الفهرس 
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Abstract
The aims of this work are to study the production, purification, nutritional and environmental factors for maximum protease production and some characteristics of protease from some proteolytic bacterial strains, then using produced enzyme to accelerate Domiati cheese ripening.
Part (1):
1.Screening studies on sixty isolates of bacteria from different environments for extracellular protease production have revealed, two highly protease-producing isolates, identified as Bacillus subtilis M14 and Bacillus coagulans M53 which were selected and used in this
investigation.
2.Both strains were examined for their protease activity on seven culture media. The two strains gave maximum protease production on Malik and Mathur medium.
3.Sucrose (at 0.5%) was the most suitable carbon source for enzyme production by B. coagulans M53, while control followed by maltose seemed to be the most suitable carbon
source for B. subtilis M14.
4.Tryptone (1%) and peptone (0.5%) were the most nitrogen sources for the highest level of protease secretion by B. subtilis M14 and B. coagulans M53, respectively.
5.The optimum incubation temperature for maximal protease production was 30°C and 35°C for B. subtilis M14 and B. coagulans M53, respectively.
Summary and Conclusion
6.The optimum initial pH for maximum protease production by the two strains was pH 7.0.
7.The optimum incubation period for protease production by both Bacillus strains was 3 days.
8.The ratio of 4: 1 air: medium (50 ml medium in 250m1 Erlenmeyer flask) was the optimum ratio for protease production by B. subtilis M14. While, 3:2 air: medium (100 ml medium in 250m1 Erlenmeyer flask) was the most suitable ratio for B. coagulans M53.
9.The modified Malik and Mathur medium was prepared and inoculated with standard inoculum of 24 hr. old culture of each of Bacillus subtilis M14 and Bacillus coagulans M53, then incubated on the optimum conditions for maximum protease production.
10.The produced enzyme when precipitated at any percentage of acetone gave a slight enzyme recovery. By increasing acetone concentration, specific activity of protease and recovery percentage increased. The highest protease activity, specific activity and recovery, were at the 60% saturation of acetone for both supernatant of Bacillus subtilis M14 and Bacillus coagulans M53 cultures. Recovery was 48.38% and 51.99% for the two strains respectively.
11.Proteases of both Bacillus subtilis M14 and Bacillus coagulans M53 were purified by the convential methods like acetone fractionation and sephadex-gel filtration. The fractions from number 15 to number 39 and fractions from number 21 to number 36 contain almost all the proteolytic
Summary and Conclusion
activity for proteases of Bacillus subtilis M14 and Bacillus coagulans M53 respectively. The recovery yield was about 70.35% and 69.7% for proteases of both Bacillus subtilis M14 and Bacillus coagulans M53 respectively.
12.The optimum temperature for Bacillus subtilis M14 and Bacillus coagulans M53 protease activities was 35°C and 30°C, respectively.
13.The activities of the two enzymes decreased and most activity was lost at 60°C for 15 min. The retained activities were 23.2% for B. subtilis M14 and 14% for B. coagulans M53 proteases. While treatment at the same temperature for 30 min. markedly decreased the activity of B. coagulans M53 protease. In addition, sharp decrease in the activity of both proteases was noticed after 60 min. Results also showed that Bacillus subtilis M14 protease maintained with activity higher than that noticed for the protease of Bacillus coagulans M53.
14.The activity of both proteases increased as the pH increased reaching the maximum at the range of pH 7.0 - 8.0 for both B. subtilis M14 and B. coagulans M53. The activities of the two enzymes were slightly decreased since the retained activity was 48.8% for protease of B. subtilis M14 and 30.7% for protease of B. coagulans M53 when incubated for 15 min at pH 9.0. The enzyme recovery was at the same level for Bacillus subtilis M14 protease when incubated at the same pH for 30 and 60 min. And at the same level for Bacillus coagulans M53 protease when incubated at the same pH for 30 min.