Extracellular protease production by dairy strains of Aeromonas hydrophila as affected by growth media and incubation temperature

Author: Santos J.A.   Gonzalez C.J.   Lopez-Diaz T.M.   Garcia-Lopez M.L.   Otero A.  

Publisher: Academic Press

ISSN: 0740-0020

Source: Food Microbiology, Vol.13, Iss.1, 1996-01, pp. : 47-51

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Abstract

The production of extracellular proteases by two strains of Aeromonas hydrophila of dairy origin was determined in two media at two different temperatures. With one exception (strain QV12 in skim milk agar), the specific proteolytic activity (OD at 440 nm mg protein) of extracellular products of each A. hydrophila strain was higher at 4#°C than at 28#°C. Also, the addition of skim milk to the culture medium increased the specific proteolytic activity of the extracellular products for each A. hydrophila strain at both temperatures (except strain QV12 at 4#°C). Ten electrophoretic bands showing proteolytic activity were detected, and none of these was similar to previously described proteases of A. hydrophila . The number of electrophoretic bands showing protease activity was higher when strains were grown in skim milk agar than in brain heart infusion agar, with the temperature of incubation showing a minor effect on the types of proteases produced by the two A. hydrophila strains. These data suggest that the regular presence of A. hydrophila in milk and dairy products may not be underestimated because milk could act as stimulant to the production (by A. hydrophila strains of dairy origin) of extracellular proteases associated with undesirable effects (spoilage, pathogenesis).