Abstract
Crop production systems have adopted cost-effective, sustainable and environmentally friendly agricultural practices to improve crop yields and the quality of food derived from plants. Approaches such as genetic selection and the creation of varieties displaying favorable traits such as disease and drought resistance have been used in the past and continue to be used. However, the use of biostimulants to promote plant growth has increasingly gained attention, and the market size for biostimulants is estimated to reach USD 4.14 billion by 2025. Plant biostimulants are products obtained from different inorganic or organic substances and microorganisms that can improve plant growth and productivity and abate the negative effects of abiotic stresses. They include materials such as protein hydrolysates, amino acids, humic substances, seaweed extracts and food or industrial waste-derived compounds. Fish processing waste products have potential applications as plant biostimulants. This review gives an overview of plant biostimulants with a focus on fish protein hydrolysates and legislation governing the use of plant biostimulants in agriculture.
Highlights
To reduce the number of toxic nitrates in the soil, the EU Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources (91/676/EEC) called for a significant reduction in the amount of nitrogen-containing fertilizers used in agriculture and horticulture
According to the free amino acid composition, the results indicated the potential use of the hydrolysate as a supplement for use in animal diets [44]
In order to maintain and ensure consistence in biostimulant product quality, many methods are used to qualitatively and quantitively analyze the compounds present in commercial biostimulants products [10]. These methods include amino acid analysis, bioassays, ecotoxicological tests, Fourier transform infrared spectroscopy (FTIR), gas chromatography coupled with mass spectrometry (GC/MS), sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE), 13C NMR, 1H NMR, atmospheric pressure chemical ionization-mass spectrometry (APCI-MS), cross-polarization magic angle spinning (CP/MAS), (CPMAS)-13C-NMR, diffuse-reflectance infrared Fourier transform spectroscopy (DRIFT), electronic microscopy, elemental analysis, high performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS), pyrolysis-gas chromatography-mass spectrometry, UV–vis and ELISA [107]
Summary
To reduce the number of toxic nitrates in the soil, the EU Council Directive of 12 December 1991 concerning the protection of waters against pollution caused by nitrates from agricultural sources (91/676/EEC) called for a significant reduction in the amount of nitrogen-containing fertilizers used in agriculture and horticulture. Biostimulants are products able to act on the metabolic and enzymatic processes of plants improving productivity and crop quality. Animal sources of biostimulants are usually hydrolysates of food by-products such as casein [4], fish waste [5]. Plant biostimulants can be grouped on the basis of their origin, for example, humic substances (humic acids, fulvic acids, and humins), seaweed extracts, protein hydrolysates (plant and animal origin), beneficial microorganisms (bacteria and fungi), chitosans, silicon, and extracts from food waste or industrial waste streams among others [9]. Animal processing by-products are ordinarily converted into protein hydrolysates using chemical or enzymatic hydrolysis for use as biostimulants. Methods of identification of biostimulants generated from fish and animal by-products include amino acid analysis, eco-toxicological tests and sodium dodecyl sulphate polyacrylamide gel electrophoresis.
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