Antibacterial characteristics of orange pigment extracted from monascus pigments against Escherichia coli

Abstract

The antibacterial characteristics of orange pigment, which is one of the Monascus pigments, against Escherichia coli were investigated. Orange pigment exhibited strong antibacterial activity against E. coli evidenced by an increase in the diameter of inhibition zone with orange pigment treatment. The concentration of 2.5 mg/ml was the minimum inhibitory concentration of orange pigment against E. coli. Scanning electron microscopy revealed that orange pigment could damage bacterial cells, eventually resulting in cell death. The increase in the electric conductivity of bacterial cell suspensions suggested that the cytoplasmic membrane was broken by treatment with orange pigment. The result of orange pigment incorporation into egg PC further demonstrated the interaction between orange pigment and the phospholipid led to the disruption of bacterial membrane.