Abstract: The lyophilized extracellular mucilage (LEM) extracted from Kebsiella oxytoca CF154 was subjected to a series of toxicological tests to evaluate its safety for use in various foods in the future. LEM was examined for acute and subchronic oral toxicity by using Wistar rats, and for mutagenic potential by using the Ames test using Salmonella typhimurium, and the micronucleus test by using male ICR mice. No evidence was obtained showing acute oral toxicity at a LEM concentration from 0.1% to 3.0% (w/w) in this test, nor was there any mutagenicity exhibited up to a concentration of 3.0% with and without metabolic activation (S-9 mixture). The micronucleus test showed no obvious positive response either. Using LEM as a dietary mixture at levels of 1.0%, 2.0%, and 3.0% (w/w) for feeding the rats for 12 weeks did not show any inducible signs of toxicity. The result of this study indicates that there is a lack of toxicity and supports the use of LEM extract from K. oxytoca CF154 under a concentration of 3.0% or less for a variety of foods.