Characterization of keratinase from Chryseobacterium camelliae Dolsongi-HT1 and efficacy on skin exfoliation

Keratin is the outermost layer that protects our skin and has an appropriate turnover cycle. With age, the keratin turnover cycle begins to dysfunction. To overcome this issue, we artificially remove dead skin cells. In this study, we attempted to screen enzymes that could be useful in the cosmetics industry to develop enzymes suitable for the enzyme-based method, a mild exfoliation method that does not damage the skin. Chryseobacterium camelliae Dolsongi-HT1 with keratinolytic activity was isolated from green tea leaves (sourced from the Dolsongi tea garden, Jeju Island). The keratinolytic activity of C. camelliae Dolsongi-HT1 was detected in the culture media, indicating that the target keratinolytic enzyme is a secreted protein. Keratinolytic activity was demonstrated using forearm skin keratin and reconstituted human skin models. The enzyme from C. camelliae Dolsng-HT1 (HT1) could efficiently decompose human skin keratin. Moreover, experiments using the reconstituted human skin model demonstrated that HT1 is efficient in exfoliating the outermost stratum corneum. Compared with the popularly used chemical exfoliation method, enzymatic exfoliation using HT1 was less abrasive and did not damage the epidermal layer. Keratinolytic enzyme was identified using protein purification and mass spectrometry. The identified enzyme (iHT1) was expressed in the Bacillus subtilis RIK 1285 secretory protein expression system. The iHT1 enzyme showed high activity over a wide temperature range (30-60 °C), with the highest activity at 30 °C. The optimum pH for the activity of iHT was pH8.