Preparation and Characterization of Rice Flour-based Starter Culture Powder Containing Enterococcus faecalis BD8: Antibacterial and Antioxidant Properties

Background: The development of natural starter cultures with antibacterial and antioxidant properties is gaining interest for improving food fermentation and safety. Enterococcus faecalis BD8, isolated from traditional fermented fish (bòo-doo), exhibits strong bioactivity. Methods: This study identified E. faecalis BD8 using MALDI-TOF mass spectrometry and assessed its antibacterial activity against Salmonella spp., Escherichia coli TISTR884, and Staphylococcus aureus TISTR512, as well as spoilage microorganisms. Antioxidant properties were measured using DPPH and ABTS assays. The bacterium was incorporated into rice flour-based starter culture powder via freeze-drying. Viability during storage and its application in fermented fish (Pla Som) were evaluated, along with sensory attributes. Results: E. faecalis BD8 exhibited significant antibacterial activity, with inhibition zones ranging from 16 to 22 mm, particularly against S. aureus (p < 0.05). Antioxidant activity was moderate, with IC50 values of 0.45 mg/mL (DPPH) and 0.32 mg/mL (ABTS). The starter culture powder retained 82% bacterial viability after 30 days at 4°C. When applied in Pla Som, fermentation was completed in 48 hours, reducing traditional processing time. Sensory evaluation showed favorable ratings for appearance and aroma, though texture required optimization. Conclusion: The rice flour-based E. faecalis BD8 starter culture demonstrates potential for fermented food applications, enhancing safety and efficiency. Further optimization is needed to improve sensory characteristics.