Characteristic Of Enzyme Production Of Bacillus Velezensis And Its Application To Laying Hens Feed

Probiotics can promote the growth and production performance of animals,which may act through secreting enzymes.A strain of bacteria was isolated from the manure of piglets,and identified as a kind of Bacillus velezensis,named as B.velezensis Y1 through analysis the gene sequence of 16S rDNA.Its proper fermentation conditions of cellulase production were studied by single-factor experiment and orthogonal test.The results indicated that the optimal fermentation conditions of cellulase were temperature of 37℃,time of 60 h,initial pH of 7.0,outfit fluid amount of 50 mL/250 mL.And the order of the effect of various factors on the ability of producing enzyme by B.velezensis Y1 was:temperature>time>pH>outfit fluid amount.The study of some properties of the cellulase from B.velezensis Y1 showed that the optimal reaction temperature was 65℃ and the optimal pH of the enzymes was 6.0.The enzyme possessed strong resistance against heat,acid,alkali and preferable selectivity to some cellulose substrates.The K+ and Ca2+ enhanced cellulase activity,while the Zn2+,Mg2+,Mn2+,and Al3+ inhibited cellulase activity.The effect on the replacement of Bacillus velezensis for antibiotics in laying hens was also studied by adding different does of B.velezensis in the laying hens feed.A total of 468 Hy-Line Browns hens(49-week-old)were selected and randomly divided into four treatments with three replicates including the control group(basal diet),experiment group Ⅰ(adding 1.0×1010 CFU/kg B.velezensis to basal diet),experiment group Ⅱ(adding 2.0×1010 CFU/kg B.veleznesis to basal diet),and antibiotic group(adding 50 mg/kg flavomycin to basal diet).The egg quality was determined on the 21st and 42nd day in the whole period.The results were as follows:(1)Compared with the control group,the average egg production rate,average daily feed intake of experiment groups increased significantly(P<0.05),but the effect of antibiotic group was better than the two experiment groups.The feed/egg ratio of both groups was reduced,but not significantly.(2)Compared with the control group,the results of the first determination showed that the egg weight,egg shape index,eggshell strength,and eggshell weight in both groups was slightly decreased,and the eggshell color,yolk weight,yolk color,albumen height,and Haugh unit was increased,but not significantly.The results of the second determination indicated that the egg weight and eggshell weight was decreased,while the eggshell strength and eggshell color of the experiment group Ⅰ was increased,also not significantly.The yolk weight of the experiment group Ⅱ was increased,but that of the antibiotic group and experiment group Ⅰwas slightly decreased,neither significant.The eggshell strength,yolk color,albumen height and Haugh unit was significantly increased(P<0.05).(3)Supplementation with B.velezensis with 1.0×1010 CFU/kg and 2.0×1010 CFU/kg could increase the progesterone and motilin,but decrease the secretin and cholecystokinin in the blood serum(P>0.05).On the whole,the effect of experiment group Ⅱ was better than experiment group Ⅰ.To a certain extent,B.velezensis can replace the feed antibiotics which has good application value.This experiment provides a practical basis for the application of Bacillus velezensis to laying hens feed instead of antibiotics.