Identification and antioxidant activity of hyaluronic acid extracted from local isolates of Streptococcus thermophilus

Abstract

The synthesis of hyaluronic acid (HA) by bacteria is a promising alternative to extracting the biopolymer from animal tissues. The production of HA by Streptococcus thermophilus, which belongs to the group of organisms generally recognized as safe (GRAS), is a well-studied viable alternative. The present study investigated five S. thermophilus strains (St1, St2, St3, St4, and St5) with markedly high HA productivity. The quantity of purified HA was different following the order St5 > St4 > St3 > St2 > St1. The characteristics of molecular mass analysis of HAs were evaluated by multi-technique (FTIR, NMR, and HPLC). The antioxidant activity of the purified HA was quantified by multi-technique (DPPH, iron chelating, reducing power, and hydrogen peroxide (H2O2) scavenging activity), over a range of relevant concentrations, i.e., 50, 100, 300, 500, 700, 1100, and 1300 µg/ml. They were tested for a concentration-dependent enhancement in their radical scavenging and lowering abilities. Significantly increased antioxidant activity was detected at concentrations of 1300 µg/ml, with 69.18%, 78.42%, and 73.74% of DPPH, hydrogen peroxide, and iron-chelating scavenging activities, respectively. Furthermore, HA was proven to have effective lowering power at the same concentration. When compared to the typical antioxidant Butylated hydroxytoluene (BHT), but these various antioxidant activities were low. It is suggested that HA have the potential to be the resource of natural antioxidant.