Antibacterial activity and mechanism of astaxanthin crystals against Escherichia coli, Shewanella putrefaciens and its application in cooked pork preservation.

The objective of this work was to evaluate the antibacterial activity and mechanism of astaxanthin (AXT) crystals against Escherichia coli (E. coli) and Shewanella putrefaciens (S. putrefaciens). Scanning electron microscopy (SEM) showed that the bacteria after AXT action began to shrink, adhere, sag and other phenomena. The decrease of extracellular polysaccharide, the increase of protein content and conductivity, and FTIR analysis indicated that the action of AXT made the membrane protein structures change. Propidium iodide (PI) staining and fluorescence images revealed that the permeability of the cell membrane increased. The accumulation of reactive oxygen species (ROS) and apoptosis in E. coli and S. putrefaciens cells after AXT treatment indicated that AXT could lead to serious damage of the cells. These results could prove that AXT crystals could inhibit the bacteria growth by destroying bacterial biofilms, increasing cell membrane permeability, causing content outflow, and interfering with ROS mediated signaling. These results proved that the prospect utilization of AXT in food conservation as an antibacterial agent.