Anti-biofilm effect of enzymatic hydrolysates of ovomucin in Listeria monocytogenes and Staphylococcus aureus.

Despite modern advances in food hygiene, food poisoning due to microbial contamination remains a global problem, and poses a great threat to human health. Especially, Listeria monocytogenes and Staphylococcus aureus are gram-positive bacteria found on food-contact surfaces with biofilms. These foodborne pathogens cause a considerable number of food poisoning and infections annually. Ovomucin (OM) is a water-insoluble gel-type glycoprotein in egg whites. Enzymatic hydrolysis can be used to improve the bioactive properties of OM. This study aimed to investigate whether ovomucin hydrolysates (OMHs) produced using five commercial enzymes (Alcalase®, Bromelain, α-Chymotrypsin, Papain, and Pancreatin) can inhibit the biofilm formation of L. monocytogenes ATCC 15313, L. monocytogenes H7962, S. aureus KCCM 11593, and S. aureus 7. Particularly, OMH prepared with papain (OMPP; 500 µg/mL) significantly inhibited biofilm formation in L. monocytogenes ATCC 15313, L. monocytogenes H7962, S. aureus KCCM 11593, and S. aureus 7 by 85.56 %, 80.28 %, 91.70 %, and 79.00 %, respectively. In addition, OMPP reduced the metabolic activity, exopolysaccharide production (EPS), adhesion ability, and gene expression associated with the biofilm formation of these bacterial strains. These results suggest that OMH, especially OMPP, exerts anti-biofilm effects against L. monocytogenes and S. aureus. Therefore, OMPP can be used as a natural anti-biofilm agent to control food poisoning in the food industry.

Immunostimulatory Effect of Ovomucin Hydrolysates by Pancreatin in RAW 264.7 Macrophages via Mitogen-Activated Protein Kinase (MAPK) Signaling Pathway.

Ovomucin (OM), which has insoluble fractions is a viscous glycoprotein, found in egg albumin. Enzymatic hydrolysates of OM have water solubility and bioactive properties. This study investigated that the immunostimulatory effects of OM hydrolysates (OMHs) obtained by using various proteolytic enzymes (Alcalase®, bromelain, α-chymotrypsin, Neutrase®, pancreatin, papain, Protamax®, and trypsin) in RAW 264.7 cells. The results showed that OMH prepared with pancreatin (OMPA) produced the highest levels of nitrite oxide in RAW 264.7 cells, through upregulation of inducible nitric oxide synthase mRNA expression. The production of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-6 were increased with the cytokines mRNA expression. The effect of OMPA on mitogen-activated protein kinase signaling pathway was increased the phosphorylation of p38, c-Jun NH2-terminal kinase, and extracellular signal-regulated kinase in a concentration-dependent manner. Therefore, OMPA could be used as a potential immune-stimulating agent in the functional food industry.