Antimicrobial properties of milkfat globule membrane fractions.
Milkfat globule membranes (MFGMs) were prepared from bovine cream according to standard procedures. These membranes and peptide hydrolysates, which were generated by proteolysis with immobilized digestive enzymes, were screened for antibacterial activity against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica Typhimurium, Pseudomonas fluorescens, Bacillus cereus, Lactobacillus acidophilus, and Lactobacillus gasseri. Assays were first performed on beef heart infusion (BHI) plates spotted with test protein-peptide fractions and then seeded with lawns of indicator cells to monitor the zone of growth inhibition. Under these experimental conditions, MFGMs were most active against Salmonella Typhimurium and P. fluorescens. However, antibacterial activity was not seen after plating on Luria-Bertani (LB) medium. We determined that the antimicrobial effects observed on BHI plates were due to the generation of H2O2 by xanthine oxidase, a major protein constituent of the MFGMs, as a result of purine catalysis. This substrate is present in BHI but lacking in LB medium. Evaluation of purified xanthine oxidase alone resulted in analogous data trends. The growth of probiotic Lactobacillus strains were affected only marginally when grown on lactobacilli deMan Rogosa Sharpe plates, suggesting the decreased sensitivity of these bacteria to H2O2. In this study, several MFGM hydrolysates exhibited variable antibacterial activity against test food pathogens on agar plates prepared with M9 minimal media, and this variation was not attributable to xanthine oxidase enzymatic activity. The probiotic microorganisms were mostly resilient to these antibacterial fractions. Bovine MFGM fractions may represent an excellent resource material from which to generate native, naturally occurring biodefensive proteins and/or peptides.
Clare
Debra A
DA
Department of Food Science, Southeast Dairy Foods Research Center, North Carolina State University, Raleigh, North Carolina 27695-7624, USA. debra_clare@ncsu.edu
Zheng
Zuoxing
Z
Hassan
Hosni M
HM
Swaisgood
Harold E
HE
Catignani
George L
GL
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001409:Bacillus cereus / Q000254:growth & development; D002417:Cattle; D003257:Consumer Product Safety; D003470:Culture Media / Q000737:chemistry; D019453:Escherichia coli O157 / Q000254:growth & development; D005506:Food Contamination / Q000517:prevention & control; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007778:Lactobacillus / Q000254:growth & development; D008565:Membrane Proteins / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000737:chemistry*; D011492:Protein Hydrolysates / Q000494:pharmacology*; D011551:Pseudomonas fluorescens / Q000254:growth & development; D012486:Salmonella typhimurium / Q000254:growth & development
D000900:Anti-Bacterial Agents; D003470:Culture Media; D005520:Food Preservatives; D008565:Membrane Proteins; D011492:Protein Hydrolysates; D006861:Hydrogen Peroxide