29F-12 |
Antimicrobial effectiveness of sodium hexametaphosphate with lysozyme against Escherichia coli O157:H7 |
J. BOLAND1, P. M. Davidson2, and J. Weiss2. (1) Colloidal and Interfacial Food Science Laboratory, University of Tennessee, 2605 River Drive, Room 102, Knoxville, TN 37996, (2) Dept. of Food Science & Technology, Univ. of Tennessee, 2509 River Dr., 201 Mcleod Food Tech Bldg., Knoxville, TN 37966-4539 Polypeptide antimicrobials, e.g., lysozyme, have enhanced antimicrobial activity when used with chelators. Sodium hexametaphosphates (SHMP) are approved for fruit juice preservation and exhibit chelating properties. They may serve as GRAS compounds to improve antimicrobial activity against E. coli O157:H7. The objective of this study was to compare the effect of SHMP, disodium pyrophosphate (DSPP) and disodium tripolyphosphate (DSTPP) on antimicrobial efficacy of lysozyme against E. coli O157:H7. Lysozyme (200-600 µg/mL) was added to 3,000–15,000 µg/mL DSPP, DSTPP and 3 commercial SHMPs (Glass H® (1800 Da) Sodaphos® (1437 Da) Hexaphos® (1285 Da). A microbroth dilution assay was used to study the activity of lysozyme/chelator combinations against E. coli O157:H7 at pH 6-8 by monitoring OD over 48 hr. 10,000 µg/mL DSPP and 200 µg/mL lysozyme inhibited strains 932 and H1730 at pH 6. Similarly, 10,000 µg/mL DSTPP and 200 µg/mL lysozyme inhibited strain 932. Inhibition of H1730 at pH 8 was found at 5,000 µg/mL DSTPP. The commercial SHMPs inhibited strain 932 for only 6 hr but growth occurred after 12 hr at pH 6, 7, or 8. Molecular weight of SHMP did not influence inhibition. The greatest inhibition by the SHMPs occurred with strain H1730 where no growth occurred for 12 hr at 3,000 µg/mL (pH 6, 7, or 8). Results indicate that SHMPs were not as effective as DSPP or DSTPP on an equal concentration basis at inhibiting E. coli O157:H7. Results could be explained by the lower chemical potential of the SHMPs compared to the chelating activities of DSTPP or DSPP. Results indicate that chemical properties of chelators play an important role in increasing the antimicrobial activity of lysozyme against Gram-negative pathogens.
Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
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