Abstract: Destarched bracken roots were solid-state fermented with Ganoderma lucidum and the fermentation residue was harvested and submitted to enzymatic hydrolysis and subsequent absolute ethanol precipitation to obtain soluble dietary fiber (SDF). The amounts of destarch bracken roots and water in fermentation medium and culture temperature were identified as main factors that influence SDF yield, and optimized by response surface methodology combined with central composite design. The results showed that the optimum amounts of destarch bracken roots and water in fermentation medium and culture temperature were 84%, 63% and 27 ℃, respectively. Under these conditions, the predicted and experimental values of SDF yield were 13.034% and 12.885%, respectively. The fact that they were not significantly different demonstrated that the developed regression model could experimental data well and was qualified. Moreover, the experimental value of SDF yield (12.885%) was significantly higher than the value of 1.733% obtained without Ganoderma lucidum fermentation before enzymatic hydrolysis.

Key words: destarched bracken roots, Ganoderma lucidum, fermentation process, solid-sate, soluble dietary fiber