Controlled release system for astaxanthin biofertilizer and stress resistance

Abstract

A controlled release device for improved plant growth and increased stress resistance, comprising an active ingredient encapsulated in a biodegradable hydrogel matrix, wherein the active ingredient is astaxanthin, which reduces oxidative stress, and wherein the hydrogel matrix controls the release of the astaxanthin over a longer period of time.

Description

Application area of ​​the invention

[0001] The present invention relates to a controlled-release biofertilizer system that utilizes a biodegradable hydrogel to increase crop yield and improve the resistance of plants to environmental stress. Background of the invention

[0002] Modern agriculture faces major challenges, primarily increasing crop yields while simultaneously reducing environmental impact and the use of synthetic chemicals. Abiotic stress, such as drought, extreme temperatures, or high light intensity, severely limits plant productivity by triggering oxidative stress through the excessive production of reactive oxygen species (ROS) in plant tissue (Bao et al., 2017). While plants can cope with this stress naturally, current cultivation methods often exceed their natural capacity. There is an urgent need for sustainable inputs that effectively protect plants while simultaneously providing them with nutrients. Conventional fertilizers, whether liquid or solid, often exhibit low nutrient efficiency and leaching, leading to environmental pollution and resource waste.Astaxanthin, a potent keto-carotenoid from microalgae, offers a promising solution due to its superior antioxidant activity. It can effectively neutralize ROS and promote photosynthesis (Guedes et al., 2011). However, for effective application, a protective, slow-release mechanism is required to ensure sustained bioactivity and uptake throughout the plant's growth cycle. Summary of the invention

[0003] The present invention relates to a novel system for the controlled release of astaxanthin biofertilizer. This system is designed as a composite device, typically in the form of macroporous granules or injectable microcapsules, wherein a biofertilizer core composition is embedded in a biodegradable hydrogel matrix. The main function of this system is to serve as a reservoir for delayed release, delivering astaxanthin and essential nutrients directly into the rhizosphere over an extended period. This developed device fundamentally solves the problem of the short-term application and rapid degradation of bioactive compounds, thereby maximizing the bioprotective effect of astaxanthin against environmental stressors.

[0004] The device ensures that the encapsulated astaxanthin, often derived from Haematococcus, is released gradually by *Pluvialis*, thus enabling a sustained reduction in oxidative stress in the plants. This leads to improved root development and increased photosynthetic performance. The integration of the protective hydrogel shell significantly improves nutrient utilization efficiency, reducing the need for fertilizer and the overall amount of synthetic fertilizer. The system design promotes sustainable farming practices by improving soil health and providing plants with a stable protective mechanism. This results in significantly higher yields and increased drought tolerance. Detailed description

[0005] The present invention relates to a controlled-release device specifically designed for the sustained, localized, and environmentally dependent release of an astaxanthin-based biofertilizer formulation. In its preferred embodiment, the device is a granulated polymer component comprising three primary functional components: a highly effective astaxanthin core, a matrix of essential macro- and micronutrients, and an outer hydrogel shell.

[0006] The astaxanthin component is crucial because it acts as a primary stress reducer. It is derived from the microalga Haematococcus. Astaxanthin is obtained either through natural synthesis or via a reliable biotechnological process, ensuring high purity. Once released by the system, astaxanthin acts as a potent antioxidant, scavenging reactive oxygen species (ROS) that accumulate under abiotic stress conditions such as dehydration, heat, or salinity. This protects cellular mechanisms and enhances the overall vitality of the plant (Vundavalli et al., 2021).

[0007] The hydrogel encapsulation shell serves as the structural and rate-limiting element of the device. This shell consists of hydrophilic, biodegradable polymers such as chitosan, alginate, or polyacrylamide, which were selected for their high water retention capacity and precisely adjustable degradation rate. Upon contact with soil moisture, the hydrogel swells, forming a protective, three-dimensional porous network that controls the diffusion rate of the active ingredients (Vundavalli et al., 2021).

[0008] Within this hydrogel shell is the nutrient matrix, which consists of standard NPK fertilizers (nitrogen, phosphorus, potassium) and is enriched with essential micronutrients such as iron, zinc, and manganese. This matrix is ​​designed to ensure a balanced and comprehensive supply of nutrients, working synergistically with the astaxanthin to support robust plant growth and recovery from stress.

[0009] The physical form of the device is preferably a spherical or irregular granular pellet, the size of which is optimally suited for conventional mechanical application or direct application into the planting hole. This form ensures minimal dust generation, easy handling, and precise application rates, thus distinguishing it from conventional powder or liquid fertilizers.

[0010] The release mechanism is determined by the hydrogel's response to environmental conditions in the soil. As the hydrogel slowly degrades and swells, nutrients and astaxanthin are released primarily via two mechanisms: diffusion through the swollen polymer network and gradual polymer degradation. This design allows for the consistent release of active ingredients over several months, thus covering the entire growing season of most crops.

[0011] The application of this device in the field has demonstrated significant effectiveness. The continuous release of astaxanthin directly mitigates stress, increases photosynthetic performance, and enhances root biomass (Bao et al., 2017). This biological protection leads to significantly higher crop yields and substantially improved drought tolerance, with plants exhibiting a higher relative water content.

[0012] The system also contributes to ecological sustainability by significantly reducing nutrient leaching. The slow release of nutrients through the hydrogel minimizes the immediate loss of soluble nutrients, thus preventing their runoff and increasing the plant's nutrient utilization efficiency (NUE). This, in turn, allows for a reduction in the overall amount of synthetic fertilizer required.

[0013] In summary, the Controlled Delivery System functions as a highly efficient agricultural input device that integrates bioprotection and nutrient supply in a single, specially developed and biodegradable polymer shell, thus setting a new standard for sustainable crop management. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Vundavalli et al., 2021 [0006, 0007] Bao et al., 2017

[0011]

Claims

[1] A controlled release device for improved plant growth and increased stress resistance, comprising an active ingredient encapsulated in a biodegradable hydrogel matrix, wherein the active ingredient is astaxanthin, which reduces oxidative stress, and wherein the hydrogel matrix controls the release of the astaxanthin over a longer period of time. [2] Device according to claim 1, wherein the astaxanthin is obtained from the microalga Haematococcus pluvialis and improves photosynthesis efficiency and root development by reducing reactive oxygen species in plant tissue. [3] Device according to claim 1, wherein the biodegradable hydrogel matrix further comprises a delayed release macro- and micronutrient formulation, has high water retention and is structured as an integrated granule pellet for mechanical application. [4] Device according to claim 3, wherein the device is configured to significantly improve the drought tolerance of the plant and increase the overall crop yield due to the synergistic and prolonged release of astaxanthin and the balanced nutrient formulation.