Welan gum is an exopolysaccharide

Exopolysaccharide

Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharides including intracellular polysaccharides, structural...

 used as a rheology

Rheology

Rheology is the study of the flow of matter, primarily in the liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force....

 modifier in industrial applications such as cement manufacturing. It is produced by fermentation

Fermentation (biochemistry)

Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...

 of sugar by bacteria of the genus Alcaligenes

Alcaligenes

Alcaligenes is a genus of Gram-negative, aerobic, rod-shaped bacteria. The species are motile with one or more peritrichous flagella.Alcaligenes species have been used for the industrial production of non-standard amino acids; A. eutrophus also produces the biopolymer polyhydroxybutyrate .-External...

. The molecule consists of repeating tetrasaccharide units with single branches of L-mannose or L-rhamnose. In solution, the gum exhibits viscosity retention at elevated temperature, and is stable in a wide pH range, in the presence of calcium ion, and with high concentration of glycols.