Investigations into the heat stability of bacterial proteases and lipases.First notice: Proteases

Heated proteases of 32 strains of 10 species (Aeromonas hydrophila, Aeromon as caviae, Bacillus cereus, Bacillus subtilis, Clostridium perfringens, Pro teus mirabilis, Proteus vulgaris, Pseudomonas aeruginosa, Pseudomonas fluor escens and Serratia marcescens) were tested on their remaining proteolytic activity under the influence of different incubation temperatures (2, 7 und 30 degrees C). For detection of the proteolytic activity a modified agardi ffusion test was used. The substrate was gelatin. Loss of activity of all p roteases investigated could be observed under defined heat treatments (60'/ 60 degrees C, 30'/65 degrees C, 15'/71 degrees C. 5'/75 degrees C). But-une xpectedly - often a high enzyme activity was still detectable. There are sp ecies-specific proteolytic differences in thermoresistance. Proteases of Ps eudomonas spp., Aeromonas hydrophila and Serratia marcescens showed the hig hest heat resistance. In low heated, chilled stored food the effect of Baci llus cereus-, Bacillus subtilis-, Proteus vulgaris-, Proteus mirabilis- and Aeromonas caviae-proteases should be taken into consideration. According t o the results Clostridium perfringens proteases in this respect are less im portant.