Fermentation of rose residue by Lactiplantibacillus plantarum B7 and Bacillus subtilis natto promotes polyphenol content and beneficial bioactivity

The present study evaluated the effect of fermentation with Lactiplantibacillus plantarum B7 and Bacillus subtilis natto on phenolic compound levels and enzyme activity, as well as antioxidant capacity of the rose residue. Results showed that the polyphenol content of rose residue was significantly increased from 16.37 ± 1.51 mg/100 mL to 41.02 ± 1.68 mg/100 mL by fermentation at 37 °C and 2.0% (v/v) inoculum size for 40 h. The flavone, soluble dietary, and protein contents were also enhanced by almost 1-fold, 3-fold, and 1-fold, respectively. Fifteen phenolic compounds were quantified in the fermented broth, among which the concentration of gallic acid, quercetin, and p-coumaric acid increased by 5-fold, 4-fold, and almost 8-fold, respectively. Chlorogenic acid was a new phenolic compound produced during fermentation. Moreover, the fermented rose residue presented higher superoxide dismutase, α-amylase, and protease activity. ABTS•+, hydroxylradical, and DPPH• scavenging activity increased by 60.93%, 57.70%, and 37.00%, respectively. This provides an effective means of transforming rose residue into a highly bioactive value-added substance.