Levan is a natural polymer made entirely of fructose (fruit sugar) molecules linked together in long chains. It belongs to a family of carbohydrates called fructans, and it’s produced by dozens of bacterial species as well as some plants. What makes levan increasingly interesting to food scientists, pharmaceutical researchers, and cosmetic formulators is its unusual versatility: it can thicken foods, moisturize skin, feed beneficial gut bacteria, and even serve as a drug delivery vehicle.
How Levan Is Built
At the molecular level, levan is a chain of fructose units connected by a specific type of chemical bond called a beta-2,6 linkage. This distinguishes it from inulin, the other well-known fructan, which uses beta-2,1 linkages instead. That single difference in how the fructose units connect gives the two polymers distinct physical properties and biological behaviors.
Levan chains vary enormously in size. Small versions weigh around 12,500 daltons (a unit of molecular mass), while the largest microbial levans reach into the billions of daltons, making them some of the biggest carbohydrate molecules found in nature. The size of the chain matters: smaller levans dissolve more easily and behave differently in the body than their giant counterparts.
Where Levan Comes From
Bacteria are the primary levan factories. Species from the genera Bacillus, Lactobacillus, Pseudomonas, Streptococcus, Xanthomonas, and Zymomonas all produce levan, typically secreting it as a slimy coating on their outer surface. These bacteria manufacture levan using an enzyme called levansucrase, which takes ordinary sucrose (table sugar), snaps it apart, and repeatedly attaches the freed fructose units onto a growing chain. Glucose is released as a byproduct each time a fructose unit is added.
The enzyme can work in two modes. In the processive mode, it holds onto a single chain and keeps extending it, producing very large levan molecules above 2,000,000 daltons. In the nonprocessive mode, the enzyme picks up and releases chains freely, yielding smaller molecules. Certain plants also produce beta-2,6 fructans, though microbial production is the main route used commercially because bacteria can churn out large quantities from inexpensive sucrose feedstocks.
Levan in Food Products
In the food industry, levan works as an emulsifier, stabilizer, thickener, and fat substitute. It can replace some of the fat in processed foods while still providing a satisfying texture, and it contributes dietary fiber that supports digestion.
Yogurt is one concrete example. Adding just 0.2 to 0.5% levan to fermented yogurt increased the product’s water-holding capacity above 77%, outperforming standard fructooligosaccharides on both stability and moisture retention. The added levan also boosted the growth and survival of the two bacterial cultures most commonly used in yogurt production. Beyond dairy, levan shows promise as a flavor and fragrance carrier, a sweetener, and a source of shorter fructooligosaccharides that can be used as functional ingredients on their own.
Prebiotic Effects on Gut Bacteria
Levan acts as a prebiotic, meaning your own gut bacteria can ferment it and use it as fuel. When researchers grew human fecal bacteria on levan in the lab, the microbes produced a mix of acetic, lactic, butyric, propionic, and succinic acids, all short-chain fatty acids that play important roles in gut health. Acetic and lactic acids were the dominant products, with butyric and propionic acids produced at roughly one-third to one-half the level.
The fermentation process involves a kind of teamwork among different bacterial species. Bacteroides and certain Lactobacillus species break down the levan chains first, releasing fructose and shorter fragments. Other bacteria then consume those fragments. Notably, Faecalibacterium, a genus widely considered a marker of a healthy gut, thrived in levan-supplemented cultures. So did Roseburia and Catenibacterium, both of which produce butyrate, a short-chain fatty acid that nourishes the cells lining the colon. Bifidobacteria and members of the Enterobacteriaceae family also grew on levan, particularly when amino acids were available alongside it.
Immune System Effects
A growing body of evidence suggests levan can influence immune function. In animal studies, dietary levan from Zymomonas mobilis (a molecular weight of about 700,000 daltons) increased the number of white blood cells in pigs while reducing blood levels of two key inflammatory signals, IL-6 and TNF-alpha. The same dietary treatment increased Lactobacillus levels in the animals’ feces, pointing to overlapping gut and immune benefits.
Levan from Bacillus species isolated from honey helped alleviate gastric ulcers in animal models and reduced the activity of NF-kB, a protein complex that drives inflammation, in stomach tissue. The size of the levan molecule appears to influence the strength and type of immune response it triggers, with different molecular weights activating immune signaling pathways to different degrees.
Skincare and Cosmetics
Levan has antioxidant properties, boosts skin hydration, and is nontoxic to human cells, which makes it appealing for cosmetic formulations. In body wash products, replacing a portion of the water content with a levan-rich extract reduced the skin-irritating effect of the entire formulation. The likely explanation: levan molecules absorb free surfactant particles (the cleaning agents in soap), pulling them out of the liquid and reducing their contact with the skin’s surface.
The same levan-containing formulations showed over 40% less ability to strip away the skin’s natural oils compared to standard versions. That translates to less dryness after washing. The effect grew stronger at higher levan concentrations, suggesting it is directly responsible rather than a coincidence of the formulation. Cosmetic manufacturers also use levan in moisturizing creams and lotions, taking advantage of its film-forming properties to help lock water into the skin.
Drug Delivery and Medical Research
Levan’s ability to form stable coatings and its natural affinity for certain cell receptors have made it a subject of pharmaceutical research. One notable application involves coating tiny silica particle clusters with levan and loading them with a chemotherapy drug. These levan-coated nanoclusters released the drug in a controlled, sustained way under normal conditions. When ultrasound was applied, the release accelerated, giving researchers a way to trigger drug delivery at a specific tumor site.
In a mouse tumor model, the combination of levan-coated nanoclusters and ultrasound significantly reduced both tumor volume and tumor weight without causing the animals to lose body weight, a common sign of toxic side effects. The levan shell helped direct the drug to cancer cells that overexpress a particular fructose transporter on their surface, essentially exploiting the cancer cells’ sugar appetite to deliver a targeted dose of chemotherapy.
How Levan Differs From Inulin
Inulin is the fructan most people have heard of, found in chicory root, garlic, and onions. Both inulin and levan are chains of fructose built from sucrose, and both are synthesized by related enzyme families (GH32 and GH68). The key structural difference is the bond angle: inulin uses beta-2,1 linkages, levan uses beta-2,6. This changes the shape of the molecule, which in turn changes how it dissolves, how quickly gut bacteria break it down, and how it interacts with the immune system.
In practical terms, inulin chains tend to be shorter (typically 2 to 60 fructose units) and are primarily sourced from plants. Levan chains can be vastly longer, reaching millions of fructose units when produced by bacteria. Inulin is already a mainstream prebiotic supplement and food ingredient. Levan is less commercially established but offers a broader range of functional properties, particularly its film-forming ability, immune-modulating effects, and potential in drug delivery systems that inulin does not share.