Optimization of Mixed-Culture Solid-State Fermentation and the Effect of Microencapsulation on the Antioxidant...

Cherry blossom extract (CBE) is rich in natural antioxidants; however, the poor release of bound bioactive compounds and the instability of the extract itself limit its further application. This study aimed to improve the antioxidant activity and stability of CBE by combining mixed-culture solid-state fermentation with microencapsulation. Using total phenolic content (TPC) as the primary response variable, we optimized the solid-state fermentation conditions for a mixed culture of Bacillus subtilis and Monascus purpureus via single-factor experiments combined with the Box-Behnken response surface method. Extracts prepared under these optimal conditions were then microencapsulated using a gelatin-chitosan co-precipitation method, and their antioxidant activity and in vitro release behavior were evaluated. The optimal fermentation conditions were an inoculation amount of 10.5%, an inoculation proportion of 1.3:1 (w/w), and a fermentation time of 7.3 days, producing a total phenolic content (TPC) of 38.49 ± 0.41 mg gallic acid equivalent (GAE)/g dry weight (DW). After 150 h, the micro-capsules had released 49.6% of their bioactive contents, with 50.4% remaining encapsulated. Collectively, these findings demonstrate that the mixed-culture fermentation extract exhibited higher antioxidant activity than both the single-strain extract and the non-fermented control, thereby overcoming key application bottlenecks of CBE.