Study On Screening Of Feed Multiple Enzyme High-yield Strains, Optimization Of Fermentation Conditions And Enzyme Properties

Through transparent circle screening, liquid-state fermentation and determination of enzyme activity, 92 strains producing phytase were acquired, and then through solid -state fermentation and determination of enzyme activity, a strain quite good at producing feed multiple enzyme -WP1 were screened out.Fermented on culture medium with bran as the main material, A. niger WP1 could produce abundant feed enzymes, including phytase, cellulose, xylanase, pectinase,β- glucanase, amylase and acid protease.The optimized solid-state fermentation conditions for A. niger WP1 was: the main material bran,ratio of material to water 10:8,adding 1.5% NaNO₃ and 1% SDS,culture temperature 28℃,initial pH of culture medium 6.0. Under such conditions, the acivities of main feed enzymes on the 6th day were: phytase 943 U/g, cellulose 3089 U/g, xylanase 651 U/g, amylase 508 U/g.Through solid-state fermentation, extraction, concerntration, mixing with excipient and drying, the multiple enzyme preparation were got. The activities of enzymes were respectively: phytase1000U/g, cellulase2817 U/g, xylanase881 U/g, pectinase 558 U/g,β-glucanase55 U/g, amylase1082 U/g, acid protease429 U/g cellulose, xylanase.The optimal temperature for phytase, cellulose, xylanase and amylase from WP1 to work were respectively 55℃, 70℃, 50℃and 70℃.Activity of phytase had two apices at ph 2.0 and 4.5 and the optimal pH of cellulose, xylanase and amylase were respectively 4.0, 3.5, 5.0.The activity of phytase still remains 87% after keeping at 55℃for 1 hour; activites of cellulose, xylanase and amylase remains 87%, 60% and 96% after keeping at 50℃for 2 hours. The activity of phytase remains 78.6% after keeping at pH 2.0 for 3 hours; activities of cellulose, xylanase and amylase remain basically the same after keeping at pH 2.0 for 6 hours.So it is concluded that the enzymes produced by WP1 had good heat stability and acid resistance. It adapted well to feed processing and environment in stomaches of animals and could be used in practical production.At last, the practical performance was tested in laying hens farm. On normal nutritional level, adding the feed multiple enzyme to the feed of laying hens shows good effect. Total egg productivity had increased by 9.67% ,normal egg productivity 8.15%, percent of average weight of eggs 1.64%, intensity of eggshell 6.58% and phosphor content in dejecta decreased by 31.65%.