THE CHARACTERISTICS OF LIPASES OF PSYCHROTROPHIC YERSINIA, ENTEROBACTER AND CITROBACTER SPP OF DAIRY ORIGIN

Psychrotrophic Yersinia, Mig, Enterobacter M31 and Citrobacter M33 exh ibited maximum growth and lipase activity on third day of incubation a t 30 degrees C. The lipase activity with Yersinia sp. was the highest at both pH5.6 and pH 7.6. It was the highest at 7.6 and 7.0 with Enter obacter sp. and Citrobacter sp, respectively. The lipase of Yersinia a nd Enterobacter spp. was active in the temperature range of 7 degrees to 40 degrees C but the optimum temperature was at 30 degrees to 40 de grees C respectively. The lipase of Citrobacter sp. was active in the temperature range of 10 degrees - 40 degrees C with optimum activity a t 30 degrees C. EDTA treatment of the lipase activity of all the 3 cul tures appreciably reduced their activity. However, all the divalent me tal ions tested restored the activity of lipases of Yersinia and Citro bacter. But the activity in Enterobacter lipase was not restored. Heat ing to above 70 degrees C/10min completely destroyed the lipase activi ty of Yersinia and Enterobacter while the activity of Citrobacter redu ced to about 50% even after heating to 80 degrees C/10min.