^-1, 43.6 g L^-1 and 6.6, respectively. Under optimum conditions, HA was produced as 370±15 mg L^-1 which was ~150% more than of HA concentration in basal medium (150±10 mg L^-1) and productivity reached 56.74 g L^-1 h^-1 that was increased 2 fold compared to central point.

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Nowadays, conversion industries with the objective of reducing production costs in the country are of great importance. On one hand, considering the high amount of waste after poultry slaughter in Iran, on the other hand, there are a lot of evidences related to the beneficial effects of hyaluronic acid on human health, especially in the treatment of joint diseases such as osteoarthritis. Many efforts have been carried out to make the best usage of these wastes. Therefore, the purpose of this study was to obtain the hyaluronic acid from rooster comb tissue with suitable physicochemical and rheological properties to enrich various foods, including dairy products. In this research, after the initial preparation of rooster comb tissue, hyaluronic acid was extracted through three methods using ultrasound waves-ethanol, physiological serum- acetic acid and physiological serum-ethanol solvents. Then, the physicochemical and rheological attributes of the acquired hyaluronic acid were evaluated. Based on findings, the highest content of extracted hyaluronic acid (4.2 mg/g) was determined in the presence of physiological serum-ethanol solvents (P<0.05). Also, the hydrocolloid was extracted through the mentioned method, had the highest brightness (23.74) and the lowest pH (6.76) and density (810 kg/m³) (P<0.05). However, the influence of different extraction methods on viscosity was insignificant (P>0.05). Hence, the results of the present study showed that the physiological serum-ethanol are an appropriate solvents for extracting and purifying hyaluronic acid, which could be used as a functional food additive.