Fermentation Preparation of Camellia Seed Peptides and Their Antioxidant and Hyaluronidase Inhibitory Activities

Camellia seed cake is an underutilized by-product derived from the Camellia oil refining process, which is a rich source of plant proteins that has not yet been fully exploited. In this study, Camellia seed cake was employed as the raw material for the production of Camellia seed peptides through microbial fermentation. The Bacillus subtilis CGMCC NO. 29154 strain was identified as the optimum fermentation strain for Camellia seed peptides by evaluating the peptide yield and antioxidant activity of the fermentation products. An orthogonal experiment was conducted to optimize the fermentation parameters of the peptides in a 5 L bioreactor. The results demonstrated that the highest peptide yield of 12.15% was achieved following 22 h of fermentation at a substrate concentration of 30 g/L Camellia seed cake powder (60 mesh), 4 g/L sucrose, a fermentation rotational speed of 180 r/min, a liquid loading rate of 50%, an aeration volume of 0.30 vvm (the aeration rate for 1 min was 0.30 times the volume of the fermentation broth), and an inoculum volume of 19%. Furthermore, the fermented Camellia seed peptides demonstrated notable antioxidant and hyaluronidase inhibitory activities. The IC₅₀ values for DPPH, ABTS⁺ and hydroxyl radical scavenging were 1.18, 0.65 and 1.18 mg/mL for shake flask culture and 0.72, 0.52 and 0.85 mg/mL for bioreactor culture, respectively. The IC₅₀ values for hyaluronidase inhibition were 4.58 mg/mL for shake flask culture and 4.17 mg/mL for bioreactor culture. All of these values were significantly (P < 0.05) superior to those of unfermented Camellia seed cake. The present study indicated that Bacillus subtilis CGMCC NO. 29154 had good application potential for preparing bioactive peptides from fermented Camellia seed cake. Further optimization of the fermentation process, including scale-up, could enhance the yield and quality of these peptides, which could in turn lay a scientific foundation for the high-value utilization of Camellia seed cake and the industrial production of Camellia seed peptides.