De novo synthesis of hyaluronic acid with tailored molecular weights using a new hyaluronidase SthHL

Hyaluronic acid (HA) exhibits various biological activities and functions, mainly governed by its molecular weight (M_W). Traditional HA degradation methods encounter challenges such as environmental pollution and high costs. Thus, developing a safe cell factory with an efficient regulation strategy for one-step production of specific M_W HA has attracted significant research interest. This study identified a new hyaluronidase, SthHL (approximately 21.9 kDa), from a microbial species. Additionally, SthHL was characterized, with R188 and V192 as key catalytic amino acids and no activity towards mannan and chondroitin sulfate. Subsequently, SthHL was introduced into Bacillus amyloliquefaciens SE-StAB, known for high M_W HA production. By modulating expression, four different M_W HAs were obtained and characterized. HAs are non-Newtonian fluids, and their free radical scavenging capacity increases linearly as the M_W decreases. Significantly, HA oligosaccharides can promote intestinal health and exert a prebiotic effect. Therefore, this study offers a new strategy for synthesizing tailored M_W HAs and valuable insights for exploring structure-effect relationships in various applications.