Assessment of urea degradation rate in model wine solutions by acid urease from Lactobacillus fermentum.
The specific activity (piA) of a whole cell acid urease preparation was assessed in model wine solutions at different levels of malic (M) and lactic acids, metabisulfite, ethanol, and pH by performing a central composite design. M and then pH were found to be the most controlling variables, their effects being practically coincident but of opposite sign. For urea concentrations up to approximately 1 mol m(-3) the ammonium formation rate was assumed of the pseudo-first-order with respect to urea, this being confirmed by two independent validation tests performed at 20 degrees C for as long as 24 h. In the case of real wines the effective pseudo-first-order kinetic rate constants were found to be smaller than those pertaining to the model solutions having the same wine composition and pH by a factor varying from 10 to 1000, this affecting significantly the specific urease treatment costs per liter of wine treated.
Fidaleo
Marcello
M
Department of Food Science and Technology, University of Tuscia, Via San Camillo de Lellis, 01100 Viterbo, Italy.
Esti
Marco
M
Moresi
Mauro
M
D000431:Ethanol / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019344:Lactic Acid / Q000032:analysis; D052197:Limosilactobacillus fermentum / Q000201:enzymology*; D008293:Malates / Q000032:analysis; D015203:Reproducibility of Results; D012996:Solutions; D013447:Sulfites / Q000032:analysis; D014508:Urea / Q000378:metabolism*; D014510:Urease / Q000378:metabolism*; D014920:Wine / Q000382:microbiology*
D008293:Malates; D012996:Solutions; D013447:Sulfites; D019344:Lactic Acid; D000431:Ethanol; C030981:metabisulfite; C030298:malic acid; D014508:Urea; D014510:Urease