Determination of Phytase Activity in Feed by a Colorimetric Enzymatic Method: Collaborative Interlaboratory Study

Abstract

Fourteen laboratories participated in a collaborative study (coded fyt9404) and 13 laboratories participated in a study (coded fyt9410) to validate a colorimetric assay for determination of microbial phytase activity in feed. For each study, all laboratories received 6 laboratory samples provided by one commercial supplier (phytase activity levels within the range of 200–400 per kg) to be analyzed in duplicate. Method performance was calculated and statistical calculations were executed according to AOAC guidelines. Results from 3 laboratories for study fyt9404 and from one laboratory for study fyt9410 were excluded from statistical analysis because of invalid data determined during initial review by Youden pair, value versus laboratory. For study fyt9404, repeatability relative standard deviation (RSDr) values ranged from 6.2 to 8.6%, and reproducibility relative standard deviation (RSDR) values ranged from 14.1 to 27.6%. No outliers were identified. For study fyt9410, RSDr values ranged from 3.9 to 7.9%, and RSDR values ranged from 14.0 to 20.5%. With outliers excluded, RSDr values ranged from 2.5 to 7.9%, and RSDR values ranged from 14.0 to 20.5%.

Efficacy of different commercial phytase enzymes and development of an available phosphorus release curve for Escherichia coli-derived phytases in nursery pigs12

“…These prescribed assay conditions were optimal reaction conditions for Aspergillus niger phytase. Engelen et al (2001) further modified the method for measuring phytase activity in animal feed. The revisions were simply the inclusion of additional steps for grinding and extracting feed samples before enzyme assay.…”

“…Phytase activities (FTU/kg) of the diets, pure phytase products, and premixes were analyzed using both the AOAC official method (2000( .12, AOAC, 2000Engelen et al, 1994Engelen et al, , 2001 and the Phytex method ; Table 4). The AOAC analysis was performed in multiple commercial laboratories (3 and 2 laboratories for Exp.…”

Effect of starter culture inoculation on feed hygiene and microbial population development in fermented pig feed composed of a cereal grain mix with wet wheat distillers’ grain

“…Freeze-dried samples were analysed to determine the phytase activity in the dry mix by the method of Engelen et al (2001). One phytase unit (PU) is the amount of enzyme that releases 1 lmol inorganic phosphate per minute from 5AE1 mmol l )1 of sodium phytate under experimental conditions (pH 5AE5, 37°C).…”

A genetically engineered Escherichia coli phytase improves nutrient utilization, growth performance, and bone strength of young swine fed diets deficient in available phosphorus1

“…The phytase premixes were analyzed for phytase activity (Engelen et al, 1994(Engelen et al, , 2001 before diet mixing. The phytase activities (triplicate analyses) were 2,844 phytase units (U)/g for the E. coli phytase, and 3,000 phytase U/g for the P. lycii phytase.…”

“…On d 28 of the experiment, the pigs were killed (stunned by captive bolt followed by exsanguination). One unit (U) of phytase activity is defined as the amount of enzyme that liberates 1 mol of inorganic P per min from 5.1 mM sodium phytate at 37°C and pH 5.5 (Engelen et al, 1994(Engelen et al, , 2001. Each mean represents 9 pens (experimental units) with 2 pigs in each pen.…”