Five psychrophilic Antarctic bacteria have been selected for their capacity to secrete exoenzymes into culture medium. These strains are able to grow from 0 to about 25° C. However, production of lipase fromMoraxella, α-amylase fromAlteromonas haloplanctis, β-lactamase fromPsychrobacter immobilis and protease fromBacillus is maximal at temperatures close to that of their environment (—2 to 4° C) and is strongly inhibited at higher temperatures. This thermal effect involves alterations in the secretory pathway in the upper range of temperatures, losses due to the enzyme thermal lability and in some cases to reduction in cell development. The apparent optimal activity temperature of these enzymes is between 30 and 40° C, i.e. about 20° C lower than that of their mesophilic counterparts.