A milk-clotting enzyme from Bucillirs sirhrilis K-26 was purified by gel filtration and ion-exchange chromatography resulting in a 24-fold increase in specific activity with an 80% yield. Polyacrylamide gel electrophoresis and ultracentrifugal analysis revealed that the purified enzyme was homogeneous and had a molecular weight of 27,000 and a K , of 2.77 mgiml for K-casein. The enzyme was most stable at pH 7.5 and showed increasing clotting activity with decrease in milk pH up to 5.0. The maximum milk-clotting activity was obtained at 60°C. but the enzyme was inactivated by heating for 30 min at 60°C. The enzyme was irreversibly inhibited by EDTA and unaffected by DFP. Heavy-metal ions (Hg2+, Pb2+) inactivated the enzyme.

No abstract

An attempt was made to find out the optimum aeration and agitation rates on the production of bacterial rennet from Bacillus subtilis K-26 using 5y0 wheat bran medium in a 13 liter fermentor. The enzyme activity and the growth rate were shown to increase with an increase in the rate of agitation. The fermentation experiments carried out at an agitation rate of 400 rpm showed an approximate threefold increase in enzyme activity with a considerable decrease in the fermentation time over those agitated a t 200 and 300 rpm. The beneficial effect of a higher oxygen rate was observed for enzyme production occurring a t a lower agitation rate. The inoculum activity and the varying amounts of antifoam agent which were added showed no apparent effect either on the total incubation time or on the final enzyme activity. It has been suggested that an agitation rate of 400 rpm with an aeration level of 3000 cc/min are the optimum values for the efficient production of bacterial rennet from B. subtilis K-26 using 5% wheat bran medium in a 13 liter fermentor.

An intracellular proteinase from Streatococcus cremoris was isolated, partially purified and characterized. A 40‐fold purification was obtained with retention of 73% of the original activity. The proteinase exhibited normal reaction kinetics with respect to enzyme concentration and reaction rate. Proteinase activity was optimal at pH 7.0 and 37°C. The enzyme showed maximum activity on casein, the alpha casein being preferentially degraded. Effect of metal ions, some inhibitors and reducing agents were studied.

Aspergillus parasiticus NRRL 2999 and Aspergillus flavus K3 were examined for aflatoxin production in khoa. The inoculated khoa samples were examined after incubation for 2 weeks at 5, 28 and 37 C. Aflatoxin penetrated to a depth of 4 cm in the inoculated khoa samples stored at 28 and 37 C.