A gene encoding a carboxylesterase produced by Geobacillus thermoleovoras CCR11 was cloned in the pET-3b cloning vector, sequenced and expressed in Escherichia coli BL21(DE3). Gene sequence analysis revealed an open reading frame of 750 bp that encodes a polypeptide of 250 amino acid residues (27.3 kDa) named CaesCCR11. The enzyme showed its maximum activity at 50 °C and pH 5-8, with preference for C4 substrates, confirming its esterase nature. It displayed good resistance to temperature, pH, and the presence of organic solvents and detergents, that makes this enzyme biotechnologically applicable in the industries such as fine and oleo-chemicals, cosmetics, pharmaceuticals, organic synthesis, biodiesel production, detergents, and food industries. A 3D model of CaesCCR11 was predicted using the Bacillus sp. monoacyl glycerol lipase bMGL H-257 structure as template (PBD code 3RM3, 99 % residue identity with CaesCCR11). Based on its canonical α/β hydrolase fold composed of 7 β-strands and 6 α-helices, the α/β architecture of the cap domain, the GLSTG pentapeptide, and the formation of distinctive salt bridges, we are proposing CaesCCR11 as a new member of family XV of lipolytic enzymes.
Keywords: Carboxylesterases; Family XV; Geobacillus; Lipases; Thermophiles.