Effects of Dietary Bacillus natto Productive Protein on the Skin: In Vitro Efficacy Test and Single-Armed Trial

The dietary bacillus natto productive protein (BNPP) is a functional food ingredient that contains Bacillopeptidase F. BNPP is reported to improve blood flow. Based on previous research, we investigated the effect of BNPP on the skin. In vitro tests were performed to evaluate BNPP for its inhibitory effects on tyrosinase, elastase, and active oxygen (2,2-diphenyl-1-picrylhydrazyl (DPPH)) radical scavenging activities. In addition, a small-scale, single-armed trial of 15 female participants aged 40–65 years were conducted to assess the effects on human skin of BNPP, administered 250 mg/day orally, for 6 weeks. The beneficial effects of BNPP on the skin were shown by the evaluation of the tyrosinase inhibitory (0.01% and 0.1%), elastase inhibitory (0.00001% to 0.001%), and DPPH radical scavenging (1% and 10%) activities. In addition, the results suggested that the oral administration of BNPP may significantly enhance skin rosiness and also achieve significant improvement in skin conditions, defined as complexion, skin elasticity and resilience, moist feeling, skin texture, cosmetic adhesion, fine lines, under-eye darkness, eye bags, sagging cheeks, and sagging mouth. Furthermore, to investigate the use of BNPP as cosmetics, a skin irritation study was conducted using a cultured human skin model. The results showed that BNPP is non-irritant. In addition, to confirm the stability of BNPP, the quality of BNPP at the time of manufacture and three years and six months after manufacture was examined. The results showed no quality problems. These results suggest that the BNPP could be used as cosmetic purposes.