Escherichia coli Nissle 1917 (Mutaflor)

Escherichia coli Nissle 1917 (EcN) is a probiotic bacterium, not a conventional food ingredient, so it does not contribute macronutrients (carbohydrates, fats, proteins) or micronutrients in meaningful dietary quantities at therapeutic doses. Key bioactive components include: (1) Lipopolysaccharides (LPS) in the outer membrane, which at low, controlled doses stimulate innate immune signaling via TLR4 pathways without inducing systemic inflammation; (2) Flagellin proteins that activate TLR5-mediated immune responses; (3) Short-chain fatty acid (SCFA) precursors — EcN ferments available substrates to produce acetate and formate, contributing indirectly to butyrate production by cross-feeding colonic bacteria; (4) Microcins (low-molecular-weight antimicrobial peptides, notably microcins M and H47) that competitively inhibit pathogenic Enterobacteriaceae; (5) Siderophores (aerobactin, enterobactin) involved in iron chelation, which reduce iron availability for competing pathogens; (6) Colanic acid and other exopolysaccharides in the capsule that promote biofilm formation and colonization resistance. Typical therapeutic dosage in commercial Mutaflor capsules is 2.5×10^8 to 25×10^9 CFU per capsule. Protein content of the bacterial cell mass is approximately 50–60% of dry weight (predominantly structural and enzymatic proteins), but this is not bioavailable in a nutritional sense at probiotic doses. Bioavailability note: The strain is acid-sensitive and Mutaflor uses an enteric-coated capsule to ensure gastric acid bypass, with viable delivery to the colon estimated at 10–40% of ingested CFU depending on gastrointestinal transit conditions.