PROTOLYTIC ACTIVITY OF CERTAIN STRAINS Of BACILLUS SPP. USED AS SUBSTITUTE FOR BUFFALOES MILK CLOTTING

Abstract

The protolytic activity of 14 strains of Bacillus spp isolated from milk samples collected from different governorates in Egypt was evaluated . The strains were inoculated in pasteurized buffaloes milk incubated at 30 o C for 5 hours .Acidity, pH ., soluble nitrogen ( SN) and non protein nitrogen (NPN) as % of total nitrogen (TN) were determined during the incubation period . The tested strain showed a wide range of protolytic activity as indicated by the rate of soluble nitrogen ( SN) and non protein nitrogen (NPN) contents during incubation . The strain No 4,6 and 8 coagulated milk after 2 hours of incubation and showed the highest levels of both SN and NPN content . So these strains could be recommended the production of milk clotting enzyme .The inhibitory affect of Lactobacillus acidophilus , Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei subsp. casei on Bacillus were evaluated use by diffusion method on nutrient agar media for the fourteen Bacillus spp. It was found that the inhibtory of Lactobacillus acidophilus was more than Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei subsp. casei except on B . sphaercus . The inhibitory effects of L. acidophilus ; L. delbrueckii subsp. bulgaricus and Lactobacillus casei subsp. casei was the same. Further mores the effect of heat treatment within the temperature range of 85-135 o C. , and various exposure times was studied . The highest resistance was found in case of B . amyloliquficans spores , which survived the temperature of 135 o C. the greatest reduction of spore numbers was found for B .cereus .