## 3 Results and Discussion
### Erythema, Melanin, and Lightness of the Dorsal Skin of Nude Mice  
Erythema and a* values are both indicators of the degree of skin inflammation [31], Figure 3A,B show the erythema and a* values in the dorsal skin of nude mice in each group. The initial erythema values of the dorsal skin ranged from 5.90 \(\pm\) 0.46 to 7.05 \(\pm\) 0.93, and the initial a* values ranged from 8.07 \(\pm\) 0.46 to 9.95 \(\pm\) 1.20. The two groups did not differ significantly (\(p\) > 0.05), suggesting that all animals were at the same baseline before induction. At week 8 of UVB irradiation, the erythema and a* values in the UVB group were significantly higher than those in the NC group by approximately 2.01 and 1.60, respectively, and at 13 weeks of irradiation, they were significantly higher than those in the NC group by 2.04 and 2.41, respectively. At week 13 of administering low, medium, and high doses of LPTWK10 or the spray-dried LPTWK10 supernatant, the mice exhibited significant reductions (\(p\) < 0.05) of approximately 1.73-2.53 and 1.85-2.99, respectively, in erythema values and approximately 2.20-3.23 and 2.41-3.79, respectively, in a* values relative to those in the UVB group mice. Figure 3: Effects of the administration of LPTWK10 or LPTWK10 spray-dried supernatant powders on dorsal (**A**) erythema (**B**) a* value (**C**) melanin and (**D**) lightness in UVB-induced nude mice. Data are presented as mean \(\pm\) SD (\(n\) = 7\(-\)8). Values with different uppercase letters were significantly different in the same weeks by [PERSON]’s multiple range test (\(p\) < 0.05). UVB: ultraviolet B; NC: normal control; PC: positive control; LPLD, LPLD and LPLD: administration of LPTWK10 viable cells at 2 \(\times\) 10\({}^{8}\) CFU/kg bw/day, 2 \(\times\) 10\({}^{9}\) CFU/kg bw/day and 2 \(\times\) 10\({}^{10}\) CFU/kg bw/day, respectively; SPLD, SPMD and SPHD: administration of LPTWK10 spray-dried supernatant powders at 0.30 g/kg bw/day, 0.60 g/kg bw/day, and 1.20 g/kg bw/day, respectively. Melanin is produced by melanocytes in the basal layer of the epidermis. Melancocytes can protect the skin by absorbing UV radiation. Prolonged exposure to UV radiation may lead to abnormal melanin accumulation, contributing to pigmentation and even the potential for other skin lesions [34; 35]. The initial melanin values ranged from 32.36 \(\pm\) 1.40 to 34.29 \(\pm\) 0.85, and the initial L* values ranged from 40.30 \(\pm\) 1.52 to 42.58 \(\pm\) 1.10 (Figure 3C,D). No significant difference (\(p>\) 0.05) was noted between the groups, suggesting that all animals were at the same baseline before induction. At week 12 of UVB irradiation, the melanin and L* values significantly increased by approximately 3.65 and decreased by approximately 2.45, respectively, in the UVB group compared with those in the NC group. At week 13 of irradiation, compared with the NC group, the UVB group exhibited significantly higher melanin value in the dorsal skin by approximately 2.44, and the L* value was significantly lower by approximately 3.20. In contrast, at week 13 of treatment with low, medium, and high doses of LPTWK10 or the spray-dried LPTWK10 supernatant, the mice exhibited significant decreases in melanin values of approximately 1.79-2.82 and 1.50-2.37, respectively, and significant increases in L* values of approximately 2.70-4.08 and 2.12-3.94, respectively, relative to those in the UVB group mice (\(p<\) 0.05). Studies by [PERSON] et al. (2022) and [PERSON] et al. (2015) indicate that LPTWK10 possesses antioxidant activity and inhibits melanin biosynthesis in melanocytes. Therefore, it is hypothesized that LPTWK10 can enhance the skin's antioxidant defenses against oxidative stress caused by UVB exposure. By reducing melanin production and improving overall skin tone, it may help prevent cellular damage and promote skin health [20; 36].