Alginate is a polysaccharide with the property of forming hydrogels, which is economic production, zero toxicity, and biocompatibility. In the agro-industry, alginate is used as a super absorbent polymer, coating seeds, fruits, and vegetables and as a carrier of bacteria and fungi as plant-growth promoters and biocontrol. The latter has a high impact on agriculture since the implementation of microorganisms in a polymer matrix improves soil quality; plant nutrition, and is functional as a preventive measure for the appearance of phytopathogenic. Additionally, it minimizes losses of foods due to wrong post-harvest handling. In this review, we provide an overview of physicochemical properties of alginate, some methods for preparation and modification of capsules and coatings, to finally describe its application in agro-industry as a matrix of plant-growth-promoting microorganisms, its effectiveness in cultivation and post-harvest, and its effect on the environment, as well as the prospects for future agro-industrial applications.

Currently, agricultural systems are inadequate to meet the demand of the population, coupled with the constant degradation of natural resources. Therefore, it is necessary to explore alternatives to increase the productivity and quality of crops with minimal environmental impact. The use of plant growth-promoting bacteria can provide solutions to some agri-environmental problems and replace or minimize conventional agricultural practices. In this study, a Bacillus pumilus strain with plant growth-promoting properties was isolated from mature compost. In vitro, the ability of Bacillus pumilus to solubilize phosphate, inhibit the growth of phytopathogenic fungi, and its effect on the germination of tomato and lettuce seeds was evaluated. In vivo, its effect on stem thickness, height, and the number of leaves of tomato and lettuce seedlings was studied. The results show that, in vitro, Bacillus pumilus solubilizes phosphate, inhibits the growth of the fungus Fusarium oxysporum, and increases the germination percentage of tomato seeds. The results, in vivo, demonstrate that the bacteria increases the stem thickness of tomato seedlings, while, in lettuce, it increases the stem thickness and the number of leaves. The outcome implies that Bacillus pumilus has properties as a plant growth promoter and can be used as a promising inoculant to enhance the growth of tomato and lettuce seedlings.