The Machanisms Of Arabinoxylan-specific Degrading Enzymes Improving Lactobacillus Proliferation In The Gut Of Broliers

Lactobacillus is a main kind symbiotic bacteria in the gut of livestock and plays an important role in the regulation of the gut health.Xylan oligosaccharides(XOS)is the hydrolysates of arabinoxylan(AX)and shows a better proliferative effect on Lactobacillus.Previous studies indicate that the prebiotic effects depend on the sutrcture of XOS.However,the relationship between the structure and prebiotic effects of XOS is still not classified.Thus,four experiments were conducted to elucidate the mechanism of XOS produced by sepefic-AX degrading enzymes on the regulation of growth perfoamance and gut health regulation of broilersExperiment.1 The synergistic effect between xylanase and debranching enzymes on the hydrolysis of AX was researched.The hydrolysis efficiency of water extractable arabinoxylan(WE-AX),water un-extractable arabinoxylan(WU-AX)and beechwood xylan were improved with the extra supplementation of arabinofuranosidase(ABF)and feruloyl esterase(FAE)compared to xylanase used alone and resulted an increasing of released reducing sugars.A better synergistic effect wasobserved when extra ABF and FAE was used on the hydrolysis of WE-AX and WU-AX compared to xylanase used alone,which resulted an increased production of 72%and 36%reducing sugar,respectively.A more effective hydrolysis result was obtained when ABF and FAE were used to hydrolyze WU-AX and beechwood xylan prior to xylanase,which resulted in the production of reducing sugar 72%and 36%higher than xylanase alone.The production of XOS was increased 56.38%,46.06%,137.65%and 46.52%,53.03%,94.66%when ABF,FAE used alone and together combined with xylanase on the hydrolysis of WE-AX and WU-AX,respectively.Both XOS from WE-AX and WU-AX showed a more proliferative effect on Lactobacillus brevis compared to FOS and glucose(P<0.05).Experiment.2 The experiment was conducted to evaluate the synergistic effect of xylanase and debranching enzymes on AX hydrolysis in vivo.A total of 480 AA+ male broilers were divided into 5groups:control(CT)treatment,xylanase treatment(X),xylanase plus ABF(X+A),xylanase plus FAE(X+F)and xylanase plus ABF and FAE(X+A+F).Results showed that the average daily gained body weight(ADG)of broiler from 1-21 d and 1-36 d were both improved and feed/gain ratio were decreased when xylanase used(P<0.05).Extra supplementation of ABF and FAE could further improve the effects.The ADG and FCR were significant higher and lower in X+A+F group compared to xylanase group.A synergistic effect was observed on lowing the chyme viscosity in jejunum and Escherichia coli counts in the cecum,increasing Lactobacillus counts and xylan hydrolysis efficiency of broilers on d 36 when ABF and FAE were combination with xylanase.Experiment.3 The experiment was conducted to study the potential mechanism of specific AX-degrading enzymes on Lactobacillus proliferation in the gut of broilers.A new Lactobacillus strain was isolated from the cecum of broilers in experiment 1.The strain was identified as Pediococcus acidilactic and named BCC-1 through 16S rDNA sequence and biochemical methods.de-novo sequence results showed that BCC-1 consists of one chromosome and two plasmids,which were included by NCBI and the accession number are CP018763?CP018764 andCP018765.The effects of XOS and xylose supplementation on gene expression of BCC-1 were detected.Transcriptomic results showed that 1092 significantly differentially expressed genes(DEGs)were identified in XOS treatment compared to control group(no carbohydrate)and consists of 559 up regulated genes and 533 down regulated genes.376 DEGs were obtained in XOS treatment compared xylose treatment and consists of 200 up regulated genes and 176 down regulated genes.Compared to xylose treatment,5 significant enriched GO terms were identified in XOS treatment,including organic substance transport,carbohydrate metabolic process,phosphoenolpyruvate-dependent sugar phosphotransferase system,hydrolase activity,hydrolyzing O-glycosyl compounds,hydrolase activity,acting on glycosyl bonds.In contrast to xylose treatment,4 up regulated DEGs in XOS treatment belong to phosphate-dependent ABC transporters and 8 up regulated DEGs are related to carbohydrate metabolism,including tricarboxylic acid cycle,pyruvic acid metabolism and pentose phosphate pathway.Experiment.4 The experiment was conducted to study the effect of Pediococcus acidilactic BCC-1 supplementation on the growth performance and composition of bacteria in the gut of broilers.Compared to control group,both XOS and BCC-1 addition improved body weight gain(BWG)and feed intake and decreased F/G(P<0.05)of broilers on d 21.The combination of XOS and BCC-1 further improved these effects.Both XOS and BCC-1 significantly decreased pH value in the cecum(P<0.05)compared to control group,while BCC-1 could also decrease the chyme viscosity in the jejunum(P<0.05).The combination of BCC-1 and XOS further decreased the chyme viscosity in the jejunum compared to BCC-1 used alone(P<0.05).Compared to control group,the combination of XOS and BCC-1 improved the concentration of butyrate of the cecum chyme(P<0.05),ileum villus height(P<0.05)and villus/crypt depth value(P<0.05)and decreased the muscular thickness of ileum(P<0.05).16S rDNA sequence results indicated that both XOS and BCC-1 improved the bacteria diversity of cecum and the ratio of Firmicutes to Bacteroidetes.Transcriptomics results showed that big differences were observed in the cecum chyme components in each group.Compared to control group,XOS and BCC-1 supplementation improved the inositol and 4-hydroxyphenylpyruvic acid concentration in the cecum(P<0.05).Compared to XOS and BCC-1 treatment,the concentration of 5-hydroxyindole-3-acetic acid and gluconic acid were significantly higher when XOS was combined with BCC-1,respectively.The results indicated that the combination of ABF,FAE and xylanase specific to AX improve the hydrolysis of AX and XOS production.XOS produced a proliferative effect on Lactobacillus through up regulating the expression of genes encoded ABC transporter and key genes involved in the carbohydrate metabolism in Lactobacillus,which is beneficial for improvment of growth performance and gut health of broiles.