Amongst more than 1000 isolates collected in various cold environments, the strain Arthrobacter psychrolactophilus Sp 31.3 has been selected for its ability to grow and to produce exoenzymes at low temperatures, its inability to grow at 37 degrees C, its non-halophilic character and its growth versatility on various media. This non-pathogenic strain displays a strong resistance to desiccation and storage at room temperature and is suitable for the production of freeze-dried bacterial starters. When grown in a synthetic wastewater at 10 degrees C, the strain induces a complete clarification of the turbid medium and efficiently hydrolyses proteins, starch and lipids in the broth. Furthermore, this strain has a remarkable capacity to improve the biodegradability of organic compounds in wastewater as indicated by a BOD(5)/COD ratio of 0.7.