Synergistic bactericidal action of phytic acid and sodium chloride against Escherichia coli O157: H7 cells protected by a biofilm

Nam Hee Kim, Min-Suk Rhee

Research output: Contribution to journalArticle

12 Citations (Scopus)


The food industry must prevent the build-up of strong Escherichia coli O157:H7 biofilms in food processing environments. The present study examined the bactericidal action of phytic acid (PA), a natural extract from rice bran and the hulls/peels of legumes, against E. coli O157:H7 biofilms. The synergistic bactericidal effects of PA plus sodium chloride (NaCl) were also examined. E. coli O157:H7 biofilms were allowed for form on stainless steel coupons by culture in both rich (tryptic soy broth, TSB) and minimal (M9) medium at 22 °C for 6 days. Bacterial cells within biofilms grown in M9 medium were significantly more resistant to PA than those grown in TSB (p <0.05); thus M9 medium was selected for further experiments. The anti-biofilm effect of PA was significantly increased by addition of NaCl (2-4%) (p <0.05); indeed, the combination of 0.4% PA plus 3-4% NaCl completely inactivated E. coli O157:H7 biofilms without recovery (a > 6.5 log CFU/cm2 reduction). Neither PA nor NaCl alone were this effective (PA, 1.6-2.7 log CFU/cm2 reduction; NaCl, 2 reduction). Confocal laser scanning microscopy images of propidium iodide-treated cells showed that PA (0.4%) plus NaCl (2-4%) had marked membrane permeabilizing effects. These results suggest that a sanitizer that combines these two naturally occurring antimicrobial agents may be useful to food safety managers who encounter thick biofilm formation in food processing environments.

Original languageEnglish
Pages (from-to)17-21
Number of pages5
JournalInternational Journal of Food Microbiology
Publication statusPublished - 2016 Jun 16



  • Biofilm
  • Control
  • Escherichia coli O157:H7
  • Phytic acid
  • Sodium chloride

ASJC Scopus subject areas

  • Food Science
  • Microbiology
  • Safety, Risk, Reliability and Quality

Cite this