Identification of a Bacterium Isolated from Raw Milk and Study on Its Heat-Stable Protease

Abstract:

UHT milk can be clotted or hydrolyzed by the heat-stable protease from Psychrotrophs bacteria in raw milk,resulting in bitter taste and other quality deterioration in shelf life.One of bacterium from raw milk was identified based on morphology,physiology,biochemistry analysis,16S rDNA and 16-23S rRNA sequence analysis.The bacterium(named Rm12) was identified as Pseudomonads fluorescens.The optimal catalytic temperature and pH of the protease from Rm12 were 40 ℃ and 6.8 respectively.After heat treatment(140 ℃,4 s),the rest of activity of protease was only 6.66% that of the original preparation.