The aqueous extracts of Citrus unshiu peel containing flavonoid glycosides was used as co-substrate with Schizophyllum commune mycelia producing β-glucosidase and its biological activities were studied. β-glucosidase-produced S. commune mycelia converted the glycosides (narirutin and hesperidin) into aglycones (naringenin and hesperetin). The photoprotective potential of fermented C. unshiu peel extract with S. commune (S-CPE) was tested in human dermal fibroblasts (HDFs) exposed to UVA. It was revealed that S-CPE had an inhibitory effect on human interstitial collagenase (matrix metalloproteinase, MMP-1) expression in UVA-irradiated HDFs. The treatment of UVA-irradiated HDFs with S-CPE resulted in a dose-dependent decrease in the expression level of MMP-1 mRNA. The UVA irradiation raised the proportion of senescence-associated β-galactosidase (SA-β-gal) positive cells in comparison with the normal control group. The treatment of UVA-irradiated HDFs with S-CPE was shown to decrease the level of SA-β-gal (by approximately 45% at an S-CPE concentration 0.1%, w/v) compared with the UVA-irradiated HDFs. It was found that S-CPE containing hesperetin has notable collagen biosynthetic activity for fibroblasts, indicating that S-CPE can be promising cosmetic ingredients. Copyright © 2012 John Wiley & Sons, Ltd.