Galactose joined to glucose by a $eta(1 ightarrow4)$ glycosidic bond makes lactose and this disaccharide is rich in milk. It is known that lacotse is hydrolyzed to each monomeric sugar by either lactase in human or $eta-galactosidase$ in bacteria. Ingestion of milk by lactase-deficient persons causes a temporary diarrhea and subsequent chronic diarrhea results in colitis with chronic inflammation. We isolated a $eta-galactosidase$ producing psycrotolerant strain AS-20 from near cattle shed and investigated the growth at various temperature conditions. Whereas Escherichia coli strains did not grow at $10^{circ}C$, the AS-20 strain could grow well at this low temperature and showed optimal growth at $30^{circ}C$. The isolated strain was identified as 97% Hafnia alvei by biochemical properties. This strain could ferment glucose, lacotse, maltose, mannitol, xylose, ONPG, rhamanose and L-arabinose, and decarboxylate lysin and ornithine. To confirm the identity of isolated strain we amplified 16S rDNA by PCR and searched similarity of the 1426 bp DNA sequcence with Genbank database. The strain AS-20 showed 99% similarity with Hafnia alvei. The activity of $eta-galactosidase$ was 1.5 times higher when the cell was grown at 10 or $20^{circ}C$ than at $30^{circ}C$. The highest enzyme activity of AS-20 was also much higher than that of E. coli, which was grown at $30^{circ}C$.