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Background <p>The valorization of agro-industrial by-products is a key strategy for promoting sustainable agriculture and minimizing environmental impacts. Olive mill wastewater (OMW) and olive leaves (OL) contain high concentrations of phenolic compounds, which have shown potential as biological nitrification inhibitors (BNIs), offering a sustainable alternative to reduce nitrogen pollution in agroecosystems. This study aims to characterize the phenolic profile of these by-products, assess their antioxidant properties, evaluate their inhibitory effects on nitrification, and determine their biodegradability.</p> Results <p>Hydroxytyrosol (1.521&#xa0;g&#xa0;L⁻<sup>1</sup>) was identified as the dominant phenolic compound in OMW, while oleuropein (1.824&#xa0;g&#xa0;L⁻<sup>1</sup>) prevailed in OL extracts. Both solutions exhibited moderate to high antioxidant activity, with DPPH EC50 values of 1.84 and 2.06&#xa0;mg&#xa0;L⁻<sup>1</sup> for OL and OMW, respectively. Nitrification inhibition assays using <i>Nitrosomonas europaea</i> showed IC50 values of 0.2806&#xa0;g&#xa0;L⁻<sup>1</sup> for OMW and 0.1735&#xa0;g&#xa0;L⁻<sup>1</sup> for OL. Biodegradability tests indicated degradation rates of 52–53% for OMW and 54–55% for OL at 350 and 700&#xa0;mg&#xa0;L⁻<sup>1</sup> COD. Elemental analysis confirmed the presence of essential macronutrients (K, P, Ca, Mg) and micronutrients (Fe, Zn, Mn, Cu, Ni) in both solutions, supporting soil fertility while maintaining low heavy metal concentrations.</p> Conclusions <p>These findings highlight the dual benefits of OMW and OL solutions: reducing nitrogen losses through nitrification inhibition while contributing to soil health and circular economy models. Although their biodegradability does not strictly meet OECD criteria for readily biodegradable compounds, optimizing microbial communities could enhance their degradation. The application of these biological nitrification inhibitors presents a promising alternative to synthetic nitrification inhibitors, fostering eco-friendly agricultural practices.</p> Graphical Abstract <p></p>

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Valorizing olive oil by-products as sustainable biological nitrification inhibitors: phenolic profiling, in vitro activity against Nitrosomonas europaea, and biodegradability assessment

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月12日

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  • Adrián Hernández Fernández,
  • Eduardo Iniesta Lopez,
  • Yolanda Garrido,
  • Ana Sánchez Zurano,
  • Antonia Pérez de los Ríos,
  • Francisco José Hernández Fernández

摘要

Background

The valorization of agro-industrial by-products is a key strategy for promoting sustainable agriculture and minimizing environmental impacts. Olive mill wastewater (OMW) and olive leaves (OL) contain high concentrations of phenolic compounds, which have shown potential as biological nitrification inhibitors (BNIs), offering a sustainable alternative to reduce nitrogen pollution in agroecosystems. This study aims to characterize the phenolic profile of these by-products, assess their antioxidant properties, evaluate their inhibitory effects on nitrification, and determine their biodegradability.

Results

Hydroxytyrosol (1.521 g L⁻1) was identified as the dominant phenolic compound in OMW, while oleuropein (1.824 g L⁻1) prevailed in OL extracts. Both solutions exhibited moderate to high antioxidant activity, with DPPH EC50 values of 1.84 and 2.06 mg L⁻1 for OL and OMW, respectively. Nitrification inhibition assays using Nitrosomonas europaea showed IC50 values of 0.2806 g L⁻1 for OMW and 0.1735 g L⁻1 for OL. Biodegradability tests indicated degradation rates of 52–53% for OMW and 54–55% for OL at 350 and 700 mg L⁻1 COD. Elemental analysis confirmed the presence of essential macronutrients (K, P, Ca, Mg) and micronutrients (Fe, Zn, Mn, Cu, Ni) in both solutions, supporting soil fertility while maintaining low heavy metal concentrations.

Conclusions

These findings highlight the dual benefits of OMW and OL solutions: reducing nitrogen losses through nitrification inhibition while contributing to soil health and circular economy models. Although their biodegradability does not strictly meet OECD criteria for readily biodegradable compounds, optimizing microbial communities could enhance their degradation. The application of these biological nitrification inhibitors presents a promising alternative to synthetic nitrification inhibitors, fostering eco-friendly agricultural practices.

Graphical Abstract