Effects of fermentation conditions and soybean peptide supplementation on hyaluronic acid production by Streptococcus thermophilus strain YIT 2084 in milk.

To increase the hyaluronic acid (HA) yield from Streptococcus thermophilus YIT 2084, fermentation conditions (pH, temperature, agitation, aeration) were optimized in milk-based medium, and the effects of supplemental soybean peptides, which have different molecular weight distributions, were determined. HA production was enhanced to approximately 100 mg/l at pH 6.8 and 33-40 degrees C. Agitation speed and aeration rate slightly affected HA production. Soybean peptides including those of high molecular weight (approximately 27 to 130 kDa) further increased HA production to 208 mg/l under the optimal condition (pH 6.8, 35 degrees C, 100 rpm), which was 20-fold greater than non-optimal condition. HA production was no longer related to the specific growth rate. The HA produced under the optimal condition included a large amount of high-molecular-weight fraction of 100 to 2000 kDa, compared with under the basal condition without optimization.

Streptococcus thermophilus produces exopolysaccharides including hyaluronic acid.

Hyaluronic acid (HA) is an important material for medical, cosmetic and food applications. HA is obtained commercially from rooster combs and the fermentation of streptococci. However, the safety problems such as hyaluronidase or exotoxin contamination remain controversial. To reduce the risk of hyaluronidase or exotoxin contamination, we attempted to isolate strains of Streptococcus thermophilus with high productivity of useful exopolysaccharides (EPSs) including HA from traditional dairy food products. Forty-six S. thermophilus strains were isolated from dairy food products, and examined of their HA production using a HA binding protein method. According to the results, six S. thermophilus strains produced EPSs including HA. S. thermophilus YIT 2084 had a markedly high HA productivity (approximately 8 mg/l). We focused on the high-molecular-mass fraction of EPS (2000 kDa) from S. thermophilus YIT 2084. By using high-performance liquid chromatography, it was found that a high-molecular-mass fraction of EPS included N-acetylglucosamine (54.4%) and glucuronic acid (45.6%), which are components of HA. Furthermore, 13C-nuclear magnetic resonance spectroscopy showed that the spectra of the high-molecular-mass fraction corresponded well to those of commercial HA. Here, we described for the first time that S. thermophilus, which is a generally recognized safe bacterium, produces HA. The novel HA-producing bacterium S thermophilus YIT 2084 has great potential for applications in the medical, cosmetic and food fields, although its culture conditions remain to be improved.

Topical application of Bifidobacterium-fermented soy milk extract containing genistein and daidzein improves rheological and physiological properties of skin.

The authors examined the effects of Bifidobacterium-fermented soy milk extract (BE) containing genistein and daidzein on the hyaluronic acid (HA) content and rheological and physiological properties of hairless mouse and/or human skin. Topical application of BE for six weeks significantly restored changes in the elasticity and viscoelasticity of mouse skin, increased the HA content, and hydrated and thickened mouse skin. Also, topical application of a gel formula containing 10% BE to the human forearm for three months significantly lessened the decrease in skin elasticity. Therefore, BE is expected to become a new cosmetic ingredient to prevent the loss of skin elasticity through enhancement of HA production.

Genistein and daidzein stimulate hyaluronic acid production in transformed human keratinocyte culture and hairless mouse skin.

We examined the effects of the soy isoflavones genistein (Gen) and daidzein (Dai) on the production of hyaluronic acid (HA) in a transformed human keratinocyte culture and in hairless mouse skin following topical application for 2 weeks. Gen and Dai, but not the glycosides thereof, significantly enhanced the production of HA in vitro and in vivo. Histochemistry using an HA-binding protein revealed that topical Gen and estradiol raised both the density and intensity of HA staining, which was abundant in the murine dermis. It is suggested that Gen and Dai are not released from their respective glycosides in culture or murine skin. Moreover, topical Gen and Dai may prevent and improve the cutaneous alterations caused by the loss of HA in skin.