Antibacterial and antioxidant properties of humic substances from composted agricultural biomasses

Mariavittoria Verrillo, Melania Salzano, Davide Savy*, Vincenzo Di Meo, Massimiliano Valentini, Vincenza Cozzolino, Alessandro Piccolo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Background: Bioactive components isolated from composted agricultural biomasses have been receiving progressive attention, because they may improve the antibiotic susceptibility of drug resistant bacterial strains. Here, three different humic substances (HS) were isolated from composted artichoke (HS-CYN) and pepper (HS-PEP) wastes, and from coffee grounds (HS-COF), and characterized by infrared spectrometry, NMR spectroscopy, thermochemolysis–GC/MS, and high-performance size-exclusion chromatography. The antibacterial activity of HS was evaluated against some pathogenic bacterial strains, while their bioactivity was determined by a germination assay on basil (Red–Violet variety) seeds. Results: HS-CYN and HS-PEP exhibited the largest antioxidant activity and most significant antimicrobial capacity against some gram-positive bacterial strains, such as Staphylococcus aureus and Enterococcus faecalis. The same HS determined a significant increase of both root and epicotyls in seed germination experiments. The bioactivity of HS was related not only to their specific molecular composition but also to the conformational stability of their suprastructures. Specifically, the greatest bioactive and antimicrobial properties were related to the largest abundance of hydrophobic aromatic and phenolic components and to a more rigid conformational arrangement, that, in turn, appeared to be related to a small fragmentation degree of lignin structures. Conclusions: Our results showed that extraction of bioactive HS from green composts may be a sustainable and eco-compatible way to valorise agricultural byproducts. HS may be indeed exploited as substrates to produce novel materials not only to improve plant productivity but also for medical applications. Graphical Abstract: [Figure not available: see fulltext.]

Original languageEnglish
Article number28
JournalChemical and Biological Technologies in Agriculture
Volume9
Issue number1
DOIs
Publication statusPublished - Dec 2022

Keywords

  • C-CPMAS NMR
  • Diffusion disk
  • Green compost Seed germination
  • High-Performance Size-Exclusion Chromatography (HPSEC)
  • Humic substances
  • Minimal inhibitory concentration
  • Radical scavenging capacity
  • Structure–activity relationship
  • Thermochemolysis

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Biochemistry
  • Agronomy and Crop Science

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