PURPOSE: To obtain sarcosine oxidase extremely useful as an enzyme for determining creatinine or creatine in blood and urine at a practical level by culturing UTK3044 strain belonging to the genus Bacillus in a synthetic medium or natural medium.

CONSTITUTION: UTK3044 strain (FERM P-10849) is cultured in a medium capable of growing the strain, namely a synthetic medium or natural medium containing a carbon source, a nitrogen source, an inorganic salt and another nutrient. The culture temperature is usually 30-50°C, preferably about 40°C. pH of the culture solution is 6.5-8.0. Shaking culture or aerated spinner culture is carried out under the above-mentioned condition for 5-18 hours to efficiently produce sarcosine oxidase (SAO) in the culture mixture with growth of the bacteria. The SAO has physical and chemical properties shown by table 1.