Milk clotting enzyme from bacillus stearothermophilus

A large number of thermophilic bacilli were screened for their ability to produce extracellular milk clotting enzyme as well as protease activity. A potent strain exhibited high milk clotting activity with lower protease formation was identified and characterized as Bacillus stearothermophilus NRC 41. Optimum temperature and pH for milk clotting enzyme activity was found to be 65-70 degrees and 6.1 respectively. Maximum enzyme activity was obtained when CaCl2 was added to skim milk at a concentration of 125 mg/l. Maximum yield of enzyme was obtained after 48 hr of incubation at an initial pH of 7.0. From all carbon and nitrogen sources tested, lactose and NH4NO3 respectively were found to be the most suitable for enzyme formation. On the other hand, the presence of glucose, sucrose, fructose or raffinose as well as [NH4]2SO4, [NH4]3PO4 or NH4Cl in the medium resulted in suppressing enzyme formation

B-Glucosidase from yeasts

Thirty two yeast strains belonging to different genera were screened for their ability to produce beta-glucosidase. The qualitative analysis showed' that only seven strains [21.9%] exhibited highest productivity while quantitative assay proved that kluyveromyces fragilis NRRL Y-1137 was the most resuhful strain. In addition, its beta-glucosidase was successfully purified by fractional precipitation with acetone. On the other hand, the properties of the partially purified enzyme obtained were as follows: Optimum temperature of 50°, optimum pH value 6.2 and the rate of pNPG hydrolysis was linear up to 20 min under optimum assay conditions. Addition on cellobiosc or glucose to the reaction mixture decreased the enzyme activity. Furthermore, the enzyme was relatively more stable at pH 6.0-7.0 and rapidly inactivated at > 50°

Carbon sources influencing the production of cellulases and proteases by different cellulolytic microorganisms

Treated corn cobs cellulose [2%] was used as the only carbon source for the growth and production of extracellular cellulases and proteases by four cellulolytic microbes: Penicillium funiculosum, Phanerochaete chrysosporium, Micromonospora calcea and Trichoderma virideTViride and Pfuniculosum showed a great ability for the production of carboxy-methyl cellulase [CMCase], filter paper-ase [FPA], neutral and acid proteasesMaximum neutral protease activity was obtained with MCalcea and TvirideOptimum activities in relation to the incubation periods varied according to the enzyme studied and the organism testedThe effect of different carbon sources on cellulases and proteases production indicates that cellulose and lactose were good inducers for CMCase production by Pfuniculosum and PhChrysosporium respectivelyThe latter inducers were also the best for the production of neutral proteases by Tviride and Mcalcea respectively, while cellobiose and lactose were the best inducers for acid protease production by PFuniculosum and Phchrysosporium, respectively