Cold-adapted enzymes possess high specific activity at low and moderate temperatures with respect to their mesophilic and thermophilic homologs; it is accepted that they have a less rigid and more flexible structure in the region surrounding the active site. However, the low stability of such molecules could represent the main barrier for their application in some industrial bioprocesses. The aim of this article was to investigate the ability of the naturally occurring osmolytes to increase the thermal stability and the specific activity of the cold-active lipase from Psychrobacter sp. TA144 (PsyHSL), which belongs to the hormone-sensitive lipase group. The effect of trimethylamine N-oxide (TMAO), betaine, and L-proline addition on the activity and thermal stability of PsyHSL was investigated by means of biochemical and biophysical techniques. It turned out that in the presence of 3 M TMAO, the enzyme specific activity enhanced up to 250% at 50 degrees C, while the addition of 1 M TMAO increased the thermostability fivefold at 45 degrees C. Our experiments demonstrated that, even in the case of a psychrophilic enzyme, osmoprotectants, particularly TMAO, addition may be considered an efficient strategy to improve the protein thermal stability and specific activity at higher temperatures. (c) 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 946952, 2012