Study On Technique Of Producing Dietary Fiber By Schizophyllum Commune Solide State Fermentation On Sweet Potato Residue And Design Of Bioreactor

As a by-product from srarch production and a potential source of dietary fiber, sweet potato residue is discarded and causes resource wasting and environmental pollution. In this study, the procedure of producing dietary fiber was investigated by S. Commune solide state fermentation and design of bioreactor. The main results were as follows:In order to determine dietary fiber by S.Commune solide state fermentation on sweet potato residue accurately, the international standard method was modified. The main points were as follows: scale test tube with stopper was used as an enzymatic reaction container; sample was treated by microwave for one minute before enzymatic reaction; glass wool was used as accelerating filtration. The exactitude of the improved method was below 6% and the recovery of total dietary fiber, insoluble dietary fiber and soluble dietary fiber was 99.6%,98.8%,103.7% respectively. The improved enzymatic-gravimetric method could be used to determine dietary fiber by S. Commune solide state fermentation on sweet potato residue.Optimal flask solide state culture condition was: wheat bran 4%, water 70%, strain age 4 d, inoculation volume 10%, culture time 16 d. Under the conditions, the average content of TDF,IDF and SDF reached 70.5%,54.6%,15.9% respectively. By studying the fermentation process, it was suggested that lignocellulose was degraded at the initial stage of fermentation. Then starch in the sweet potato residue was utilized by S. Commune in the form of reducing sugar with the enzymolysis of amylase and stach was decreased by 93.8% within the early 12 d. Dietary fiber of fermentation product was a complex formulation of sweet potato dietary fiber and S. Commune dietary fiber. The main components of insoluble dietary fiber were cellulose and hemicellulose.Studying on fermentation scale-up, the maximum penetration velocity of mycelium in solide state substrate was 15.673 mm/d under the optimal conditions: composition of particle size (250-425)μm 18.5%, (425-850)μm 45.8%, (850-2000)μm 13.9%, others 21.8%, water 65%, charging coefficient 69%, temperature 27℃and natural lighting. In the case, mycelium with different locations in substrate could penetrate to all direction simultaneously and it could overgrow in substrate within 3 d if strains and substrate were mixed sufficiently when inoculation. At 5 L solide fermentation level, with the extension of time, water content of surface substrate decreased and volume of substrate reduced. During the fermentation process, the some solution generated on the container wall and the average temperature of inside substrate was higher than that of outside container.According to the results of scale-up fermentation research the 70 L solide state bioreactor was designed and had advantages of determination and feedback control on line. Particularly, the bioreactor was applicable to filamentous fungi solide fermentation on tuber viroid residue.With the results showed above, the feasibility of this type of sweet potato residue procedure had been confirmed and presented a new effective pathway of comprehensive sweet potato residue process.