Antimicrobial Effects of Olive Pomace Extract and UV-A Light

Antimicrobial Synergy of Olive Pomace Extract and UV-A Light

The increasing prevalence of bacterial pathogens in food handling and processing environments necessitates innovative and effective antimicrobial strategies. Traditional methods often rely on chemical sanitizers, which can leave harmful residues and have limited effects on biofilms. Recent studies have highlighted the potential of plant-derived extracts, specifically olive pomace extract (OPE), in conjunction with non-thermal technologies like UV-A light to enhance antimicrobial efficacy.

In a study examining the antimicrobial effects of OPE and UV-A light, it was found that the combination exhibited strong synergistic activities against common foodborne pathogens such as Escherichia coli O157:H7 and Listeria innocua. The interaction index calculated using isobologram analysis indicated a significant synergistic effect (γ < 1), achieving over 5-log reductions in bacterial populations within 30 minutes of treatment. Notably, the phenolic compounds within OPE, particularly 4-hydroxyphenylacetic acid and hydroxytyrosol, were identified as critical contributors to this enhanced antimicrobial activity.

The antimicrobial mechanism underlying this synergy is primarily attributed to oxidative stress induction, membrane damage, and metabolic inhibition, which disrupt bacterial cell integrity and function. This innovative approach suggests a promising alternative to conventional sanitizers, utilizing agricultural byproducts to enhance microbial safety in food processing environments.

Mechanisms Behind the Enhanced Efficacy Against Bacterial Pathogens

The mechanisms underlying the enhanced efficacy of the combined treatment of OPE and UV-A light can be explained through several key processes:

1. Oxidative Stress Induction: The combined treatment significantly increased the levels of reactive oxygen species (ROS) within bacterial cells, leading to oxidative damage of cellular components, including proteins and lipids. This was evidenced by decreased intracellular thiol content and increased membrane permeability as measured by SYTOX Orange staining.

2. Membrane Damage: The synergistic effect of OPE and UV-A light resulted in compromised membrane integrity, leading to increased permeability that allows for the passage of fluorescent dyes, indicating cellular damage. The SMP assay demonstrated a significant increase in membrane-damaged cells after combined treatment compared to individual treatments.

3. Inhibition of Metabolic Activities: The combined treatment also inhibited metabolic activities in bacterial cells, as observed through resazurin-based metabolic assays. This treatment significantly delayed the recovery of metabolic functions in E. coli and L. innocua, indicating profound effects on cellular metabolism.

These mechanisms highlight the multifaceted approach of using OPE and UV-A light, which not only disrupts bacterial membranes but also compromises their metabolic function, making it a robust antimicrobial strategy.

Comparison of Olive Pomace Extract with Conventional Sanitizers

Conventional sanitizers, such as chlorine-based compounds, are widely used in the food industry; however, they often lead to the formation of toxic disinfection byproducts and are less effective against biofilms. The antimicrobial efficacy of OPE combined with UV-A light was assessed against traditional sanitizers like sodium hypochlorite.

The findings suggest that OPE combined with UV-A light not only provides a more sustainable and environmentally friendly alternative but also demonstrates greater efficacy against bacterial pathogens and their biofilms compared to conventional sanitizers.

Impact of Phenolic Components on Antimicrobial Activities

The phenolic components in OPE contribute significantly to its antimicrobial properties. The major phenolic compounds identified—4-hydroxyphenylacetic acid, hydroxytyrosol, and gallic acid—exhibit distinct antimicrobial activities. The study assessed their individual effects in combination with UV-A light, revealing varying degrees of synergism:

The results indicate that 4-hydroxyphenylacetic acid and hydroxytyrosol exhibited the strongest synergistic effects with UV-A light, suggesting their critical role in enhancing the antimicrobial efficacy of OPE. This underscores the importance of leveraging the diverse phenolic components in OPE to achieve optimal antimicrobial activity.

Evaluating Antibiofilm Properties of Olive Pomace Extract and UV-A Light

The efficacy of OPE combined with UV-A light against established bacterial biofilms was also evaluated. The treatment demonstrated significant reductions in biofilm density, achieving over 6-log reductions for both E. coli O157:H7 and L. innocua within 60 minutes of treatment.

The results reinforce the potential of using OPE as a natural antimicrobial agent that not only targets planktonic cells but also effectively disrupts biofilms, which are notoriously difficult to eradicate with traditional sanitizers.

Conclusion

The findings of this study highlight the strong synergistic potential of olive pomace extract combined with UV-A light as an effective antimicrobial strategy against bacterial pathogens and their biofilms. The mechanisms involving oxidative stress induction, membrane damage, and metabolic inhibition underscore the multifaceted approach of this treatment. This innovative application provides a sustainable alternative to conventional sanitizers, leveraging agricultural byproducts to enhance food safety.

FAQ

What is olive pomace extract?
Olive pomace extract is derived from the byproducts of olive oil production, particularly the solid remains after the oil has been extracted. It is rich in phenolic compounds known for their antioxidant and antimicrobial properties.

How does UV-A light enhance the antimicrobial activity of olive pomace extract?
UV-A light can activate the phenolic compounds in olive pomace extract, leading to the generation of reactive oxygen species (ROS) that cause oxidative stress and damage bacterial membranes, enhancing the overall antimicrobial effect.

Is the combination of olive pomace extract and UV-A light safe for food applications?
Yes, both olive pomace extract and UV-A light are considered safe for food applications. OPE is derived from a natural source and UV-A light is a non-thermal treatment that does not leave harmful residues.

What types of bacteria were tested in the study?
The study primarily tested Escherichia coli O157:H7 and Listeria innocua, which are common foodborne pathogens.

Can this treatment replace conventional sanitizers in the food industry?
The study suggests that the combination of olive pomace extract and UV-A light can serve as a promising alternative to conventional sanitizers, especially for their effectiveness against biofilms and lower environmental impact.

References

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