Lipase from the thermotolerant fungus Rhizopus homothallicus is more thermostable when produced using solid state fermentation than liquid fermentation procedures

Extracellular lipases were obtained from solid (SSF) and submerged (SmF) thermotolerant Rhizopus homothallicus fungus cell cultures and purified to homogeneity. The two enzymes are monomers having a molecular mass of 29.5 kDa and an identical protein structure, since the N-terminal sequences and peptide maps were identical. However, some of their properties are different, namely the specific activity on trioctanoin (8600 U/mg with SmF and 10,700 U/mg with SSF), the temperature at which maximum activity occurs (30 degrees C with SmF and 40 degrees C with SSF) and the thermal stability (half-lives at 50 degrees C of 0.44 h with SmF and 0.72 h with SSF). These differences between the kinetic properties suggest that when they were tested, one or both fungal lipases might still have been associated with non-proteic compounds originating from the culture medium. (c) 2006 Elsevier Inc. All rights reserved.