Research On Dietary Fibre Of Millet Bran Fermented By Bacillussubtilis

Millet bran(MB)is the main by-product in the process of millet production and processing,which contained kinds of nutrition components,such as dietary fibre,protein,et al.But MB was mainly applied to fodders of livestock and poultry,it has not been fully exploited and utilized.Dietary fiber was the key component of MB which has been proved to have some physiological functions such as reducing blood glucose,decreasing blood lipid and intestinal diseases risk and boosting immunity,et al.It was a hot spot of current research that in order to improve utilization and addition by microbial fermentation of agricultural by-product.Microbial fermentation can be safety and reduce the toxic side effect of products.Also it can reduce the economic cost of production and the pollution to the environment.In the paper,MB was used as raw material,preparation of dietary fiber by Bacillus subtilis var.NattoD-3 fermentation method was studied.Meanwhile,the dietary fiber's physical and chemical characterisitics were studied also.The mainly results were as follows:1.Optimization of fermentation conditions for NattoD-3 to produce millet bran dietary fiber was carried out with the production of soluble dietary fibre(SDF)as the response value.Plackett-Buramn design was applied to select the significance factors influencing SDF production and the results showed that particle size,fermentation temperature,fermentation time were significant variables.Response surface methodolgy optimization design was conducted to further research based on the results from the PB experiment.The optimal fermentation conditions were as following:particle size 227.82,fermentation temperature 36.9?,fermentation time 46.72h.Under these conditions,the production of SDF was 13.41 ± 0.25%which was 5.9 times as the SDF yield of raw material(2.28%).2.The study of functional characteristics of dietary fibre from millet bran.Fermentative dietary fibre(F-DF)and enzymatic dietary fibre(E-DF)were prepared by Bacillus subtilis var.NattoD-3 fermentation and AOAC method.Compared with E-DF,when dietary fibre was fermented,there was a significant increase in TDF(75.64%to 79.74%)and SDF(2.28%to 13.21%)content.The ratio of soluble to insoluble dietary fibre was increased from 3.11 to 19.86.F-DF was used for furher functional research.Results revealed that the water holding capacity,swelling power and the adsorption capacity for soybean oil of F-DF were 4.34g/g,3.51mL/g and 3.32g/g,respectively.The adsorption capacity of cholesterol of F-DF was depended on pH.At pH 7.0,its adsorption capacity of cholesterol was 14.26mg/g,the value was bigger than that at pH 2.0,its adsorption capacity of cholesterol was 9.15mg/g.The adsorption capacity of NO2-of fermentation products was still depended on pH.At pH 2.0,its adsorption capacity of NO2-was 4.61ug/g,the value was higher than that at pH 7.0,its adsorption capacity of NO2-was 0.72ug/g.Otherwise,F-DF had high adsorption capacity for cation.The value of SWC,WHC,the adsorption capacity of cholesterol,NO2-and glucose of F-DF were higher than the value of E-DF.Under the same condition,the DPPH free radical scavenging capacity of F-DF was higher than that of E-DF.All of these results explained that F-DF had greater physiological functions than E-DF and was a meaningful substance for research.3.The physicochemical studies on E-DF and F-DF.The physicochemical studies on E-DF and F-DF such as monosaccharide compositions,FTIR spectrum,microstructure demonstrated that fermentation changed the saccharide composition of dietary fibre.The increase in SDF produced by fermentation was apparently due to a reduction of insoluble polymers containing arabinose,xylose.Moreover,the results showed that fermentation resulted in the modification of the fibrous structure.These physicochemical changes might closely relate to the high absorption capacity of F-DF in vitro.Therefore,preparation of dietary fiber by Bacillus subtilis NattoD-3 fermentation method could be considered a good method to improve the production of SDF and the functionality of dietary fibre.