Abstract: Soybean dregs were used as the basal fermentation medium for Mucor to produce soluble dietary fiber (SDF). The effects of major parameters including water content in medium, initial pH, fermentation temperature and fermentation time were analyzed and the fermentation process was optimized by one-factor-at-a-time design (OFAT), fractional factorial design (FFD), central composite design (CCD) and response surface methodology. The optimal fermentation process conditions were 10 g of soybean dregs contained in a 250 mL shake flask with the addition of 2.33% peptone (g/g soybean dregs), 0.57% KH2PO4, 0.2% CaCl2 and 0.2% Tween-80 as the nutrient supplements, initial water content of 56.7%, fermentation temperature of 25 ℃ and fermentation time of 80 h. Under these conditions, the yield of SDF could reach up to 42.2%. Therefore, Mucor fermentation is applicable for the preparation of SDF from soybean dregs.

Key words: soluble dietary fiber, soybean dregs, Mucor, fermentation, preparation