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An Improved Agar Medium for the Detection of Proteolytic Organisms in Total Bacterial Counts
Author(s) -
Martley F. G.,
Jayashankar S. R.,
Lawrence R. C.
Publication year - 1970
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1970.tb02208.x
Subject(s) - agar , casein , agar plate , proteolysis , food science , chromatography , precipitation , biology , chemistry , microbiology and biotechnology , bacteria , biochemistry , enzyme , genetics , physics , meteorology
Summary. An improved medium for the detection of proteolytic organisms has been developed by adding caseinate (1% w/v), citrate (0·015 m) and Ca 2+ (0·02 m) to Standard Methods Agar. Its greater sensitivity compared with existing milk agar media is related to its ability to detect the first stage of casein breakdown as shown by the formation of a white zone of precipitation. This results from the deposition of insoluble para‐caseins, mainly para‐ k ‐casein, which is readily detected in the transparent medium. The extent of proteolysis exhibited by an organism is reflected both by the size and type of precipitation zone forming round the colony. No significant difference was found between total counts of raw milk samples measured on the new medium and standard methods agar. The new medium can thus be used for the simultaneous determination of proteolytic and total bacterial counts.