PURIFICATION AND PARTIAL CHARACTERIZATION OF A 1.57 KDA THERMOSTABLE ESTERASE FROM BACILLUS-STEAROTHERMOPHILUS

The molecular mass of esterases usually falls in the range of 20-160 k Da, although an esterase of 5.7 kDa from Candida lipolytica has been d escribed. Three other enzymes smaller than 10 kDa have been reported, all of which were more thermostable than their higher molecular mass c ounterparts. This paper describes the purification of an extracellular esterase hydrolysing fluorescein dibutyrate from Bacillus stearotherm ophilus NCIMB 13335. The esterase had a molecular mass of 1.57 kDa whe n analysed by SDS-PAGE, gel filtration and MALDI-TOF spectrometry. Thi s enzyme retained more than 90% of its activity after incubation at 90 degrees C for 2 h.