Study On Oligosaccharide From Soybean Residue Fermented By Neurospora Crassa

In this research, the oligosaccharides from fermented soybean reside were studied. Soybean residue, the byproduct of processing soybean products, was used as raw material for fermentation. The Neurospora crassa strain which was isolated from the traditional fermented food in Jiangxi province was used for fermentation because of its high production of both cellulase and β-carotenoid. The changes of nutrition components during the fermentation process were analyzed and focused on the studies of oligosaccharides extracted from soybean residue after fermented by Neurospora crassa. The extraction conditions of oligosaccharides from fermented soybean residue were studied and optimized. Isolation and purification technologies for crude extract fluid of oligosaccharides were studied, and the oligosaccharide’s compositions were analyzed. In order to know the functions of such oligosaccharides, a technology of in vitro fermentation was used to estimate the physiological functions of it, so that this research can provide supports for further exploitations and applications of it. Main results are shown as followed:1. During the fermentation process, the recovery rate of fermented soybean residue was decreased and then kept on stabilization after48h. The degradation rate of crude fiber and the crude protein content were increased along with fermentation processing, and were stabilized after40-48h. The crude fats and carotenoids were increased in initial to reach to a peaking content and then declined later, but the crude fats were decreased to stationary state in the end. The total soluble sugar was increased in preliminary stage to a maximum content and then decreased gradually. When reached to a minimum content, the total soluble sugar was increased again and then stabilized after48h.2. Single factor tests and orthogonal tests were applied to increase the yield of oligosaccharides from fermented soybean residue, and the optimized conditions were as follows:the ratio of material to liquid was1:25, extracted for90min, the temperature of extraction was70℃, the ethanol concentration was50%and extracted for twice. After this optimized process,11.91%of oligosaccharides were extracted from fermented soybean residue.3. In order to purify the crude extract solution of soybean residue oligosaccharides, the method according to Sevag was used to remove protein, and AB-8macroporous resin was used to decolourization. The results indicated that the protein removal rate was67.21%, decolourization rate was62.41%, and the residual rates of oligosaccharides were95.98%and91.22%, respectively. These methods can purify the oligosaccharides effectively. After purification, the oligosaccharides were separated by high performance liquid chromatography and got2fractions, fraction A and fraction B. The fractions were analyzed by HPLC-ESI-MS and FT-IR, to determine the compositions of oligosaccharides. The results showed that fraction B has the deprotonated molecular ion peak which was m/z341, the peak was created by the process of disaccharide reduced a proton. There were some characteristic absorption peaks of saccharide in the FT-IR spectrum, and874.6cm-1was the characteristic absorption peak of beta C-H deformation vibration of pyranose. Therefore, fraction B was cellobiose definitely.4. The oligosaccharide samples after isolation and purification were tested by in vitro fermentation to estimate the fermentation characteristics. It was found out that the gas production with oligosaccharides at the concentration of800mg/L (7.25±0.16mL) was obviously lower than those of the control group (7.98±0.42mL)(P＜0.05), and was obviously higher than those of the glucose group (6.49±0.44mL)(P＜0.05). The oligosaccharides from fermented soybean residue have good fermentation characteristics. The pH of parts of oligosaccharide groups (4.95-5.00) were obviously lower than those of the control group (5.03±0.03)(P＜0.05), and when the concentration of oligosaccharide reached800mg/L, it has the lowest pH which was4.95. With the increasing of the mass concentration of oligosaccharide, the ammonia N content was declining, and the lowest content of ammonia N was recorded when the oligosaccharide group was at the concentration of1g/L, which was27.32±7.69mg/L. The oligosaccharide group of800mg/L was inoculated intestinal feces produced the highest content of acetic acid, reached114.81μmol/mL, and it also produced the highest amount of the total shot chain fatty acid(SCFA), which was226.37μmol/mL.