Abstract:Chicken bone was fermented with?Bacillus?subtilis?to produce antioxidant peptides，which aimed to improve the utilization value of animal processing by-products and develop value-added products. The OD value was adopted to examine the effect of glucose addition on the growth of?B.subtilis.The antioxidant activity and hydrolysis degree were used to evaluate the effects of fermentation conditions（chicken bone meal addition amount，initial medium pH，bacterial inoculum amount，liquid loading volume，and incubation time）on the preparation of antioxidant peptides from chicken bone by single factor experiments.Furthermore，the fermentation conditions were optimized by response surface design with the antioxidant activity as the evaluation indicator. The fermentation broth was separated by organic membrane，and the antioxidant activities of the components with different molecular weights were determined.Scanning electron microscopy（SEM）was employed to observe the changes in the morphology and structure of chicken bone before and after fermentation.The results showed that the growth of?B.?subtilis?was enhanced in the absence of glucose in the medium. The optimal fermentation conditions were determined as follows：chicken bone meal addition amount of 3.2%，initial medium pH6，bacterial inoculum amount of 4.0%，liquid loading volume of 59 mL/250 mL，and incubation for 20 h.The antioxidant peptide prepared under these conditions showed the DPPH free radical scavenging rate of 69.55% and the hydrolysis degree of 77.93%. Among the fractions obtained after membrane separation，the peptides with molecular weights of 1-10 kDa showed strong antioxidant activity，with the DPPH free radical scavenging rate above 50%，the ABTS+free radical scavenging rate above 89%，and the pyrogallic acid autoxidation rate above 20%. The SEM results revealed that the chicken bone presented changed morphology and structure after fermentation，with concave and broken surface，which indicated that the chicken bone had been hydrolyzed.