Antimicrobial activities of ethanolic Kiam (Cotyleobium lanceotatum) wood extract and its application to extend shelf life of refrigerated Pacific white shrimp

Kiam wood has been well-known as a natural food preservative in Thailand. Nevertheless, antimicrobial properties against spoilage bacteria as well as their application to extend seafood shelf life remain unclear. Therefore, the present study aimed to investigate antimicrobial activities, active compounds responsible for the antimicrobial activities, and their effect on refrigerated white shrimp shelf life. The result showed that ethanolic Kiam wood extract (eKWE) exhibited strong antibacterial activities against Staphylococcus aureus PSU.SCB.16S.41, Shewanella putrefaciens JCM20190, and Shewanella sp. TBRC 5775. Among these tested bacteria, the strongest antimicrobial activity was observed against S. aureus, with MIC and MBC at 32 µg/mL and 128 µg/mL, respectively. The eKWE showed effectiveness in inhibiting bacterial biofilm formation and motility, as well as cell deformities as witnessed by cell-wall damages with numerous pores on the cell surfaces (based on scanning electron microscopic images). When applied in refrigerated white shrimp, eKWE reduces the growth of mesophilic bacteria, psychrophilic bacteria, Pseudomonas, total coliform, and Shewanella counts. The LC/MS analysis revealed that Vaticanol B was the predominant compound and likely played a role in inhibiting bacterial growth in the refrigerated shrimp meat.