Effects of Fucoidan on the Inhibition of Biofilm Formation of Salmonella enterica Subsp. enterica Serovar Typhimurium on Seafoods and Its Molecular Antibiofilm Mechanisms

Abstract

Foodborne illnesses, particularly those caused by Salmonella enterica subsp. enterica Serovar Typhimurium, present a significant challenge to public health, especially within the seafood industry due to biofilm formation on foods. This study investigated the antibiofilm potential of fucoidan, a sulfated polysaccharide, against Salmonella enterica subsp. enterica Serovar Typhimurium biofilm on crab and shrimp surfaces. Fucoidan's minimum inhibitory concentration (MIC) was determined to be 150 µg/mL. Sub-MIC (1/8, 1/4, 1/2, and MIC) were evaluated for their impact on inhibition of biofilm formation. Fucoidan treatment resulted in significant, dose-dependent inhibition in biofilm formation, achieving 2.61 log CFU/cm² and 2.45 log CFU/cm² reductions on crab and shrimp surfaces, respectively. FE-SEM analysis confirmed biofilm disruption and cell membrane damage. Real-time PCR showed the downregulation of quorum-sensing (luxS) and virulence (rpoS, avrA, and hilA) genes. These results propose that fucoidan has the ability as a natural antibacterial agent for controlling Salmonella enterica subsp. enterica Serovar Typhimurium biofilms in seafood processing, thereby enhancing food safety and minimizing contamination.

Keywords: Salmonella enterica subsp. enterica Serovar Typhimurium; biofilms; crab shells; fucoidan; shrimp shells.

Figure 1

Minimum inhibitory concentrations of Fucoidan against S. Typhimurium ATCC 13311. Data are presented as mean ± SEM from three independent experiments. Within each treatment, values with different letters (a–g) indicate significant differences according to Duncan’s multiple range test (p < 0.05).

Figure 2

Biofilm formation by S. Typhimurium ATCC 13311 on crab coupons in the presence of sub-MIC of fucoidan (0, 1/8, 1/4, 1/2, and MIC) under optimal conditions (37 °C, pH 7.0). Data are expressed as mean ± SEM from three independent replicates. Within each treatment, values with different letters (a–d) indicate significant differences according to Duncan’s multiple range test (p < 0.05).

Figure 3

Biofilm formation by S. Typhimurium ATCC 13311 on shrimp coupons in the presence of sub-MIC of fucoidan (0, 1/8, 1/4, 1/2, and MIC) under optimal conditions (37 °C, pH 7.0). Data are expressed as mean ± SEM from three independent replicates. Within each treatment, values with different letters (a–e) indicate significant differences according to Duncan’s multiple range test (p < 0.05).

Figure 4

Representative scanning electron micrographs of S. Typhimurium ATCC 13311 biofilm formation on crabs and shrimp under optimal conditions in the presence of different sub-MIC concentrations of fucoidan: (A) control; (B) 1/8 MIC; (C) 1/2 MIC for crabs, and (D) control; (E) 1/8 MIC; (F) 1/2 MIC for shrimp.

Figure 5

Relative expression levels of rpoS, avrA, hilA, and luxS genes in S. Typhimurium ATCC 13311 suspension supplemented with different concentrations of fucoidan. Different superscript letters (a, b) indicate significant differences (p < 0.05) based on three independent replicates.