In this study the activity of the @entity3793 decarboxylase (HdcA) of @entity5858 PRI60 was determined during growth and in crude enzyme preparations to evaluate its hazardousness in dairy products. The effect of different pH values, @entity1132 availability, @entity1219 concentration, and growth temperature on @entity112 production was evaluated in M17 medium during 168 h incubation. In each case, the production of @entity112 increased concomitantly with the cell number with a relatively small further rise during the stationary phase. In all cultures the maximum @entity112 levels were reached at the end of active growth. @entity112 was detectable (10 to 55 mg/L) even when growth was strongly inhibited. The HdcA enzyme in crude cell-free extracts was mostly active at acidic pH values common in dairy products. @entity1219 concentrations lower than 5% did not affect its activity. The enzyme was quite resistant to heat treatments resembling low pasteurization, but was inactivated at 75   C for 2 min. Given the features of the enzyme studied, efforts must be dedicated to a thorough risk analysis and development of strategies to contrast the presence of histaminogenic @entity5859 strains in products from raw or mildly heat-treated milk. PRACTICAL APPLICATION: During its growth @entity5858 can produce @entity112 over a wide range of conditions encountered in cheesemaking and cheese ripening. The @entity3793 -decarboxylase is even more active in cell-free extract and @entity112 can be accumulated independently of cell viability.

Effect of chemico-physical parameters on the XXXX decarboxylase (HdcA) enzymatic activity in @entity5858 PRI60.

@entity3793 :: ('CHEBI:27570', 'Chemical') :: ['histidine'] @entity1219 :: ('CHEBI:26710', 'Chemical') :: ['NaCl'] @entity5858 :: ('1308', 'Species') :: ['Streptococcus thermophilus'] @entity1132 :: ('MESH:D007785', 'Chemical') :: ['lactose'] @entity5859 :: ('2057', 'Species') :: ['S. thermophilus'] @entity112 :: ('MESH:D006632', 'Chemical') :: ['Histamine', 'histamine']
@entity3793 :: (CHEBI:27570,Chemical) :: ['histidine']
