Research On Stability Of Phytase Transgenic Corn And Its Effect On Degradation Of Phytate Phosphorus

Supplementation of phytase in feedstuff can effectively improve phytate-Putilization of monogastric species. Experiments on monogastric animals havedemonstrated the equivalent activity of phytase transgenic corn in declining thephosphorus excretion by pigs and chicken. However, storage and thermostability ofPTC has thus far not been well studied. Furthermore, increasing researches haverevealed the deficiency of phytase in rumen of ruminant generated by the microbes.Therefore, it entails further studies as to decipher whether PTC can further improvethe availability of phytate phosphorus by ruminants.1Effect of conventional storage on phytase activity. PTC was stored inconventional condition and phytase activity was tested every three months.Comparative activity of phytase stored for eighteen months was81.5%compared tothat of six months. Therefore, PTC-derived phytase showed good stability afterlong-term storage.2Thermostability of PTC-derived phytase. PTC-derived phytase was treated byboth dry heating and wet heating methods. Completely random3×3block designwas employded and the two varying factors are temperature (100℃,120℃and140℃) and heating time (5min,10min and20min). Results: PTC-derived phytaseshowed good thermostability that only9.7%of phytase was lost following dryheating at100℃for5minutes compared to the45.68%loss after wet-heating.Therefore, wet heating exerted more influence than dry heating under the sameconditions.3Influence of extrusion on phytase activity. Completely random5×3blockdesign was employded and the two varying factors are extrusion temperature (60℃,70℃,80℃,90℃and100℃) and water supplementation (20%,24%and28%).Corn supplemented with coated exogenous phytase worked as the control (the same starting enzymatic activity). Results: increasing enzymatic activity loss by extrudingprocess was shown in the experiment with the temperature increment and morewater supplementation. Under the condition of20~28%water content and60~100℃extrusion temperature, the phytase activity loss of PTC and exogenous phytase were64.73~97.4%and75.1~99.2%, respectively. Phytase activity loss by extrusion onextraneous phytase was higher than that of PTC-derived phytase. There wasextremely significant different phytase activity loss between different watersupplementation and extrusion temperature (P<0.01) and extremely significantinteraction between these two factors (P<0.01).4Research on effect of PTC by artificial rumen method. Degradation effect ofphytate-P by PTC-derived phytase in artificial rumen was studied by AGRS-III invitro gas production recording device and software system. Result: Degree ofdegradation increased with the incubation time and supplementing levels of PTC.And moreover, PTC supplementation showed no significant effect on pH of rumenjuice and disappearance rate dry matter other than increasing gas production.