Research On Preparation Of Dietary Fibre Of Wheat Bran By Solid State Fermentation With Bacillus Natto

As one of the by-products of wheat processing,wheat bran is rich in nutrients and it contains a large number of physiologically active substances.China's wheat bran is rich in resources but has not received enough attention,and its economic value has not been effectively exploited.Dietary fibre has an important physiological role in maintaining human health and the percentage of dietary fibre in wheat bran is high.But the conventional method of preparing dietary fibre has the disadvantages such as low dietary fibre yield and environmental pollution.So it is not suitable for large-scale production.By using the method of microbial fermentation to increase the content of soluble dietary fibre in the extracted dietary fibre can significantly improve the physiological activity of dietary fibre of wheat bran.Besides,bacillus natto can be safety and efficient to ferment wheat bran to prepare dietary fibre.Therefore,carrying out research on the fermentation conditions and process optimization of dietary fibre of wheat bran fermented by bacillus natto and research on the functional characteristics of dietary fibre of wheat bran have practical significance.It is also of great significance for the development and utilization of wheat bran resources.In this paper,wheat bran was used as raw material.The optimization of the process conditions for preparing dietary fibre by fermenting wheat bran using Bacillus subtilis var.NattoD-3 and the physicochemical properties of dietary fibre of the fermented wheat bran was studied.The main research contents are as follows:1.Optimization of fermentation conditions of dietary fibre by fermenting wheat bran by NattoD-3.A single factor test was used to examine the content of soluble dietary fiber(Soluble Dietary Fibre,SDF)and insoluble dietary fiber(Insoluble Dietary Fibre,IDF)in fermented wheat bran by medium-liquid ratio,inoculation amount,fermentation time,particle size and fermentation temperature.Based on the results of the single factor test,the effects of various factors on the content of SDF in the dietary fibre of fermented wheat bran were studied by Plackett-Buramn(PB)test.The experimental results showed that the effects of inoculation amount,fermentation time,particle size and fermentation temperature are significant.However,due to the limitation of the screen specifications,the average particle size cannot be accurately controlled.Therefore,fermentation temperature,fermentation time,and inoculation amount were selected as factors for central composite design-response surface method optimization.The optimal conditions were as following:10:15 of solid/liquid ratio,11.15%of inoculating amount,34.56? of fermentation temperature,56.72h of fermentation time,and 0.34 mm of the average particle size.Under these conditions,the SDF content in dietary fibre of fermented wheat bran was 167.86 mg/g,which was about 4.27 times higher than the SDF content of unfermented wheat bran(38.86 mg/g).2.Analysis of the content changes of fermented wheat bran and its dietary fibre.The content changes of conventional components and functional components such as reducing sugar and soluble polysaccharide and the changes in fibre composition of F-DF and E-DF were compared and studied.Experimental results of the components after fermented found that the content of protein and starch in wheat bran decreased significantly,and the total dietary fibre content increased significantly.The content of reducing sugar and soluble polysaccharide in fermented wheat bran increased.In addition,the phytic acid content in wheat bran decreased significantly after fermentation.Experimental results of the components of the prepared E-DF and F-DF showed that the proportion of soluble dietary fibre in F-DF increased,the proportion of insoluble dietary fibre decreased,and the contents of cellulose,hemicellulose and lignin all decreased.3.Experimental study on the functional characteristics of dietary fibre of wheat bran.The water-holding capacity,oil-holding capacity,swelling power,adsorption characteristics and total phenol content of E-DF,F-DF,soluble dietary fibre(F-SDF)and insoluble dietary fibre(F-IDF)in dietary fibre of fermented wheat bran were comparatively studied.The experimental results showed that compared with E-DF,the water holding capacity and swelling capacity of F-DF were significantly improved,and the water holding capacity and swelling power reached 3.51 g/g and 2.81 mL/g.In addition,compared with E-DF,F-DF also showed better adsorption of fat-soluble substances,and its adsorption characteristics of soybean oil was 1.82 g/g.F-DF has a stronger adsorption capacity of glucose than E-DF,about 54.23 mg/g.At pH 7.0(small intestine environment),the adsorption capacities of cholesterol of F-DF and E-DF were 10.64 mg/g and 8.68 mg/g,which are significantly better than those in pH 2.0(the stomach environment).At pH 2.0,the experimental results showed that the absorption capacity of dietary fibre for nitrite ions in the stomach(pH 2.0)environment is higher than that in the small intestine(pH 7.0)environment,and the adsorption capacity of nitrite ion of F-DF was stronger than that of E-DF.In addition,the total phenol content of dietary fibre before and after fermentation was studied by experiments.The results showed that the fermentation could effectively increase the total phenol content in dietary fibre of wheat bran.The total phenol content of E-DF was 1.47 mg/g,and the total phenol content of F-DF after fermentation was 4.30 mg/g.In summary,by using of Bacillus subtilis var.NattoD-3 to ferment wheat bran can significantly improve the percentage of SDF in dietary fibre of wheat bran under the best fermentation conditions.Thus,the physiological activity of dietary fibre can be better utilized.