Using Protein Hydrolysates as Biostimulants
Protein hydrolysates are an important group of plant biostimulants that have received increasing attention in recent years due to their positive effect on crop performance and more particularly under environmental stress conditions[1].
Description
Proteins are macromolecules present in all living cells. They are mainly composed of Carbon, Hydrogen, Oxygen, and Nitrogen. They perform a multitude of biological functions (gene regulation, cell structure, catalyst of biological processes (enzymes)…) and are composed of peptides, themselves made up of amino acids.
The biostimulant action of peptides
Research has shown various biostimulant effects of protein hydrolysates:
- Beneficial effects of hydrolyzed soybean cakes by Bacillus circulans HA12 proteases on the growth of crops[2].
- Significant growth of root and leaf biomass of maize induced by an alfalfa hydrolysate[3].
- "Auxin-like" and "gibberellin-like" effects induced by an enzymatic hydrolysate of legume plant proteins[4].
- Increased plant resistance to salt stress and drought.
- Stimulation of photosynthesis.
- Increase in amino acid production.
- Improvement of germination, quality, and productivity of crops.
- Stimulation of carbon and nitrogen metabolism and interference with plant hormonal activity.
- Improvement of availability of nutrients in the growing substrate and increased nutrient uptake and nutrient use efficiency by plants.
- Stimulation of the plant microbiome[5].
The biostimulant effects of protein hydrolysates vary depending on:
- The crops on which they are applied.
- Their composition, which itself depends on the raw material and the hydrolysis process used and the Degree of Hydrolysis.
The biostimulant action of amino acids
Amino acids play a very important role in the plant as they are involved in all metabolisms, in the constitution of plant proteins, and in the synthesis of vitamins.
Some amino acids have specific reactive processes allowing them to meet precise objectives:
| Function | Acid amino acid |
| Nutrient assimilation | Aspartate |
| Alanine | |
| Asparagine | |
| Glutamine | |
| Energy production | Leucine |
| Isoleucine | |
| Cystine | |
| Valine | |
| Stress signaling | Proline |
| Glutamate | |
| Serine |
Table 1: Effects of certain amino acids on plants[6]
The biostimulant action of amino acids thus depends on each plant and its developmental stage.
Raw materials and hydrolysis processes
Protein hydrolysates are mainly produced by enzymatic or chemical hydrolysis of animal or plant proteins[7].
More than 90% of the protein hydrolysate market in agriculture is based on products obtained by chemical hydrolysis of animal-origin proteins while protein hydrolysates obtained by enzymatic hydrolysis of biomass from plants (seeds, plant by-products…) are less common because they have appeared more recently on the biostimulant market.
Whatever the hydrolysis technique used and the origin of the raw material, the parameter that most conditions the properties of protein hydrolysates is the Degree of Hydrolysis (DH). While strong chemical hydrolysis (DH ≥ 40%) leads to a high rate of free amino acids, moderate enzymatic hydrolysis (DH ≤ 30%) results in a low rate of free amino acids and peptide fragments of large size (1 – 20 kDa).
In the first case (DH ≥ 40%), the protein hydrolysate will have fertilizing properties and effects specific to the free amino acids it contains. In the second case, the properties of the protein hydrolysate will be mainly related to the original proteins of the product and the peptides derived from them[1].
Advantages
The main advantage of protein hydrolysates is that they positively stimulate all processes of primary and secondary plant metabolisms, such as:
- Photosynthesis
- DNA and protein synthesis,
- Stress resistance,
- Fruit ripening,
- Nutrient uptake.
These biostimulants also create a favorable environment for plant growth and crop quality by:
- Stimulating soil microflora.
- Promoting a higher content of antioxidants and proteins and a lower nitrate content in the final product[8].
Regulation
European Regulation 354/20144 (amended by Regulation 2018/1584) authorizes the use of plant-origin protein hydrolysates in Organic Agriculture. However, the use of hydrolyzed animal-origin proteins is not authorized on the edible parts of plants.
La technique est complémentaire des techniques suivantes
- ↑ 1.0 1.1 Académie des biostimulants, online, ORGANIC BIOSTIMULANTS: The example of protein hydrolysates
- ↑ Kubo M, Okajima J, Hasumi F, 1994, Isolation and Characterization of Soybean Waste-Degrading Microorganisms and Analysis of Fertilizer Effects of the Degraded Products, Appl. Environ. Microbiol, 60(1), 243-247
- ↑ Ertani A, Cavani L, Pizzeghello D, Brandellero E, Altissimo A, Ciavatta C, Nardi S, 2009, Biostimulant activity of two protein hydrolyzates in the growth and nitrogen metabolism of maize seedlings, J. Plant Nutr. Soil Sci., 172: 237–244
- ↑ Colla G, Rouphael Y, Lucini L, Canaguier R, Stefanoni W, Fiorillo A, Cardarelli M, 2016, Protein hydrolysate-based biostimulants: origin, biological activity and application methods, Acta Hortic., ISHS, 1148: 27-34
- ↑ Colla G, Hoagland L, Ruzzi M, Cardarelli M, Bonini P, Canaguier R and Rouphael Y (2017) Biostimulant Action of Protein Hydrolysates: Unraveling Their Effects on Plant Physiology and Microbiome. Front. Plant Sci. 8:2202. doi: 10.3389/fpls.2017.02202
- ↑ Heller, Esnault and Lance, 2004 Plant Physiology 1. Nutrition, 6th edition
- ↑ Colla, G., Nardi, S., Cardarelli, M., Ertani, A., Lucini, L., Canaguier, R., et al. (2015). Protein hydrolysates as biostimulants in horticulture. Sci. Hortic. 96, 28–38. doi: 10.1016/j.scienta.2015.08.037
- ↑ BlueBerries Consulting, online, https://blueberriesconsulting.com/fr/utilizar-bioestimulantes-cultivo-los-arandanos/
