Summary -A proline lminopepndase activity was round in P shermanii 13673. The enzyme activity was present in the intracellular fraction. The peptidase was purifisd approximately 80 times by ionexchange chromatography on Fractogel T8K DEAE 650 and gel filtration on 8ephacryl 8-100 HR. The purified enzyme appeared as a single band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It had a molecular weight of 61 000. Optima for activity of the.purified enzyme were 40 oC and pH 8.0. The enzymatic activity was inhibited by phenylmethylsulfonylfluoride (1 mM). Divalent ions Zn, Co, Cu and Fe alsohad an inhibitor}t effect. The peptidase hydrolyzed specifically Pro p-NA amino acid, dipeptides Pro-Met, Pro-Phe, Pro-Le, Pro-lieu, Pro-G1yand 13-casomorphin des-Tyr fragment 7.

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SummarySurvival or inactivation of hum an and animal viruses III food, water, wastes has been studied extensively.In France, the most popular varieties of cheese, such as Camembert, Brie, Coulommiers are still prepared with raw milk, out side of heat-treated milks. These soft cheeses make up 31 % of ail cheeses consumed. 354000 tons were manufactured in 1985. Consumption is regularly increasing by 2 % each year.We studied the stability of 2 bovine enteroviruses: rotavirus and coronavirus, suspended in raw and sterilized bovine pre-cheese milks. The conditions of temperature, pH, rennet action and sodium chloride concentration examined in this study are those used routinely in the manufacture of soft cheeses.The 2 viruses have a remarquable stability to low temperatures, acid pH, calf rennet and sodium chloride. The results are suggestive of a possible viral persistence in soft cheeses prepared with raw or heat-treated bovine milks.

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After experimental contamination of bovine raw and heattreated milks with bovine rotavirus and coronavirus strains, we observed a strong viral inhibition only with raw milks, from which virus recovery was 5 x 10^%. Between 30% and 80% of the virus was recovered from the heat-treated milks, depending on the level of inoculation. The antiviral substance is heatlabile (destroyed within 30 min at 100°C), precipitated by ammonium sulfate and filtrable (0.45 fjim Millipore membrane). It also has neutralizing activity on tissue culture. Preparation of virus stocksBovine rotavirus. Strain RF 45, was kindly supplied by J. Laporte. Briefly, the MA 104 monolayers were washed with MEM and incubated for 3 h at 37°C. The rotavirus strain was inoculated at a low multiplicity of infection (MOI): 0.1 plaqueforming unit/cell (PFU); after 1 h of adsorption, MEM containing 10 (xg of trypsin/ml, and 0.16% tryptose phosphate broth was added. After complete cytopathogenic effect (CPE), cells were disrupted by three cycles of freezing-thawing. The viral suspension was centrifuged, then the supernatant liquid was filtered through a 0.22-fjun Millipore membrane. The virus stock was stored at -20°C, in 1-ml tubes. The final titer was estimated at 4 x 10 9 PFU/ml. Bovine coronavirus. Strain G 110, was kindly supplied by J. Laporte. The HRT 18 monolayers were washed with RPMI. The coronavirus strain was inoculated at MOI: 0.1 PFU/cell. After 1 h of adsorption, the maintenance medium was added.