Abstract
A novel strategy involving Olive Leaf Extract (OLE) and Cold Atmospheric Plasma (CAP) was developed as a green antimicrobial treatment. Specifically, we reported a preliminary investigation on the combined use of OLE + CAP against three pathogens, chosen to represent medical and food industries (i.e., E. coli, S. aureus and L. innocua). The results indicated that a concentration of 100 mg/mL (total polyphenols) in OLE can exert an antimicrobial activity, but still insufficient for a total bacterial inactivation. By using plain OLE, we significantly reduced the growth of Gram positive S. aureus and L. innocua, but not Gram-negative E. coli. Instead, we demonstrated a remarkable decontamination effect of OLE + CAP in E. coli, S. aureus and L. innocua samples after 6 h. This effect was optimally maintained up to 24 h in S. aureus strain. E. coli and L. innocua grew again in 24 h. In the latter strain, OLE alone was most effective to significantly reduce bacterial growth. By further adjusting the parameters of OLE + CAP technology, e.g., OLE amount and CAP exposure, it could be possible to prolong the initial powerful decontamination over a longer time. Since OLE derives from a bio-waste and CAP is a non-thermal technology based on ionized air, we propose OLE + CAP as a potential green platform for bacterial decontamination. As a combination, OLE and CAP can lead to better antimicrobial activity than individually and may replace or complement conventional thermal procedures in food and biomedical industries.
Highlights
Some molecules and plant-derivatives demonstrate good antimicrobial activity against pathogenic bacteria found in packaging or processing phases in the food industry [1], as well as in biomedical devices, such as surgical tools and supporting equipment, the latter being very important in healthcare, since inaccurate sterilization is responsible for at least 1.5%–7.2% of post-operative complications [2]
Olive Leaf Extract (OLE) + Cold Atmospheric Plasma (CAP) treatment was sufficiently effective on E. coli, which grew by reaching ~7∙Log was stilland remarkably on S.effective aureus, which up which to ~3·Log was stilleffective remarkably on S.grew aureus, grew up tothus
Since OLE derives from a bio-waste and CAP is a non-thermal technology based on ionized air, we propose OLE + CAP as a novel green approach potentially useful for bacterial decontamination
Summary
Another emerging non-thermal technology with potential applications in several different industries, including safe and sustainable food production, is Cold Atmospheric. Fabrics were previously pre-treated by an argon/oxygen (Ar/O2 ) dielectric barrier discharge (DBD) plasma for surface activation, subsequently exposed to the atmosphere for further oxidization and, immersed in a chitosan solution for chitosan grafting. Other natural compounds, such as nisin peptides, thymol and herbs, have been grafted onto plasma pre-treated polymer surfaces to obtain an antibacterial material [38,39,40].
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