Staphylococcus cohnii HFUTY-08: a novel acid urease-producing strain

Urea in alcoholic beverages is a precursor of ethyl carbamate (EC), which is carcinogenic. At present, removal of urea by acid urease is considered to be the most effective method. In this study, a strain with higher acid urease production was screened and the enzyme activity was 1.12 U/mL. The strain was identified as Staphylococcus cohnii via a phylogenetic analysis of its 16S rDNA gene sequence, its morphological characteristics, and its physiological and biochemical properties, named as Staphylococcus cohnii HFUTY-08. Optimum culture conditions were determined through a single-factor test and an orthogonal test, with results as follows: glucose concentration 30 g/L, peptone concentration 15 g/L, initial pH 5, and an optimal inoculation amounts of 5%. Under these conditions, the activity of acid urease produced by strain Staphylococcus cohnii HFUTY-08 was 1.78 U/ml. Besides, the crude enzyme was purified to electrophoretic homogeneity by ion exchange chromatography and gel filtration chromatography. The molecular weight of the enzyme was estimated to be 295 kDa and the structural features of the enzyme were defined as (alpha beta gamma)(3). Finally, the preliminary study on the removal of urea by acid urease in Chinese rice wine (CRW) showed that the enzyme could remove about 75% urea within 72 h at 37 A degrees C, which effectively prevented EC production.