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Storage of Lactic Streptococci. II. Proteinase Synthesis Following Storage in Phosphate Buffer¹

Department of Plant Pathology and Bacteriology West Virginia University, Morgantown

ABSTRACT

The stability and synthesis of the extra-cellular proteinase of Streptococcus lactis N-2 were studied following storage of the cells in 0.05 M phosphate buffer at pH 8.5 and pH 4.5. Rapid inactivation of the residual proteinase was observed under both conditions within the first six days of storage. The amount of proteinase synthesized during the first three hours of growth in milk by the cells stored at pH 8.5 decreased with length of storage and was negligible by the tenth day. The cells stored at pH 4.5 exhibited an increased capacity for proteinase synthesis up to the fourth day of storage; thereafter, the amount of enzyme synthesized decreased. When results were correlated with culture viability and acid production under the two conditions of storage, no relationship was found between culture activity and proteinase activity. A number of factors are suggested which might contribute to the over-all activity of a culture besides that of its extracellular proteinase.

¹ Published with the approval of the Director of the West Virginia University Agricultural Experiment Station as Scientific Paper No. 1032.