The Mechanisms Of Feruloylated Arabinoxylan In Regulating Intestinal Flora

The intestinal flora is closely related to human growth and development,nutritional metabolism,and health.The main components of whole grains that improve host health by modulating gut microbiota are concentrated in the bran.Grain bran is rich in dietary fiber and phenolic acids,arabinoxylan(AX)is a common semi-cellulose in grain bran.AX often form feruloyl arabinoxylan(FAX)with feruloylated esters,and the feruloyl groups on the branches could improve the antioxidant activity of FAX.In addition,phenolic acids are the important groups to crosslink the cellulose,semi-cellulose,and other cell wall components,which could maintain the structure of the cell wall of grain bran.However,the effects of phenolic acids in the fiber and grain bran are unclear.Therefore,this article uses the main semi-cellulose and rice bran of the grain bran as raw materials,then explore the role of phenolic acids in the process of FAX and rice bran in regulating the intestinal flora.The main experimental contents and results are as follows:(1)To investigate the effect of feruloyl groups content on the intestinal probiotic properties of FAX:Through the identification of FT-IR and ~1H NMR,three FAX with different feruloyl groups contents of 80.75 mg/g(HAX),50.40 mg/g(MAX),and 0.20mg/g(LAX)were successfully synthesized.The basic components,neutral sugar and uronic acid composition and XRD analysis showed that the three FAX had no significant difference in polysaccharide structure,only the content of feruloyl groups was different.In vitro fermentation,the content of feruloyl groups affected the fermentation characteristics of FAX.Compared with LAX,the total short chain fatty acid salts(total SCFAs)produced by HAX and MAX were not significantly different after fermented,but the butyrate production was both significantly lower.Although the contents of feruloyl groups in HAX and MAX were different,the antioxidant capacity of their fermentation broth was significantly higher than that of LAX,and there was no significant difference between them.Although the contents of feruloyl groups in HAX and MAX were different,the antioxidant capacity of their fermentation liquid was significantly higher than that of LAX,and there was no significant difference between them.The three FAX promoted the growth of Bacteroides within 12 h,promoted the growth of Paraprevotella within 24 h,and inhibited the growth of Feacalibacterium and Roseburia.The effects of FAX with different feruloyl groups contents on the alpha diversity of the flora were significantly different.In addition,with the increase content of feruloyl groups,FAX inhibit the growth of harmful bacteria(Dialister,Alistipes,and Desulfovibrio),and promote the growth of symbiosis/probiotics(Prausereella,Akkermansia,Psychrobacter and Paraprevotella).The above results show that feruloyl groups significantly affect the regulation of FAX on intestinal flora,and the higher the content of feruloyl groups,the more beneficial it is to improve the antioxidant capacity of fermentation liquid,maintain the alpha diversity and promote the growth of symbiotic/probiotic bacteria.(2)Comparing the effects of polysaccharide structure and feruloyl group of AX on its intestinal probiotic properties:Rice bran arabinoxylan(RAX)and corn bran arabinoxylan(CAX)were extracted from rice bran and corn bran,respectively,and their feruloyl groups content was 0.98 and 1.05 mg/g,respectively.d RAX and d CAX were gain by ferulic acid esterase treatment with the feruloyl contents of 0.12 and 0.14mg/g.The arabinose/xylose molar ratio and molecular weight of CAX are lower than those of RAX,and it has less branched structure.In vitro fermentations,the gas production,total SCFAs,acetate,and propionate,and the antioxidant capacity of fermentation liquid of CAX were significantly higher than RAX,but butyrate was significantly lower,while ferulic acid esterase removed feruloyl groups did not significantly affect the fermentation characteristics of these two AX.Both AX can promote the growth of Bacteroides and inhibit the growth of Feacalibacterium,and CAX has a more significant effect than RAX,while the remove of feruloyl groups has no significant effect on this effect.Both AX fermentations reduced the alpha diversity of the flora,with RAX reducing the diversity more significantly than CAX,and the diversity was significantly changed after removal of the feruloyl group.Therefore,the ability of AX to regulate the intestinal flora is mainly affected by the polysaccharide structure of AX(branching degree and molecular weight,etc.),although the removal of feruloyl groups has no significant effect on the fermentation characteristics and the overall flora of AX,it has an effect on the decrease of the alpha diversity of the flora after AX fermented.(3)To investigate the effect of structure in rice bran on its intestinal probiotic properties:By alkaline hydrolysis of rice bran(RB),the connection between the phenolic acid and the components forming the cell wall structure is broken,and the phenolic acid and the components forming the cell wall structure are dissolved to obtain the full component(a RB)and the soluble component(sa RB))and the insoluble fraction(ia RB),where a RB contains free phenolic acids and insoluble and soluble dietary fiber,sa RB contains soluble dietary fiber and free phenolic acids,and ia RB contains insoluble dietary fiber.The connection between the phenolic acid and the components forming the cell wall structure of rice bran(RB)is broken after hydrolysis RB with alkaline,and the phenolic acid and the components forming the cell wall structure are dissolved to obtain the full component(a RB)and the soluble component(sa RB))and the insoluble fraction(ia RB),where a RB contains free phenolic acids and insoluble and soluble dietary fiber,sa RB contains soluble dietary fiber and free phenolic acids,and ia RB contains insoluble dietary fiber.The total SCFAs and the antioxidant capacity of fermentation liquid were significantly higher in a RB,sa RB and ia RB compared with RB.RB had a promoting effect on the growth of Bacteroides and Paraprevotella,and the effect of a RB and sa RB was more significant,indicating that the dissolution of the components that form the cell wall structure of RB would enhance this effect.RB had no significant effect on the growth of pathogenic bacteria Shigella,while the three components after alkaline hydrolysis significantly inhibited the growth of Shigella.The above results showed that the dissolution of the components forming the cell wall structure was beneficial to promote the production of SCFAs after RB fermented,improve the antioxidant capacity of the fermentation liquid and inhibit the growth of pathogenic bacteria Shigella.In conclusion,FAX with higher content of feruloyl groups,the more beneficial it is to improve the antioxidant capacity of the fermentation liquid and promote the growth of symbiotic/probiotic bacteria.However,the effect of feruloyl groups on the ability of FAX to modulate gut microbiota was weaker than that of polysaccharide structural properties(degree of branching and molecular weight,etc.).In addition,the connection between the phenolic acid and the components forming the cell wall structure of grain bran is destroyed,the phenolic acid and the components of the cell wall structure are dissolved,which is beneficial to improve the intestinal probiotics of the grain bran.