Characterization of humic acids derived from Leonardite using a solid-state NMR spectroscopy and effects of humic acids on growth and nutrient uptake of snap bean

A practical guide to the discovery of biomolecules with biostimulant activity

The growing demand for sustainable solutions in agriculture, which are critical for crop productivity and food quality in the face of climate change and the need to reduce agrochemical usage, has brought biostimulants into the spotlight as valuable tools for regenerative agriculture. With their diverse biological activities, biostimulants can contribute to crop growth, nutrient use efficiency, and abiotic stress resilience, as well as to the restoration of soil health. Biomolecules include humic substances, protein lysates, phenolics, and carbohydrates have undergone thorough investigation because of their demonstrated biostimulant activities. Here, we review the process of the discovery and development of extract-based biostimulants, and propose a practical step-by-step pipeline that starts with initial identification of biomolecules, followed by extraction and isolation, determination of bioactivity, identification of active compound(s), elucidation of mechanisms, formulation, and assessment of effectiveness. The different steps generate a roadmap that aims to expedite the transfer of interdisciplinary knowledge from laboratory-scale studies to pilot-scale production in practical scenarios that are aligned with the prevailing regulatory frameworks.

Efficient adsorption and photocatalytic degradation of water emerging contaminants through nanoarchitectonics of pore sizes and optical properties of zirconium-based MOFs

Over the past decades, the presence of pharmaceutical emerging contaminants in water bodies is receiving increasing attention due to the high concentration detected from wastewater effluent. Water systems contain a wide range of components coexisting together, which increases the difficulty of removing pollutants from the water. In order to achieve selective photodegradation and to enhance the photocatalytic activity of the photocatalyst on emerging contaminants, a Zr-based metal-organic framework (MOF), termed VNU-1 (VNU represents Vietnam National University) constructed with ditopic linker 1,4-bis(2-[4-carboxyphenyl]ethynyl)benzene (H₂CPEB), with enlarged pore size and ameliorated optical properties, was synthesized and applied in this study. When compared to UiO-66 MOFs, which only had 30% photodegradation of sulfamethoxazole, VNU-1 had 7.5 times higher adsorption and reached 100% photodegradation in 10 min. The tailored pore size of VNU-1 resulted in size-selective properties between small-molecule antibiotics and big-molecule humic acid, and VNU-1 maintained high photodegradation performance after 5 cycles. Based on the toxicity test and the scavenger test, the products after photodegradation had no toxic effect on V. fischeri bacteria, and the superoxide radical (·O₂^-) and holes (h⁺) generated from VNU-1 dominated the photodegradation reaction. These results demonstrate that VNU-1 is a promising photocatalyst and provide a new insight for developing MOF photocatalyst to remove emerging contaminants in the wastewater systems.

Exploration of the H2O2 Oxidation Process and Characteristic Evaluation of Humic Acids from Two Typical Lignites

To study the effect of H2O2 on the content and properties of humic acids (HAs) in lignites, the experimental conditions including oxidation time, H2O2 concentration, and the solid-liquid ratio were investigated. Under the optimum oxidation conditions, the contents of HAs of YL and HB lignite were 45.4 and 40.9%, respectively. The HAs extracted from oxidized and raw lignites were characterized and compared. The results showed that the HAs extracted from oxidized lignites contain more total acidic groups, carboxyl groups, and aliphatic carbon than that in HAs extracted from raw lignites, and their hydrophilic-hydrophobic index value is higher and thermooxidative stability is better than those in HAs extracted from raw lignites. In addition, the composition of polycyclic aromatic hydrocarbons and fluorophore types in HAs extracted from oxidized lignites are similar to the HAs extracted from raw lignites. The results indicated that the oxidation operation can increase the content of HAs in lignites, and simultaneously increase the content of oxygen-containing functional groups and biological activity of HAs, which provided a reference for the subsequent application of HAs.

Effect of Humic Substances as Feed Additive on the Growth Performance, Antioxidant Status, and Health Condition of African Catfish (Clarias gariepinus, Burchell 1822)

Simple Summary

Global aquaculture requires the development of new strategies to maintain the continuous growth of production, such as the development of aquafeeds with sustainable and functional components, ensuring better growth and health conditions of fish. Humic substances (HS) have the potential to become a functional additive for aquafeeds, as their growth-promoting and immunostimulant effects have been found in farm animals. Recently, there is limited knowledge on how different HS affects overall performance of various fish species. Therefore, in this study, the effects of four experimental Siberian leonardite HS diets (HS0, HS1, HS3, and HS6) on growth and production parameters, condition and somatic indices, overall mortality, health condition, and antioxidant status were assessed in juvenile Clarias gariepinus, which is well-known as a fast-growing and high-resistant fish species when reared at high stocking densities up to 500 kg m⁻³. In this study, growth and production parameters, condition, and somatic indices or mortality rate were not significantly affected by tested HS diets. On the other hand, moderately positive effects were observed regarding health status and good antioxidant parameters, especially in the HS3 group over the 56-day study.

Abstract

In the present study, a possible nature immunostimulant and growth promoter—humic substances (HS) originating from Siberian leonardite mineraloid—were tested on juvenile Clarias gariepinus performance. Feed additive was applied onto commercial pelleted feed at four HS levels—0, 1, 3, and 6% w/w (HS0, HS1, HS3, HS6, respectively). Diets were tested in five repetitions (in total, n = 1800 individuals, mean body weight 28.1 ± 6.2 g) for 56 days. Growth and production parameters, fish condition and somatic indices, and overall mortality were evaluated after 14, 28, 42, and 56 days of exposure. Whereas, plasma samples were collected only after 0, 28, and 56 days, when fish health status was assessed with biochemical parameters (total proteins, TP; alanine aminotransferase, ALT; aspartate aminotransferase, AST; lactate dehydrogenase, LDH; cholesterol, CHOL; triglycerides, TAG) and fish antioxidant status with glutathione (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione ratio GSH/GSSG). Although a significantly positive effect of HS feed additive on growth performance was not found in the present study, moderately positive effects were found regarding biochemical parameters (ALT, AST, LDH, CHOL, and TAG) and antioxidants (GSH/GSSG ratio) that were improved especially in the HS3 group.

Sorption of Organic Pollutants by Humic Acids: A Review

Humic acids (HA) are promising green materials for water and wastewater treatment. They show a strong ability to sorb cationic and hydrophobic organic pollutants. Cationic compounds interact mainly by electrostatic interaction with the deprotonated carboxylic groups of HA. Other functional groups of HA such as quinones, may form covalent bonds with aromatic ammines or similar organic compounds. Computational and experimental works show that the interaction of HA with hydrophobic organics is mainly due to π-π interactions, hydrophobic effect and hydrogen bonding. Several works report that sorbing efficiency is related to the hydrophobicity of the sorbate. Papers about the interaction between organic pollutants and humic acids dissolved in solution, in the solid state and adsorbed onto solid particles, like aluminosilicates and magnetic materials, are reviewed and discussed. A short discussion of the thermodynamics and kinetics of the sorption process, with indication of the main mistakes reported in literature, is also given.