Antimicrobial effect and mechanism of non-antibiotic alkyl gallates against Pseudomonas fluorescens on the surface of Russian sturgeon (Acipenser gueldenstaedti)

Abstract

Since Pseudomonas fluorescens is the main microorganism causing severe spoilage in refrigerated aquatic products, the searching for non-antibiotic antibacterial agents effective against it continues to receive increasing interest. This study aimed to investigate the antibacterial effects and mechanisms of alkyl gallic esters against P. fluorescens isolated from the Russian sturgeon (Acipenser gueldenstaedti), as well as the effectiveness in combination with chitosan films on the preservation of sturgeon meats at 4 °C. Our data shows that the alkyl chain length plays a significant role in eliciting their antibacterial activities and octyl gallate (GAC8) exhibited an outstanding inhibitory efficacy. GAC8 can rapidly enter into the membrane lipid bilayer portion to disorder the membrane, and further inhibit the growth of the P. fluorescens through interfering both tricarboxylic acid cycle related to energy supply and amino acid metabolism associated with cell membranes, suppressing oxygen consumption and disturbing the respiration chain. Moreover, the alteration in membrane fatty acids indicated that GAC8 could disrupt the composition of cell membrane fatty acids, rendering the bacteria more sensitive to the antibacterial. The SEM results also substantiate the damage of the structure of the bacterial membrane caused by GAC8. Additionally, the edible chitosan-based films incorporated with GAC8 showed the enhanced antibacterial efficacy to remarkably extend the shelf life of Russian sturgeon. Overall, our findings not only provide new insight into the mode of action of GAC8 against P. fluorescens but also demonstrate composite films containing GAC8, as a kind of safe and antibacterial material, have a great promise for application in food preservations.

Keywords: Alkyl gallates; Antibacterial; Chitosan-based films; Membrane fatty acids; Metabolism analysis; Pseudomonas fluorescens.