Table 5.

Ammonia and pH comparison of liquid versus lyophilized esterase^a

	Enzyme concentrationb
Measured parameter	0x	100x	500x
Liquid esterasec
pH	8.17	8.06	7.91
Total ammonia (mg/L)	0.3	15	73.8
Un-ionized ammonia (mg/L)	0.02	0.80	2.84
Lyophilized esterased
pH	7.90	8.42	8.42
Total ammonia (mg/L)	0.2	0.4	0.2
Un-ionized ammonia (mg/L)	0.01	0.05	0.02

^aValues were measured during toxicity studies with Hyalella azteca.

^b1x dilution = 2.3 × 10⁻³ U/ml. A unit of activity is the amount of enzyme that hydrolyzes 1.0 μmol of butyrate to butyric acid and ethanol per minute at pH 8.0 at 25°C (as defined by Sigma Chemical, St. Louis, MO, USA).

^cEnzyme was from an ammonium sulfate suspension from porcine liver (3.2 M, pH 8.0, lot 102K7062; Sigma Chemical).

^dEnzyme was from a crude lyophilized powder (lot 123K7033; Sigma Chemical).