Reihaneh Nikbakhti - Department of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
Bahar Shahnavaz - Department of Biology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
Ahmad Asoodeh - Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran

Cold-active proteases constitute an important group of these enzymes; have high-catalytic efficiencies at lower temperature and lower thermal stability. Numerous studies have indeed shown that cold-active proteases are gen-erally characterized by higher turnover numbers (kcat) and catalytic efficiencies (kcat/Km) at low temperatures(<10 ◦C) compared to their mesophilic counterparts. Alkaline proteases from bacteria find numerous applications in various industrial sectors and different companies worldwide have successfully launched several products based on alkaline proteases. In this presence, protease producing bacteria was tested by halo zone in mineral salt agar containing skim milk. Enzyme production was determined using optical density. The enzyme production was measured in different temperatures (15, 20, 25, 30 and 37 °C). The impact of different nitrogen sources (yeast extract and skim milk) and concentrations (0.5, 1, 1.5 and 2%) was investigated. About 53% of the isolates showed a zone with a mean diameter of 2.14 mm, with 3 mm as the high diameter. The high enzyme production was obtained about 0.312 unit/ml. The highest level of protease production was obtained at 20 °C temperature (0/312 Uml-1). The protease production was increased by adding skim milk as a nitrogen source (0.594 Uml-1). The preliminary results showed that cold active indigenous bacteria are remarkable for enzyme production. These strains can potentially be used for the production of enzymes in various industries. Cold-adapted proteases thus can be use to optimize industrial processes with less energy inputs and process cost by removing the cost of heat inactivation step

protease, optimization,Skim Milk, Nitrogen