Effects of curing agents and the stability of a glutaminase from Debaryomyces spp.

The stability of a glutaminase from Debaryomyces spp. CECT 11815 was studied. The enzyme showed poor stability at acid pH (half-life below 10 h at pH 5.5). Better stability was observed at pH 7.5–8.5; however, some variability was found, depending on the type of buffer used. The thermal stability of the glutaminase was rather poor at 37 °C (half-life of 7.4 h) but increased at lower temperatures, reaching a half-life of 323.2 h at 4 °C. EDTA and ethylene glycol extended the enzyme half-life while l-Asp, DTT, glycerol and several salts had the opposite effect. In addition, the influence of curing agents on glutaminase activity was investigated. Nitrate, nitrite, glucose and ascorbic acid had no significant effect on enzyme activity at the levels typically used in the processing of dry-cured sausages, while 1 M NaCl inhibited nearly 55% of the glutaminase activity.