Alginic Acid and Algal Oligosaccharides

Abstract: Alginic acid is a natural polysaccharide polymer that widely exists in brown algae and is widely distributed in nature. Algal oligosaccharide is a small molecular fragment obtained by the degradation of alginic acid, which has the effect of regulating plant growth and improving plant disease resistance. Seaweed extract is a typical product rich in seaweed extracts such as alginic acid and seaweed oligosaccharides. Seaweed fertilizers have the incomparable advantages of chemical fertilizers, such as increasing production, stress resistance, and no toxic side effects. 

1. Alginic Acid

Alginic acid is the hallmark ingredient in seaweed fertilizers. Alginic acid widely exists in brown algae cell wall and intercellular substance. It is a polysaccharide formed by linear polymerization of monouronic acid. It is the main energy supply material of plants and plays a role in strengthening the cell wall. The molecular formula of alginic acid is C6H8O6, and the molecular weight ranges from 10,000 to 600,000. Due to the different origins and climatic environments, different species of brown algae have their unique structures and biological properties, and the alginic acids extracted from different brown algae also have different chemical structures and physical properties. Alginic acid can reduce the surface tension of water, increase the contact area between the medicinal liquid and the leaf surface, and has stronger water retention, making it easier for water-soluble substances to enter crop cells through the cell membrane on the surface of stems and leaves, so that crops can more effectively absorb the nutrient content in seaweed extract. At the same time, the carboxyl groups and hydroxyl groups in the alginic acid molecule are easily combined with the metal ions in the soil to form a cross-linked polymer with a doubled molecular weight. This polymer salt can be firmly combined with water molecules to promote the soil to form a granular structure and retain water. 

2. Algal Oligosaccharides

Algal oligosaccharides are small molecular weight fragments obtained from alginic acid degradation by acid, oxidant or lyase. Algal oligosaccharides have good water solubility and are easy to be absorbed and utilized. Algal oligosaccharides can play an active role in plant growth regulation and inducing disease resistance. It has high elicitor activity and can induce plants to produce phytochemicals and defense response factors in the physiological process of plant disease resistance, to resist the infection of foreign microorganisms, or directly act on pathogenic bacteria to participate in the anti-induction process of plants. Algal oligosaccharide is also an important signal molecule for plants, which can promote the growth of plants. A certain concentration of algal oligosaccharide can promote the absorption of nitrogen, phosphorus and many mineral elements by crops. This provides favorable conditions for its use as a nitrogen fertilizer synergist.