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Antimicrobial and Antifungal Activities of Proline-Based 2,5-Diketopiperazines Occurring in Food and Beverages and Their Synergism with Lactic Acid

Summary

Researchers synthesized special cyclic peptides called 2,5-diketopiperazines (found naturally in fermented foods like bread and cheese) and tested their ability to kill harmful molds and bacteria. When combined with lactic acid (a natural preservative), these compounds worked extremely well together, achieving nearly complete mold inhibition. This research suggests that using special starter cultures that naturally produce these compounds could help keep food fresh longer without artificial preservatives.

Background

2,5-Diketopiperazines (2,5-DKPs), particularly proline-based variants (Pro-DKPs), are naturally occurring cyclic peptides found in fermented foods and beverages. While their antimicrobial properties have been noted, their synergistic effects with other secondary metabolites in real food matrices remain largely unexplored. This study synthesized and evaluated major food-derived Pro-DKPs for antimicrobial efficacy.

Objective

To synthesize proline-based 2,5-diketopiperazines and evaluate their antimicrobial and antifungal activities against common foodborne pathogens at food-relevant concentrations. The study also investigated the synergistic effects of Pro-DKPs combined with lactic acid and assessed their antifungal properties in a real food matrix (bread).

Results

Among synthesized Pro-DKPs, cyclo(l-Leu-l-Pro) inhibited DMF 0109 growth by up to 83% in poisoned plate assays. When combined with lactic acid, all three Pro-DKPs demonstrated enhanced antimicrobial activity, with inhibitions reaching 99% against DMF 0109. Selected LAB and mold strains produced Pro-DKPs naturally in fermentation broths, with strain-specific production patterns observed.

Conclusion

Proline-based 2,5-diketopiperazines exhibit significant antifungal activity, which is substantially enhanced by combination with lactic acid. The findings suggest that commercial starter cultures capable of producing Pro-DKPs may offer a promising strategy for extending shelf life of food products and beverages through synergistic antimicrobial effects.
  • Published in:ACS Agricultural Science & Technology,
  • Study Type:Experimental Study,
  • Source: PMC12365876, PMID: 40842631, DOI: 10.1021/acsagscitech.5c00236
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