Microbial welan gum production, chemistry and applications: A review

Welan gum, an extracellular polysaccharide produced by the Sphingomonas sp., has attracted considerable interest due to its distinctive properties and promising applications in adhesion, thickening, suspension, emulsification, stabilization, lubrication, and film formation. However, several unresolved issues related to welan gum, particularly its low biosynthesis efficiency, have hindered its widespread industrial application. This review first aims to provide a comprehensive overview of welan gum, focusing on its structure and development, the production strains, and biosynthesis pathways. To facilitate the industrial application of welan gum, we further summarize strategies, including optimizing fermentation conditions and engineering production strains to enhance yield, and discuss methods for the recovery and purification of welan gum based on existing literature. Then, we explore the relationship between the modification, structure, and properties of welan gum, emphasizing how these factors can enhance its functionality and application value. Furthermore, the review elucidates the behavior of welan gum in aqueous solutions, examining the impacts of pH, cations, temperature variations, and various additives. In conclusion, we provide a concise summary of the current applications of welan gum and present key research areas that warrant further investigation to advance its use in industry.