Microorganisms and culture
A total of four food-related bacteria were kindly provided by the Culture Collection of Department of Microbiology,
Faculty of Science, King Mongkut’s University of Technology Thonburi. They are two Grampositive bacteria (B. subtilis and S. aureus) and two Gram-negative bacteria (E. coli and S. typhimurium). The strains were maintained at 4 °C in Mueller Hinton agar slants. Before experimental use, cultures from solid media were sub-cultivated in Mueller Hinton broth, incubated for 24 h at 37 °C, and used as the inocula for the determination of antibacterial activity