Screening, Identification and Fermentation Optimization of Aminotransferase-producing Strain / 微生物学通报

ABSTRACT

A strain named as WJ44 with capability of producing branched-chain aminotransferase was isolated from the soil, the enzyme activity is especially high when used leucine as a substrate. According to the physiological characteristics, biochemical characteristics and 16S rRNA sequence of WJ44, the strain was identified as Bacillus cereus. The optimal carbon source and nitrogen source were also determined as 20 g/L glucose, 15 g/L tryptone and 5 g/L beef extract, respectively. The optimal proportion of other component in the medium is corn steep liquor 15 g/L, KH2PO4 3 g/L, MgSO4?7H2O 0.5 g/L. The optimum original pH value is 7.0, the cultural temperature is 37℃, liquid volume is 20 mL/250 mL, the shaker’s rotating speed is 200 r/min. The highest leucine transferase activity of 45.787 U/mL was achieved after 10 h under the opti- mal condition, and the dry weight of cell is 8.643 g/L, increased by 54% and 10% respectively. This result shows that WJ44 is a branched-chain aminotransferase-production strain with fine capability.