Bacterial cellulose (BC) is limited in active food packaging applications due to its lack of antioxidant and antibacterial activities. To endow BC with these functions, an engineered strain of Komagataeibacter nataicola, designated Kn-pTyr1-Bm, was constructed by introducing a tyrosinase gene, and it was used to ferment eumelanin-loaded bacterial cellulose (Eum-BC). Using the relative eumelanin accumulation rate as the indicator, the fermentation process was optimized by response surface methodology. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to analyze the structural characteristics, and the changes in antioxidant activity, antibacterial activity, and cherry tomato preservation performance before and after eumelanin loading were evaluated through in vitro experiments. The results showed that the optimal fermentation conditions were as follows: pH 8.7, tyrosine concentration 0.6 g·L?¹, temperature 35 °C, copper ion concentration 10 μmol·L?¹, shaking speed 90 r·min?¹, PBS dilution factor 1×, and melanin buffer addition volume 30 mL. Under these conditions, the relative eumelanin accumulation rate reached 2.54×10?² h?¹, which was 67.37% higher than that under the initial conditions. SEM and FTIR results confirmed that eumelanin was successfully loaded. At 2.3 mg·mL?¹, the scavenging rates of Eum-BC against hydroxyl radicals, DPPH radicals, and superoxide anion radicals were 91.25%, 92.16%, and 89.16%, respectively, and the inhibition zone diameters against Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes were also increased by 8.89, 8.87, and 5.83 mm, respectively, compared with the BC control group. Cherry tomato preservation experiments showed that the Eum-BC film effectively delayed fruit weight loss, softening, and post-ripening senescence, and prolonged the storage life of the fruit. In summary, the engineered strain and optimized fermentation process developed in this study can effectively prepare eumelanin-loaded bacterial cellulose, and its antibacterial and antioxidant activities provide theoretical support for the application of BC in the field of food preservation.