A microbial exopolysaccharide alternan with emerging roles in food systems and outlook for industrial advancements

• Alternan is a unique exopolysaccharide with low viscosity, high solubility, and thermal stability. • It functions as a prebiotic, emulsifier, fat reducer, thickener, and edible film in food. • Produced by Leuconostoc mesenteroides strains using sucrose fermentation. • Purification utilizes ethanol, enzymes, and chromatography due to issues with dextran contamination. • Challenges: high costs, limited strains, regulatory limitations; requires further research for industry use. Alternan is a high-molecular-weight biopolymer that is structurally distinctive and generally synthesized by Leuconostoc . It comprises alternate α-1,3 and α-1,6 glycosidic linkages and displays diverse functional properties, like low viscosity, high water solubility, strong resistance to enzymatic degradation, and high thermal stability. These properties differentiate alternan from other polysaccharides, thus exhibiting its potential for a wide range of industrial applications. In the food sector, alternan acts as a multifunctional component, as a natural thickener, fat or calorie reducer, film-forming agent, prebiotic, emulsifier, and stabilizer. Its incorporation into food formulations and packing systems can reduce dependence on synthetic additives, minimize environmental impact, and promote eco-conscious, bio-based alternatives in the food industry. Alternan is extracted from fermentation broth through ethanol precipitation, further their structural properties are characterized by Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, Scanning Electron Microscopy (SEM), and ¹H/¹³C Nuclear Magnetic Resonance (NMR) spectroscopy. Despite their merits, the industrial application of alternan still remains underutilized due to lower product yield, higher production and purification costs, a lack of understanding about how its structure affects its function, and the absence of regulatory validation. Recent advances in microbial strain engineering, mutagenesis, and process optimization have the potential to enhance production efficiency and scalability. To improve the texture, stability, and shelf life of products in the food industry, current research focuses on incorporating alternan into composite biopolymer systems and nanoencapsulation while maintaining the biodegradability. Alternan in food formulations and packaging systems can reduce dependence on synthetic materials, thereby minimizing environmental pollution and promoting bio-based alternatives in the food industry.